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International Review of Electrical Engineering Vol. 7 N. 2-- Part A
International Review of Electrical Engineering Vol. 7 N. 2-- Part B
International Review of
Electrical Engineering - April 2012 (Vol. 7 N. 2)
- Papers Part A
International Review of Electrical Engineering - Papers- Part A
Soft Switching Converter Without Output Inductor for Renewable Energy
Applications
by Bor-Ren Lin,
Po-Jen Cheng
Vol. 7. n. 2, pp. 3676-3684
Abstract - A soft switching converter without output inductor for renewable energy applications is presented in this paper to achieve the functions of MOSFETs zero voltage switching (ZVS) turn-on, low switching losses, low current stresses of transformer windings and high output voltage. Full-bridge converter with phase-shift pulse-width modulation (PWM) is adopted to regulate the output voltage and to realize the ZVS turn-on for all active switches. The voltage stress of power switches is clamped to DC bus voltage. Four transformers are connected in series and parallel in the primary side to reduce the current stresses of transformer windings. Each transformer can be operated as an inductor to smooth the output current or a transformer to achieve electric isolation and power transfer from input side to output side. Therefore no filter inductor is needed in the secondary side. Experiments based on a 960W laboratory prototype are provided to demonstrate the performance of proposed converter.
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Keywords: Soft Switching, ZVS, Full-bridge, Phase-shift PWM.
Two-Phase Interleaved Zero-Voltage-Switching Boost Converter with Coupled
Inductors
by Hyun-Lark Do
Vol. 7. n. 2, pp. 3685-3690
Abstract - A two-phase interleaved zero-voltage-switching (ZVS) boost converter with coupled inductors is proposed in this paper. In the proposed converter, two identical ZVS boost converters are paralleled and operate with interleaved control signals. By interleaving operation, current ripples at input and output stages are reduced. Due to the ZVS characteristic, the switching loss is significantly reduced and the efficiency is improved compared with the conventional two-phase interleaved boost converter. Steady-state analysis for the proposed converter is presented. Experimental results based on a 200 W (86V / 2.33A) prototype are provided to verify the effectiveness and feasibility of the proposed converter.
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Keywords:
Boost Converter, Coupled Inductor, Interleaved Converter,
Zero-Voltage-Switching, Zero-Current-Switching.
Interleaved
Soft Switching Zeta-Flyback Converter
by Bor-Ren Lin,
Bo-Ren Hou
Vol. 7. n. 2, pp. 3691-3698
Abstract - An
interleaved soft switching DC/DC converter for high DC voltage
applications is presented. In order to reduce the voltage stress of
active switches for high input voltage, two half-bridge converters are
connected in series at the high voltage side. Thus the voltage stress of
active switches can be clamped at one-half of input DC voltage. The
asymmetric pulse-width modulation (PWM) is adopted to control power
switches. With the resonant behavior by the leakage inductance of
transformer and the output capacitance of MOSFET at the transition
interval, active switches can be turned on at zero voltage switching (ZVS).
For each half-bridge converter, the zeta and flyback topologies are
adopted to share power components in the transformer primary side, to
achieve the partial magnetizing flux reset and to distribute load
current. The interleaved PWM scheme is used to control two converters
such that the ripple currents at output side are naturally reduced.
Therefore the output capacitances can be reduced. Experimental results,
taken from a laboratory prototype rated at 1kW, input voltage of
480~580V, output voltage of 48V, and switching frequency of 100kHz, are
presented to demonstrate the converter performance.
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Keywords: Asymmetric PWM, Interleaved PWM, ZVS.
Impedance
Criterion Based Virtual Inductor Control Method for Improving Inverter System
Stability
by Shigong
Jiang, Wei Wang, Dianguo Xu, Guihua Liu, Panbao Wang
Vol. 7. n. 2, pp.
3699-3708
Abstract - As the energy market increased, microgrid becomes a reliable application of renewable energy source. In the microgrid, inverter behavior is a significant concern to assure system operation reliability. The modeling of a traditional voltage source inverter system and its equivalent output impedance are set up, open loop stability and the boundary condition are represented in this paper. With the output impedance model, impedance stability criterion is employed to assess system stability. Furthermore, filter parameters impacts to the output impedance and system stability are certified by time-domain anslysis approach. Based on the negative incremental impedance characteristic, an AC constant power load model is described to study the degeneration of system stability by impedance specification approach. In order to damp the inverter equivalent output impedance and improve system stability, a virtual inductor control method, which is used to decrease the equivalent filter inductor, is proposed. With this method, the system dynamic response is enhanced and harmonic component at switching frequency is effectively suppressed. The availability of the proposed method is verified by simulation and experimental results.
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Keywords: Inverter, Stability, Output Impedance, Impedance Stability Criterion, Constant Power Load, Virtual Inductor Control.
Improved
Predictive Direct-Power-Control of Offshore VSC-HVDC Converter Without PLL
Scheme
by Shuang Li,
Zhixin Wang, Guoqiang Wang
Vol. 7. n. 2, pp.
3709-3716
Abstract - In this paper, a developed direct power control (DPC) strategy without the phase-locked loop (PLL) scheme is presented. The new system is based on predictive control theory to achieve the deadbeat control of instantaneous power for the voltage source converter (VSC). Theoretical principles of proposed predictive-based DPC (P-DPC) strategy are discussed. The operation and performance of this P-DPC system are illustrated both in steady-state and dynamic behavior. It is shown that the P-DPC exhibits several advantages, particularly no needing to detect the position of voltage vector, without complex coordinate transformation. Both simulation and experimental results show the excellent performance and verify the validity of the proposed control methods. It also provides an available control strategy for offshore VSC-HVDC engineering.
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Keywords: Predictive Direct-Power-Control (P-DPC), Instantaneous Power, Offshore Wind Farm, Voltage Source Converter (VSC), VSC-HVDC, pulse width modulation (PWM), digital signal processor (DSP).
Soft-switched
High Step-up Converter with Ripple-free Input Current
by Hyun-Lark Do
Vol. 7. n. 2, pp. 3717-3724
Abstract - A soft-switched high step-up converter with ripple-free input current ripple is presented. In the presented converter, the coupled-inductor is utilized to cancel out the input current ripple. The DC-DC converter cell with N-stage voltage doubler in the proposed converter provides soft-switching characteristic of main switches and alleviates the reverse-recovery problems of the output diodes. The proposed converter achieves high efficiency because of reduction of the switch voltage stress, mitigation of the output diodes’ reverse recovery problem, and soft-switching characteristic of main switches. Detailed analysis and design of the proposed converter are carried out. A prototype of the proposed converter is developed, and its experimental results are presented for validation.
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Keywords: Step-Up Converter, Soft-Switching, High Voltage Gain, Zero-Voltage-Switching.
Fast-Response Soft-Switching High-Voltage DC–DC Converter with Wide Range of
Controllability
by Sze Sing Lee,
Shahid Iqbal, Mohamad Kamaro
Vol. 7. n. 2, pp. 3725-3732
Abstract - Wide range of control and quick dynamic response of output voltage is essential for high-voltage X-ray power supplies, especially for medical imaging applications. To address the former issue, a new control technique in which both capacitance of tank circuit and switching frequency of inverter is modulated was proposed in [18]. The technique was shown to have several benefits such as wide range of control even at light load, low output voltage ripple, and less current stress on the inverter’s power switches at light load, etc. However, it did not address the issue of dynamic response. To resolve the issue, this paper proposes a dual-mode pulse frequency modulation control at start-up of the converter. In this operation, the inverter is started at a high switching frequency (fstart), and as the output voltage reaches 90% of the target value, the switching frequency is reduced to a value which corresponds to the target output voltage. This can effectively reduce the rise time of output voltage and prevent overshoot. The performance of the proposed control scheme is verified by the experimental results of a scale-down laboratory prototype.
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Keywords: Control Scheme, DC-DC Converter, Dual-mode PFM.
A Constant Frequency Current Control Scheme for H-Bridge Grid-Connected Voltage
Source Inverters
by M. Saleh, A.
Shoulaie
Vol. 7. n. 2, pp.
3733-3738
Abstract - In this paper a simple and robust current control scheme for H-bridge grid-connected voltage source inverters is proposed. This scheme provides fast transient response quite similar to conventional hysteresis current control, while retaining switching frequency at a constant value over a line cycle. Switching times are predicted using simple mathematical relations and applied to the voltage source inverter. Furthermore, this scheme can be easily implemented using digital controllers. The steady state and transient performance are studied via simulation and experimental tests, which are in good agreement and validate the robustness and excellent performance of the proposed scheme.
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Keywords: Grid-Connected Voltage Source Inverter, Current Control, Constant Switching Frequency.
Accurate and Fast Reference Signal Estimation with Averaged-LMS for Active Power
Filters
by M. Cakir
Vol. 7. n. 2, pp.
3739-3748
Abstract - In this paper, an Averaged-Least Mean Squares (A-LMS) based reference extraction method for active power filter (APF) is proposed. With A-LMS, high convergence speed and accuracy are achieved while maintaining processing simplicity. Moving average filter (MAF), whose filter characteristics usually seen as insufficient for most applications, is an ideal structure for APF application. In APFs, the distorting signals occur at the multiple frequencies of the fundamental frequency component. If the side-lobes occurring in a MAF are adjusted to be at the harmonic frequencies then the reference signal extraction accuracy will be improved. Another advantage of A-LMS is its fast convergence. The adaptation constant, which is effective on convergence speed, cannot be chosen higher in LMS derived algorithms due to its noise increasing effect. On the other hand, in A-LMS algorithm, since the signal to noise ratio (SNR) can be kept minimum the adaptation constant can be chosen higher to increase the convergence speed. In this paper, after giving information about A-LMS structure, it is shown that A-LMS is an ideal reference signal extraction method for APF applications through simulation and practical test results.
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Keywords: APF, Averaged-LMS, Harmonic Distortion, LMS, Power Factor Correction.
Novel Ćuk-Buck MPPT Battery Charger for Standalone PV-Inverter Applications
by Ahmad H. El
Khateb, Nasrudin A. Rahim, Jeyraj Selvaraj
Vol. 7. n. 2, pp. 3749-3758
Abstract - The theme of this paper is a novel MPPT converter for battery charger. The converter combines both ćuk and buck converters topologies to extract maximum power from photovoltaic arrays while supplying a controlled constant current/voltage to the battery simultaneously. The new topology uses two control signals instead of one control signal; one for maximum power point tracking, another for battery charger control providing constant current/voltage to the battery. The Advantage of this converter is to exploit the maximum power of the PV array avoiding battery damage caused by variable MPPT voltage. As a matter of fact, the tracking voltage that tracks the maximum power is variable according to weather irradiation conditions. However, batteries need constant voltage and current for charging to avoid the damage and to extend its lifetime. Therefore, it is reliable to combine the battery charger control and the maximum power exploitation using two control signals simultaneously. The real-time implementation of the ćuk-buck converter was carried in TMS320F28335 DSP. A 4kW prototype system was built and four 12V 100Ah batteries were used. The effectiveness of the proposed converter was tested in both simulation and experiment in various operating conditions. The experiment results verified that the PV power obtained of the two control signal converter was exploited better than that of one control signal and that battery’s full charging state was reached in a relatively short time.
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Keywords:
Battery Charger, Maximum-Power-Point Tracker (MPPT), Voltage and
Current Control, Photovoltaic (PV).
Design and Implementation of an Intelligent Maximum Power Point Tracking
Controller for Photovoltaic Systems
by K. H. Chao, C.
L. Chiu
Vol. 7. n. 2, pp.
3759-3768
Abstract - The primary purpose of this study is to propose an intelligent maximum power point tracking (MPPT) method for photovoltaic systems. First, PSIM simulation software is used to build a 516 W photovoltaic (PV) module array to be used during the simulation of the proposed MPPT method. To ensure that the power output generated by the PV module array is at maximum under various conditions of irradiation, this study also proposes the use of an intelligent MPPT tracker. The proposed MPPT method is a system based on the extension theory, with the capability of executing steps involving automatic change tracking (CT) so as to quickly zero-in on the maximum power point (MPP) in the PV module array. This study first uses simulation results to verify the feasibility of the proposed MPPT method. Then, this study constructs an actual maximum power tracking circuit, and uses a programmable system-on-chip (PSoC) to realize this MPPT method. Finally, the experimental results validate that the proposed MPPT method does possess excellent dynamic response and steady state performance.
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Keywords: Maximum Power Point Tracking (MPPT) Method, PSIM Simulation Software, Extension Theory, Maximum Power Point (MPP), Programmable System-on-Chip (PSoC).
Design and Implementation of Robust Controller for PMSM Drive
by Guo-jun Tan,
Hui Zhang1, Jing Li, Zhi-xun Ma, Rui-wen Yu
Vol. 7. n. 2, pp. 3769-3778
Abstract - The paper firstly expounds the H∞ robust control theory for the permanent magnet synchronous motor (PMSM). Appropriate weighting functions are selected and the Riccati inequality is solved to derive the H∞ controller. Then, a nonlinear robust controller based on L2 gain is proposed to improve the dynamic and static performance of PMSM. The controller is designed through back-stepping method, which divides the PMSM control system into two subsystems. Furthermore, according to the dissipation inequality theory and by means of constructing the appropriate storage function, it is demonstrated that the virtual stabilization functions of the two subsystems derived from back-stepping method can meet the two design requirements for the nonlinear robust controller based on L2 gain, which means the proposed nonlinear robust controller presents an asymptotically stable characteristic when there is no external disturbance as well as attenuates the disturbance when there is. Finally, the experimental results demonstrate that the nonlinear robust controller presents stronger robustness and more satisfactory disturbance attenuation than both the conventional PI controller and H∞ robust controller.
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Keywords:
Robust Control, PMSM, H∞ Control, Nonlinear Control,
Back-Stepping Method.
Optimization
of Mover Parameters in High Thrust Density Transverse Flux Linear Motor by
Genetic Algorithm
by M. R. Zare, M.
Norhisam, Aravind C.V, N. Mariun, I. Aris, H. Wakiwaka
Vol. 7. n. 2, pp.
3779-3786
Abstract - This paper proposed the optimum dimension of Permanent Magnet (PM) and thickness ratio of mover poles to obtain maximum motor constant square density (G) in a High thrust Density Transverse Flux Linear Motor (HDTFLM) using Genetic Algorithm. The Permeance Analysis Method (PAM) is used to derive the magnetic equivalent circuit of the machine and Genetic Algorithm (GA) is used as optimization tool. The thickness ratio of the middle poles of the mover to side pole of the machine, the thickness and the height of PM are to be optimized in order to obtain the optimum structure of HDTFLM. FEM results and experimental results are used to verify the analytical method. A comparative evaluation shows that the motor constant square density of the optimized structure is 4.6 times bigger than that of the original HDTFLM structure. The motor constant square density of the optimized structure HDTFLM is 10.6 times bigger than the HDLM model.
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Keywords: High Thrust Density, Transverse Flux, Linear Motor, Genetic Algorithm, Permeance, FEM, Motor Constant, Motor Constant Square Density.
A
New Type of Three-Phase Two layers 6 by 4 Switched Reluctance Motor:
Configuration, Simulation and Experimental Results
by A. Siadatan, E.
Afjei
Vol. 7. n. 2, pp. 3787-3794
Abstract - The Switched Reluctance Motor (SRM) is a high speed; simple and robust structure motor with high output torque and no windings on its rotor. In this paper, a two-layer 6 by 4 switched reluctance motor is proposed and investigated. The motor is simulated employing 3D Finite Element Method (FEM) to realize the motor characteristics. The flux linkage and static torque profile of the motor as well as the flux density flow of the motor through the rotor, stator and shaft is extracted by the simulation results. Furthermore, the prototype of the motor is fabricated to determine the validity of the results obtaining from simulation. The experimental analysis is performed using one conventional SRM which is coupled to fabricated motor as a load. The setup provides torque-speed and torque-current characteristics of the motor the shape as well as the measurement of the motor are taken out.
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Keywords: Two Layer Switched Reluctance Motor, 3D Finite Element Method (FEM), Static Torque.
On
the Fault-Tolerance of Permanent Magnet Synchronous Machines and Drives used in
Hybrid Vehicle Application
by D. Fodorean,
D.C. Popa, M. Ruba
Vol. 7. n. 2, pp.
3795-3803
Abstract - The paper presents a study of the fault tolerance problem on three types of electrical machines and drives used in hybrid vehicles. Three types of faults and the tolerance to faults is analyzed on these machines: material damage due to lack of remanence in the permanent magnets, construction fault and the effect of losing the phases of the machine or of the legs of the inverter used to drive the machine. The study presented in this paper is evaluated numerically and experimentally.
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Keywords:
Fault-Tolerance, Permanent Magnet Machines and Drives, Hybrid
Vehicle.
Discrete Rotor Flux Estimator for High Performance Induction Motor Drives with
Low Sampling to Fundamental Frequency Ratio
by Igor R. Krčmar,
Petar R. Matić, Darko P. Marčetić
Vol. 7. n. 2, pp. 3804-3813
Abstract - This paper reveals some high rotor speed related problems of classical discrete time flux estimators for induction motor and proposes alternative solution. At very high speeds, the ratio between sampling and fundamental frequency is very low (can be less than 15) and effects the performance of all known discrete flux estimators. The paper shows that those estimators have significant flux angle error and stability issue, and that is getting worse with rotor speed increase. In this paper stability of classically used discrete estimators is analyzed. Based on that analysis, new flux estimator based on modified Tustin approximation is proposed. The paper shows that proposed estimator is stable even for ultra low sampling to fundamental frequency ratios. Its performances and usefulness are validated via analytic stability analyses and via experimental results collected from digital induction motor drive with low sampling to fundamental frequency ratio.
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Keywords: Induction Motor, Flux Estimator, Discrete Time, Tustin Approximation.
Optimum
Design of an Inside-Out Axial-Flux Permanent-Magnet Motor using Genetic
Algorithm and Finite Element Analysis
by A. Mahmoudi, S.
Kahourzade, N. A. Rahim, W. P. Hew
Vol. 7. n. 2, pp. 3814-3827
Abstract - This paper presents an inside-out axial-flux permanent-magnet brushless DC motor optimized by Finite Element Analysis (FEA) and Genetic Algorithm (GA) based sizing equation. The TORUS motor of the slotted-stator design comprises sinusoidal back-EMF waveform and maximum power density. The GA attained the dimensions which provided the motor with the highest power density. Electromagnetic field analysis of the candidate motor from GA with various dimensions was then put through FEA in order to obtain and re-optimize the motor’s characteristics. Possible design parameters were investigated by putting Commercial Vector Field Opera 14.0 software through a three-dimensional FEA simulation and using MATLAB 2010a for GA programming. Techniques like modifying winding configuration and skewing permanent magnets were investigated to attain the most-sinusoidal back-EMF waveform and reduced cogging torque. The desired technical specifications were matched according to the 3D FEA and GA simulation results. FEA and GA simulation results compared and agreed well to the flux density in different areas of the designed motor at no-load condition.
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Keywords: Axial-Flux Permanent-Magnet Motor, Finite Element Analysis, Genetic Algorithm, Sizing Equation, TORUS.
Design and Application of a Hybrid Motor with a Rotor Structure Having
Changeable Magnet and Reluctance Combination
by E. Kandemir
Beser, S. Camur, B. Arifoglu, E. Beser
Vol. 7. n. 2, pp. 3828-3835
Abstract - In this study, design and application of a hybrid motor is introduced. The rotor of the hybrid motor includes separate magnet and reluctance parts. Each part also consists of six pieces. A considerable feature of the motor is that the combination of the parts can be suitably changed due to the magnet and reluctance pieces. The mechanical angle between the parts can also be varied. Three rotor constructions as completely magnet, completely reluctance and a hybrid rotor having three magnet and three reluctance pieces were studied in this work. First, finite element analysis (FEA) were used to analyze and predict the torque behaviors of the motors. Mathematical model of the proposed motor was formed in terms of a,b,c variables considering the combination of the magnet and reluctance parts on the rotor. Simulations were performed through the mathematical equations for three motor types. The proposed motor and drive system were manufactured, and its performance was tested. Analysis and simulation results were verified by the experimental results of the static torque measurement and load tests. There is a good accordance between experimental and simulation results. The proposed hybrid motor shows a compound dc motor characteristic because of including both magnet and reluctance parts. Different load demand can be satisfied by the developed motor structure achieving different hybridization on the rotor.
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Keywords:
Hybrid Motor, Magnet, Reluctance, Hybridization, Finite Element
Analysis.
Topology
and Control Design of Sinusoidal Very Low Frequency High Voltage Generator
by Liu Zhigang,
Tang Yao, Wang Zhiqiang
Vol. 7. n. 2, pp. 3836-3844
Abstract - The topology and the control strategy of a novel sinusoidal very low frequency (VLF) high voltage generator are introduced in this paper. To minimize the influence of distributed parameter of High Frequency High Voltage transformer, Series-parallel (LCC) resonant technology is applied to reduce the impact of the distributed parameters，decreasing the power loss and the volume of the transformer. The Closed-Loop control technology is adopted to reduce the influence by the combination of changing duty cycle and operating frequency. Simultaneously, the principle of segmental data processing is proposed to obtain different steady state operating points, greatly reducing the calculation of the Microcontroller Unit (MCU), improving the control accuracy. As a result, it was accomplished by MCU successfully. The test of the 35kV/0.1Hz power supply has been taken on a capacitor (1.5uF) which is equivalent to the XLPE cable on electrical character. Total harmonic distortion is less than 1% which can meet IEEE400.2 standard well. The results of the experiment verify the accuracy and feasibility of the control theory and the topology.
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Keywords: VLF High Voltage, Sinusoidal VLF, Segmental Data Processing.
An Adaptive Robust Predictive Current Control for PMSM With Online Inductance
Identification
by Niu Li, Yang
Ming, Xu Dianguo
Vol. 7. n. 2, pp. 3845-3856
Abstract - This paper presents an adaptive robust predictive current control for permanent magnet synchronous motors (PMSM) based on deadbeat control law. The proposed algorithm calculates the switch state of the inverter against next period according to the current commands, and adopts a luenberger observer to increase the system stability. This method extends the allowance of inductance error of traditional predictive control system efficiently, and increases phase margin of the current control system as well. Based on online inductance identification, the proposed algorithm balances the stability and frequency response of the control system dynamically during the motor running. A 750W PMSM is involved to verify the performance of the proposed algorithm, and then the simulation and experiment results are analyzed.
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Keywords: Permanent Magnet Synchronous Motor, Current Control, Predictive Control, Robustness.
A Fault-Tolerant Sensorless Control Method For Switched Reluctance Motor
by Jun Cai,
Zhiquan Deng
Vol. 7. n. 2, pp. 3857-3865
Abstract - Sensorless control of Switched Reluctance Motor (SRM) drives based on phase inductance subregion is a relatively simple and obvious technique. However, its application has been reported only for choosing the suitable starting phase at standstill, and other sensorless techniques need to be combined for controlling the SRM during running conditions. In this paper, the validity of the method for sensorless control of SRM both at standstill and running condition, including phase-lacking fault mode and phase current sensor fault mode, are demonstrated. Experiments have been done for verification. The results show that this method possesses good starting and speed regulation performance, and good fault tolerant capacity under light load applications. This method does not require additional hardware, memory, and complex calculation, which is quite easy for implementation.
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Keywords: Switched Reluctance Motor, Sensorless Control, Inductance Subregion, Starting, Fault Tolerant.
Incorporation of Sliding Mode Control into Current and Direct Torque Controllers
for Induction Motor Drives
by Mehmet Dal
Vol. 7. n. 2, pp. 3866-3876
Abstract - In this paper, applications of discrete-time sliding mode control (DSMC) method to both current control and direct torque control (DTC) of induction motor (IM) drives are presented. The proposed control law is derived using Lyapunov analysis and sliding mode control methodology. The current controller parameters are determined by an analytic procedure carried out in discrete domain. The performance of the current control algorithm is simulated in field oriented control (FOC) scheme using a slow sampling time and verified by experiments conducted on high-power prototype IM drive system. Moreover, the proposed control scheme is extended to a DTC of IM and its potential is demonstrated by computer simulations. Finally, advantages and several distinct features of the proposed control method are highlighted.
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Keywords: Sliding Mode Control, Induction Motor, Medium Voltage Drive, Current Control, Direct Torque Control.
Performance Improvement of Torque Characteristics Using the Multi Type Interior
Permanent Magnet Motor
by M. Norhisam, S.
Khodijah, Nashiren F. Mailah, D. Ahmad, Aravind CV, M. R. Zare, H. Wakiwaka
Vol. 7. n. 2, pp.
3877-3884
Abstract - The torque characteristic of the novel Multi Type Interior Permanent Magnet (MTIPM) motor that can be operated as permanent magnet stepper (PMST) and dc brushless motor (BLDC) configuration is presented. It briefly presents the structural characterization and the derivation of performance characteristics of the machine from the first principles. This motor is designed as high torque performance motor that can be used in-wheel motor for agriculture application such as tractors. BLDC motors exhibit characteristics of generating high torque at high speed while the PMST has characteristic of generating high torque at low speed. The typical characteristics of the above two are integrated in the MTIPM structure with complex control structure that handle the switching complexity and speed control in real time. The evaluation of the performance characteristics of the proposed machine is presented. The result shows significant improvements of the practical torque range.
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Keywords: Multi-Type Interior Permanent Magnet Motor, High Torque Performance, Machine Design.
Comparative Electromagnetic Evaluation of Different Structures of Switched
Reluctance Motors
by H. Torkaman, E.
Afjei, N. Ghadimi, A. Gorgani
Vol. 7. n. 2, pp. 3885-3890
Abstract - This paper evaluates the performance characteristics and comparison results of four different types of switched reluctance motors. These motors have 12/10, 6/4,12/8, and 8/8(or isolated phase) configurations. The 6/4 configuration includes, a motor with one tooth per stator pole, where as in 12/10 arrangement, there are two teeth per stator pole. In 12/8 arrangement, a motor is of the cylindrical type with one tooth per stator pole and the other one is of the isolated phase geometry where each phase consist of eight rotor and stator poles. The areas of all stator pole faces jointly involving in torque production mechanism in the motors are taken to be equal. The numerical analysis gives a better understanding of the flux distribution inside the motors and can be used to compute, optimize motor performance and parameters. The terminal inductance per phase, the flux linkage of each stator pole winding, and the components of leakage inductances are determined and plotted for different rotor positions and excitation currents. Finally the static torque for different forced current levels and rotor positions are also presented for each motor.
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Keywords: Switched Reluctance Motor,Electromagnetic Analysis, Comparative Study.
Subdomain Analytical Magnetic Field Prediction of Slotted Brushless Machines
with Surface Mounted Magnets
by Akbar Rahideh,
Theodosios Korakianitis
Vol. 7. n. 2, pp. 3891-3909
Abstract - An analytical magnetic field calculation is presented for slotted brushless machines with surface mounted magnets. The magnetic field distributions due to both permanent magnets (PMs) and armature currents are predicted using the subdomain technique considering the effects of tooth-tips. The open-circuit magnetic field calculation can be used for any radius-independent magnetization pattern and in this study six different magnetization patterns have been studied: radial sinusoidal amplitude; ideal Halbach; radial; parallel; 9-segment Halbach; and 2-segment Halbach magnetization. The armature reaction field prediction is presented for both overlapping and non-overlapping winding structures and two non-overlapping winding cases with all teeth wound and alternate teeth wound are investigated. The calculations are applicable to any rotary motion radial-flux internal rotor slotted stator brushless machine equipped with surface mounted magnets with any pole and slot combination. The analytical results of the magnetic flux density for a 6-slot/4-pole brushless DC motor have been presented and compared to those obtained from the finite element method to evaluate the analytical expressions.
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Keywords: Permanent Magnet, Armature Field, Open-Circuit Field, Brushless Motor, Magnetization, Slotted, Tooth-Tip.
Evaluating the Thermal Behavior of Induction Motor under Unbalanced Voltage
by Hassan Feshki
Farahani, Abdorreza Rabiee, Mohammad Khalili, Roozbeh Kamali
Vol. 7. n. 2, pp.
3910-3915
Abstract - The operation of electric machine at higher temperature than its nominal operating point one causes to decrease the lifetime of machine. Therefore, it is critical to monitor the stator and rotor temperature to protect motor in the case of thermal overloading conditions. The winding temperature can be risen in special conditions such as motor stall, overloading, unbalanced operation and etc. In this paper, the effect of unbalanced voltage on temperature rising of motor is studied. The rotor and stator monitoring system is firstly constructed. Then different tests such as blocked rotor, no-load and etc., are performed on a typical 1.1 kW / 50 Hz/ 1400 rpm motor under different unbalanced conditions of power supply. Finally, the effect of each kind of unbalanced voltage on the motor temperature rising is investigated.
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Keywords: Voltage Unbalance Factor, Induction Motor, Thermal Monitoring, Unbalance Supplying.
An
Experimental Effort to Understand How Behaves Winding High Frequency Response in
Power Transformers
by H. Firoozi, A.
Akbari, M. I. Ghiasi
Vol. 7. n. 2, pp.
3916-3925
Abstract - Frequency Response Analysis (FRA) is a powerful technique for condition monitoring and fault diagnosing of power transformers. The challenge in this regards is the analysis of the transformer transfer functions due to different faults. In other words, the correlation between different faults and transfer functions is not fully yet known. The main idea in this study is that the transformer physical and insulating structure during manufacturing stages are changed. Therefore, investigations on the variations of winding transfer function in these stages can be very helpful. In this contribution the transformer winding is simulated in different manufacturing stages. All simulations performed for a 63/20Kv, 30MVA power transformer based on available design information. Some measurements are also performed to verify the simulation results. The obtained results are useful to understand high frequency characteristics of winding and also can be used to interpret the changes in the transfer function due to different common faults.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Transfer Function, Frequency Response Analysis (FRA), Active Part, Power Transformer, Fast Fourier Transform (FFT).
Modeling
of Partial Discharge in Transformer Winding by Multi-Conductor Transmission Line
Model
by S. M. Hassan
Hosseini, M. Vakilian, M. Ghaffarian Niasar
Vol. 7. n. 2, pp.
3926-3934
Abstract - To locate accurately the occurrence of a partial discharge in a power transformer winding, a wide frequency band model of the winding is required. In this paper a wide frequency band Multi Conductor Transmission Line model (MTL) is employed to simulate the propagation of PD signal in transformer windings. The MTL model is briefly reviewed and the related equations of the model are reformulated to easily simulate occurrence of a PD signal along the winding. Software is developed in Matlab to calculate the windings resonance frequencies and the magnitudes of over-voltages occurring between different disks along the winding. Then propagation of PD signal in a power transformer (900MVA, 525kV), is simulated using the (MTL) model with frequency dependent parameters. Also this method is employed to model the laboratory transformer winding.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Partial Discharge, Transformers, Multi-conductor Transmission Line Model.
Influence
of Simulation Precision on Broken Rotor Bars Fault Diagnosis Accuracy in
Induction Motors
by Wejdan
Abu-Elhaija, Bashir Mahdi Ebrahimi, Jawad Faiz
Vol. 7. n. 2, pp.
3935-3940
Abstract - In this paper, impacts of the modeling precision on the accuracy of broken bars fault detection in induction motors are investigated theoretically and experimentally. Hence, finite element method (FEM) and winding function method (WFM) as two powerful modeling approaches, are utilized to simulate the healthy and faulty induction motor under broken rotor bars. Then, spectrum of the stator current which is calculated using the WFM that ignores magnetic saturation, and FEM which considers the non-linear characteristics of ferromagnetic materials, is evaluated. The amplitude of side-band components at frequencies (1±2ks)fs as the most applicable and common index for broken bar fault diagnosis in induction motors are determined and compared with experimental results. Furthermore, performance of the healthy and faulty induction motor is computed using WFM and FEM and spectrum of the speed is utilized for invasive broken bar fault detection. In order to justify the obtained results, the distribution of magnetic flux density of the healthy and faulty motor at start-up and steady-state cases with and without saturation effects is analyzed.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Induction Motor, Magnetic Saturation, Broken Bar Fault Diagnosis, WFM, FEM.
Assessment
of Second Life of Lithium Iron Phosphate Based Batteries
by N. Omar, M.
Daowd, O. Hegazy, B. Geukens, J.M. Timmermans Th. Coosemans, P. Van den Bossche,
J. Van Mierlo
Vol. 7. n. 2, pp. 3941-3948
Abstract - This paper reports the possibilities of "second-life" use of lithium iron phosphate based traction batteries. The results reveal that the investigated battery cells have still considerable high potential for recovering in stationary applications such as grid energy storage, uninterruptible power supply systems as well as renewable power management systems. In the second life, the examined battery cells have achieved 1500 cycles compared to 350 cycles in the first life. The analysis reveals that the increase of the Peukert value is limited. Moreover, the experimental results illustrate that the energy efficiency of the battery cells is >80%. According to these results, the battery cells show significantly high capacity decrease during the first stage (<200 cycles). Then the capacity maintains stable, which is analogue to the battery characteristics during the first life cycle. Moreover, from 1000 cycles the battery cells capacities decrease very fast. In this study, a relative heavy load profile has been chosen to examine the battery cells performances during the second life. The battery cells have been cycled at 2 It and 80% depth of discharge.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Second Life, Lithium Iron Phosphate, Life Cycle.
Obtaining Renewable Energy from Piezoelectric Ceramics Using Sheppard-Taylor
Converter
by Ahmet
Karaarslan
Vol. 7. n. 2, pp. 3949-3956
Abstract - This paper presents a harvesting vibrational energy with piezoelectric ceramics using a single phase Sheppard-Taylor converter. In this study, the renewable energy is obtained by the piezoelectric ceramics and the converter regulates the power flow to the desired load. The control of the Sheppard-Taylor converter satisfies optimal working points using vibration-powered piezoelectric generators as a source. The circuit describes the generator’s power dependence and helps the definition of the load behavior for power optimization. The performance of the energy harvesting circuit is investigated by Matlab/Simulink program and laboratory conditions. Experimental results show that the converter controlled by a very low consumption circuit effectively maximizes the power flow into a 12 V. The rechargeable Lithium-ion battery charger connected to the converter output. The converter’s efficiency is above 80% for input voltages between 0.5 and 12.8 Vrms, and for output powers between 1.2 mW and 25 W. The presented circuit and control strategy can be used as well for power optimization of piezoelectric energy harvesting devices.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Piezoelectric Ceramic, Renewable Energy, Energy Conversion, Sheppard-Taylor Converter, Battery Charger.
Compensation of Wind Generator Power Fluctuations in Microgrid Applications by
Superconducting Magnetic Energy Storage
by Marcelo G.
Molina, Gastón O. Suvire, Pedro E. Mercado
Vol. 7. n. 2, pp. 3957-3968
Abstract - Grid connection of wind power generation (WPG) is becoming today an important form of distributed generation (DG). The penetration of these DG units into AC microgrids (MGs) is growing rapidly, enabling reaching high percentage of the installed generating capacity. However, the fluctuating and intermittent nature of this renewable generation causes variations of power flow that can bring both power quality and reliability issues to the electrical grid. To overcome these problems, superconducting magnetic energy storage (SMES) arises as a potential alternative to compensate these power flow fluctuations and thus to significantly enhance the MG dynamic security. To this aim, the management of the energy stored in the SMES device is crucial for optimizing the storage capacity as well as for preventing the device from becoming overcharged or uncharged. This paper proposes the use of an improved SMES controller for the stabilization of the fluctuating active power injected into the microgrid by wind generators. In this sense, the design and implementation of a high performance active power controller of the SMES is described. The control is based on fuzzy logic techniques and uses an enhanced fuzzy inference system (FIS) combined with a unique filter block. Moreover, a detailed model of the SMES unit and its power conditioning system (PCS) for connecting to the electric grid is derived. The dynamic performance of the proposed system and its impact on the MG operation is validated by computer simulation.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Microgrid (MG), Distributed Generation (DG), Wind Generation,
Superconducting Magnetic Energy Storage (SMES), Fuzzy Logic Controller (FLC),
Detailed Modeling.
International Review of Electrical Engineering - Papers- Part B
Underfrequency Load Shedding with Forecasting of the Power System’s Frequency
Response
by Urban Rudez,
Rafael Mihalic
Vol. 7. n. 2, pp.
3969-3978
Abstract - The importance of a secure supply with electrical energy in the world is increasing. With every problem concerning a security of supply with electrical energy, industry is faced with huge financial consequences. This is why even partial power system blackouts should be always prevented. This is possible by implementing sophisticated control and protection mechanisms. One of the most important power system protection mechanisms, which are able to prevent blackout during underfrequency conditions, is underfrequency load shedding. However, in the majority of power systems it has remained unchanged for decades, despite the advances in computer and communication technologies. To support changes in this field, a proposal for an adaptive load-shedding scheme has been developed, which is suitable from both the technical and economic points of view. By using this scheme any unnecessary load disconnections and power system blackouts are prevented. This is achieved by forecasting the response of the regulatory mechanisms that influence the system frequency by applying a locus diagram of the frequency versus the frequency’s first time derivative. The scheme has been tested on models of the IEEE 9-bus system and a part of Slovenian power system. Using both models, the presented approach shows remarkable results.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Adaptive Control, Frequency Response, Power System Islanding, Power-System Protection, Underfrequency Load Shedding.
Energy Management Strategy for a Grid–Connected Wind-Solar Hybrid System with
Battery Storage: Policy for Optimizing Conventional Energy Generation
by Rabeh Abbassi,
Souad Chebbi
Vol. 7. n. 2, pp. 3979-3990
Abstract - The aim of this paper is to develop and simulate supervisory algorithms for optimum operation of an integrated hybrid renewable energy system. The studied system is based on a DC-coupled Wind/Photovoltaic Hybrid System (WPVHS), equipped with battery storage system, which delivers on the power grid in presence of a conventional generator. The purpose of the supervisory algorithms is to control, each of the different sub-systems, individually taking account of all power exchanges performed via the DC-link and the Point of Common Coupling (PCC). This is in order to manage the total energy supply. With the above mentioned supervision algorithms, the service continuity was assured by meeting the energy demand while optimizing the conventional sources use and replacing them, except in case of major deficit, by renewable ones. Our new algorithms have been tested via MATLAB software and the obtained results demonstrate the reliability and the robustness of the proposed strategy.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Renewable Energies, Wind/Photovoltaic Hybrid System, MPPT, Common DC-Link, Back To Back Converters, SVPWM, Energy Storage, Conventional Source.
Security
Constrained Optimal Power Flow Using Artificial Bee Colony
by H. A.
Zamani, S. M. Ezzati1, H. Vahedi, M. Gandomkar
Vol. 7. n. 2, pp.
3991-3999
Abstract - This paper presents Artificial Bee Colony (ABC) for solving Security Constrained Optimal Power Flow (SCOPF). The aim is to minimize the operating total cost taking into account operating and security constraints, system capacity requirements and improve the bus voltage profile under normal or contingent states. In this paper we have used 26-bus and the IEEE 30-bus system as test systems. In addition, the results are compared with the Particle Swarm Optimization Algorithm with Reconstruction Operators (PSO-RO) and Mixed-Integer Bacterial Foraging Algorithm (MIBFA) in MATLAB.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Security Constraint Optimal Power Flow (SCOPF), Artificial Bee Colony (ABC), Dependent Variables, Control Variables.
Inter-Area
Oscillations Damping by Multi-Objective Wavelet Neural Inverse Controlled SSSC
by Soheil
Ganjefar, Mojtaba Alizadeh
Vol. 7. n. 2, pp.
4000-4012
Abstract - A Multi-Objective Wavelet Neural Adaptive Inverse Controller (MOWNAIC) for Static Synchronous Series Compensator (SSSC) is proposed in this paper. A new local structure network, referred to Self-Recurrent Wavelet Neural Network (SRWNN), is initially trained off-line over a vast range of operating conditions and disturbances with an aim to identify the inverse input-output mapping of the plant. Later on, it is placed in the control system configuration and is used so as to damp the power system oscillations. An inverse plant emulator is also employed to online handle changes in the system conditions and/or configurations, and, consequently, to increase control performance. To guarantee the convergence of the proposed control scheme, a stable Back-Propagation (BP) training algorithm with Adaptive Learning Rates (ALRs) based on discrete Lyapunov stability theorem is employed in order to on-line update all weights of the emulator. The proposed controller is applied to a SSSC in a two-machine two-area power system in order to damp the inter-area oscillations. Simulation results reveal that; the proposed controller for SSSC is more superior in the improvement of stability of the system compared to that of the conventional PI controller. Finally, the design problem is successfully extended to four-machine two-area benchmark system.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Adaptive Learning Rates (ALRs), Discrete Lyapunov stability theorem, Inverse control, Power system stability, Self-Recurrent Wavelet Neural Network (SRWNN), Static Synchronous Series Compensator (SSSC).
High
Impedance Fault Detection using Hilbert Transform and Least Square Support
Vector Machine for Distribution Feeders
by Chen Min-you,
Hu Gang, Zhai Jin-qian
Vol. 7. n. 2, pp. 4013-4020
Abstract - This paper presents a new time-frequency analysis technique based on Hilbert transform for extracting the feature of high impedance faults (HIFs) detection in electrical distribution feeders. Based on residual current of distribution feeder, energy of intrinsic mode decomposition component and standard deviation of magnitude and phase of each IMF are considered as feature inputs to the least square support vector machine (LS-SVM) classifier, thus, HIF are distinguished from low impedance faults (LIFs) and normal operation events. The results obtained have validated the effectiveness of the proposed methodology to detect HIFs and discriminate them from LIFs and normal transient operations.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: High Impedance Fault, Distribution Feeders, Hilbert Transform, Least Square Support Vector Machine.
Solution Space Optimization for Network Reconfiguration Considering Power
Distribution Network Characteristics
by Huang Yuhui,
Liu Dong, Liao Huaiqing, Yu Wenpeng,Weng Jiaming
Vol. 7. n. 2, pp. 4021-4026
Abstract - The choice of initial feasible solutions for power distribution network optimization algorithms will affects the computational efficiency. However, it may often be overlooked the impact of electrical characteristics of power grid to the initial feasible solutions. The initial feasible solutions optimal method for network reconfiguration, which considering power grid characteristics with network simplification and switch grouping by analyzing the distribution network topology based on CIM model, is presented in this paper. The solution space condition which satisfying the radial operation of distribution grid and under the inductive network reconfiguration constraints is established in this paper. A case study using genetic algorithms for distribution network reconfiguration shows that the computational efficiency of optimization algorithms will increases exponential multiple times by the proposed method of solution space optimization.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Distribution Network，CIM(Common Information Model), Topological Contraction, Solution Space Optimization.
A New Approach for DG Allocation in Distribution Network with Time Variable
Loads using Cuckoo Search
by Z. Moravej, A.
Akhlaghi
Vol. 7. n. 2, pp. 4027-4034
Abstract - DG allocation in real distribution network with time variable loads using a novel approach is presented in this paper. The daily load profile with 1-hour interval between two subsequent stages is applied for achieving the real condition. The optimization problem which is the combination of the loss and total average steady state voltage fluctuation is solved by the new approach based on cuckoo search (CS). The voltage fluctuation in each bus is measured by adding the variation of voltage between two subsequent stages. The CS which is the main purpose of this paper, has been compared with genetic algorithm (GA) and particle swarm optimization (PSO). For indicating the applicability of the proposed algorithm, different cases which have been implemented on two distribution networks considering time variable loads have been studied. The results show the better performance of CS compared with other approaches.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Distributed Generation, Cuckoo Search, Power Loss, Time Variable
Load, Voltage Fluctuation.
Hybrid
Model for Analysis of Ground Fault Current Distribution
by S. Vujević, Z.
Balaž, T. Modrić, P. Sarajčev
Vol. 7. n. 2, pp. 4035-4045
Abstract - This paper presents a hybrid numerical model for computation of the phase-to-ground fault current distribution between soil and neutral conductors of grounding system. Hybrid model is combination of electromagnetic model and transmission line model. In numerical realization, the finite element technique is used. Using electromagnetic model, conductive coupling between all buried non-insulated conductive parts of grounding system is taken into account. Using transmission line model, inductive coupling between phase conductors and ground wires of parallel overhead power lines is used. Similar transmission line approach is used for parallel power cable lines and cable line grounding wires. In computer programs developed for ground fault current distribution, the conductive coupling between all buried non-insulated conductive parts of grounding system can be taken into account or neglected. From the numerous numerical examples, it can be deduced that one can introduce a significant error by neglecting the conductive coupling. In presented numerical example, error caused by neglecting the conductive coupling between all buried non-insulated conductive parts of grounding system can be observed in rms values and phase angles of currents and potentials.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Hybrid Model, Electromagnetic Model, Transmission Line Model, Finite Element Technique, Phase-to-Ground Fault Current Distribution, Buried Non-Insulated Conductive Parts of Grounding System, Conductive Coupling, Inductive Coupling.
A
Robust Decentralized TSFPI Design as Power System Stabilizer
by A. Jalili, H.
A. Shayanfar, H. Shayeghi
Vol. 7. n. 2, pp. 4046-4054
Abstract - This paper presents a robust decentralized Power System Stabilizer (PSS) based on Takagi-Sugeno Fuzzy PI (TSFPI) technique for damping power system low frequency oscillations. This newly proposed method is simple and easy to implement. The realistic power system is composed of subsystems that interact with each other. For decentralization, this paper assumes that each subsystem includes a generator connected to the rest of the system through tie lines. In each subsystem, PSS can be designed independently based on TSFPI technique. With the newly proposed method a simple and natural procedure is developed to handle the nonlinear control system. The effectiveness of the proposed method is verified on the New England 10-machine 39 bus standard power system under various load demand and disturbances in comparison with the Strength Pareto Evolutionary Algorithm (SPEA) based PSS and Fuzzy PID (FPID) based PSS through nonlinear time domain simulations and performance indices such as ITAE, FD, ISE and ITSE. The results evaluation show that the proposed control strategy achieves good robust performance for a wide range of system parameters and load changes in the presence of system nonlinearities and is superior to the SPEA based PSS and FPID based PSS.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: PSS, TSFPI, Power System Control, Dynamic Stability.
Signal Processing of On-line PDs Captured by Rogowski Coil for Enhanced Fault
Detection in Smart Distribution Networks
by M. Hashmi, M.
Lehtonen, M. Nordman, S. Hänninen
Vol. 7. n. 2, pp. 4055-4064
Abstract - On-line partial discharge (PD) measurements can be used as a condition monitoring tool to detect falling/leaning trees on the covered-conductor (CC) overhead distribution networks. PD measurements conducted in the high voltage (HV) laboratory are less affected by electromagnetic disturbances (EMD). However, on the other hand, on-line/on-site PD measurements conducted in smart distribution networks are often affected by several disturbances. Extracting low level PD signal from noisy backgrounds is a major challenge for on-line condition monitoring. In this paper, wavelet transform (WT) technique is proposed as a powerful tool to de-noise on-line PD signals in CC overhead distribution lines, which are completely buried by electromagnetic interference (EMI). The on-line PD signals are captured in the laboratory environment and on-site PD measurements are simulated. The principle of de-noising based on multi-resolution signal decomposition (MSD) is implemented. The validation of WT technique is carried out by comparing its effectiveness with other available filtering techniques. Rogowski coil is used as a PD sensor to capture PD signals in this specific application. In the future, the proposed method will be implemented in a real-life environment to get more stable and reliable on-line/on-site PD measurement results for enhanced fault detection in smart distribution networks.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Partial Discharge, Condition Monitoring, Covered-Conductor, Smart Distribution Networks, Electromagnetic Disturbances, Wavelet Transform, Rogowski Coil.
Assessment of Transmission Loss Allocation Algorithms in Deregulated Power
System
by M. Y. Hassan,
M. A. AlMaktar, M. P. Abdullah, F. Hussin, M. S. Majid, H. A. Rahman
Vol. 7. n. 2, pp.
4065-4076
Abstract - In most of the competitive electric pool markets worldwide, transmission losses are not included in transmission use of system charge. Thus, the charge levied to transmission users is based solely on DC power flow regardless the amount of power losses the users cause in the transmission grid. This allocation of transmission losses is significant for the transmission owner as well as it could help reducing locational charge for the user creating counterflow to relieve the transmission network. This paper focuses on the analysis of the performance of different loss allocation methods for pool-based electricity market. The study is based on: pro-rata; proportional sharing; Z-bus; modified nodal equation; current adjustment factors, incremental loss (ITL) and Loss Utilization Factor (LUF) method. Case studies based on a simple 5-bus and IEEE 14-bus systems are used to show the capability of different loss allocation algorithms in allocating losses to the transmission users.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Loss Utilization Factor, Pool-based Electricity Market, Transmission Loss Allocation.
Optimal
Line Surge Arresters Installation Using Lightning Location System
by Viktor Milardić,
Ivo Uglešić, Alain Xemard
Vol. 7. n. 2, pp. 4077-4084
Abstract - The paper
presents a methodology for the reduction of the number of lightning
flashovers on a 220 kV double-circuit line. From the geometry of the
line and the ground-flash density it is possible to calculate the number
of flashovers. The procedure for the calculation of flashovers includes
three steps: application of an electro-geometric model, simulation of
the electromagnetic transients due to lightning strokes and evaluation
of the flashover rate. The models of the elements used in the
calculation are presented: lightning stroke current, tower, conductors,
insulator string, line surge arrester (LSA) and tower footing
resistance. The case study of a 220 kV double-circuit overhead line is
conducted in order to improve its lightning performance. Different
mitigation measures on a line for prevention of flashovers could be
applied and one of the most effective means is the installation of LSAs.
The best solution depends on the number of LSAs, their location and
their price. Data from Lightning location system (LLS) can also help for
the choice of towers for LSA installation. Calculations are conducted
using the software EMTP-RV and LIPS.
Copyright © 2012 Praise Worthy Prize S.r.l. -
All rights reserved
Keywords: Line Surge Arresters, Lightning Location System, 220 Kv Double-Circuit Line, Modeling, EMTP-RV, Flashover, Lightning Performance.
Consideration of Multi-state Unified Power Flow Controllers Models in
Reliability Assessment of Electric Power Systems
by Bo Hu, Kaigui
Xie, Rajesh Karki
Vol. 7. n. 2, pp. 4085-4091
Abstract - The utilization of Unified power flow controller (UPFC) can result in significant reliability benefits in modern power systems. This paper proposes a novel reliability network model for a UPFC, which incorporates the logical structure and the distinct operating modes of a UPFC. The proposed model divides the UPFC operating modes into seven states, in order to improve the accuracy of the model by recognizing the practical operating states of a UPFC. The new model also incorporates an AC flow-based optimal load shedding approach to assess the impact of bus voltages and reactive power flow on UPFC in order to decide appropriate load curtailment in the reliability evaluation process. The performance of the proposed model is verified using a test system. Various operating schemes, such as different placement locations of UPFC, and different capacities of UPFC are used to examine the impacts of UPFC on the system reliability.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords:
Unified Power Flow Controllers, Reliability, Power System, AC
Flow-Based Optimal Load Shedding Approach.
Solving
Optimal Capacitor Placement Problem Using Improved Bi-Strategy Differential
Evolutionary Algorithm Considering Varying Load Conditions
by H. Shayeghi, M.
Karimi, P. Farhadi
Vol. 7. n. 2, pp. 4092-4104
Abstract - In this paper, an Improved Bi-Strategy Differential Evolutionary (IBSDE) algorithm has used to find optimal location and size of capacitor banks in radial distribution network. The IBSDE has been obtained by applying several improvements on original Differential Evolutionary (DE) algorithm. These improvements have been done on mutation operator and adding migration to escape from local optima point. To solve Optimal Capacitor Placement (OCP) problem, objective function has been formulated as a maximum annual cost saving. In addition to cost, three main parameters have been considered as decision criteria; i.e. active power loss, minimum voltage of network and total capacitor instillation. In this study, three load levels have been regarded as; i.e. constant, varying and effective loads. The Proposed BSIDE has been carried out on two standard and a realistic distribution networks test systems. The standard systems are IEEE 10-bus and 34-bus radial distribution systems and actual system is 73-bus Kian-Pars region of Ahvaz city in south of Iran. To demonstrate the effectiveness as well as reliability of the proposed algorithm, obtained results is compared with the other recently represented method results and original DE algorithm. Finally, two statistical indexes i.e. absolute percentage error and symmetric mean absolute percentage error is introduced to illustrate robust performance of the proposed IBSDE algorithm for the solution of the OCP problem that of other recently reported methods.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Optimal Capacitor Placement, Bi-Strategy Differential Evolutionary Algorithm, Variable and Effective Loads, statistical Analysis.
Genetic
Algorithm Tuned Optimal Variable Structure System Controller for Enhanced Load
Frequency Control
by K. R. M.
Vijaya Chandrakala, S. Balamurugan, K. Sankaranarayanan
Vol. 7. n. 2, pp.
4105-4112
Abstract - In this paper, the Load Frequency Control (LFC) is enhanced with optimal gains of the Variable Structure System (VSS) Controller tuned using Genetic Algorithm (GA). For analysis, two-area thermal and hydrothermal power plants are considered in this paper. Conventionally, Proportional Integral Derivative (PID) controller is used to control frequency and tie-line power deviations. To improve the PID control action during transient and steady state period, the PID controller is replaced by VSS Controller. The gains of the controllers are tuned using Zeigler Nichols’ (ZN) and further with GA optimization technique. The performance of the controller is judged using Integral Time Absolute Error (ITAE) method. On analysis, it is observed that frequency and tie-line power deviations are improved using GA tuned VSS controller.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Load Frequency Control, Proportional Integral Derivative Controller, Variable Structure System Controller, Genetic Algorithm, Hydrothermal Power Plant.
Effect of Customer Demand Type on Optimization of Distributed Generation for
Minimization of Energy Loss
by R. Ebrahimi, M.
Ehsan, H. Nouri
Vol. 7. n. 2, pp. 4113-4122
Abstract - The problem of distributed generation (DG) optimization in distribution systems has normally been assessed by assuming a constant power (real and reactive) load model. Such assumptions may lead to inconsistent and misleading results about loss reduction, DG optimization and other subsequent calculations. In this paper, the effect of different types of demand, e.g. industrial, residential and commercial, and its time varying effects on distribution networks is investigated. Customer demand type is defined by the load model that is voltage dependent and the load patterns from real life hourly demand data. The study shows that by defining the energy loss minimization as the objective function, the type of customer demand significantly affects the optimal location and sizing of DG resources in distribution networks, whereas consideration of power loss as the objective function leads to inconsistent interpretation of loss reduction, voltage profile, total power intake of system and other calculations. A comparative study on 9 and 17-bus networks for different customer demand types is also shown for various cases and scenarios and results are discussed in this paper.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Distributed Generation, Distribution Networks, Energy Losses, Customer Demand Type, Genetic Algorithm (GA).
Multi-machine Power Transmission System Stabilization Using MPSO Based
Neuro-Fuzzy Hybrid Controller for STATCOM/BESS
by Stella Morris,
Morris A. G. Ezra, Yun Seng Lim
Vol. 7. n. 2, pp. 4123-4133
Abstract - This
paper deals with the design of a new hybrid controller for damping the
electromechanical oscillations in a multimachine power transmission
system. The new controller is designed for a VSI-based STATCOM (Static
Synchronous Compensator) with a battery energy storage system (BESS). A
combination of real power flow deviation, STATCOM bus voltage deviation
and dc link voltage deviation is fed to the proposed hybrid controller
which generates the control signals. The proposed hybrid controller uses
a two-layer neuro-fuzzy PI control model which is a function based
Takagi-Sugeno-Kang fuzzy scheme. In order to avoid repeated computation
of the controller parameters at different operating conditions, a
modified particle swarm optimization (MPSO) technique is used to adapt
the parameters. To demonstrate the application of the proposed
controller, a number of case studies are carried out in two
multi-machine power transmission systems with STATCOM/BESS installed at
one of the buses. The efficacy of the proposed controller is evaluated
by a digital computer simulation using MATLAB under various transient
disturbances and a wide range of operating conditions.
Results are presented to verify the feasibility and practicality of the
proposed ideas. Investigations reveal that the transient performance of
the power system is remarkably improved with the incorporation of BESS
and the proposed hybrid controller.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: STATCOM, BESS, Modified PSO, Neuro-Fuzzy, Hybrid Controller.
Localization of Multiple Harmonic Sources in Non-Radial Power Distribution
Systems
by Masoud
Farhoodnea, Azah Mohamed, Hussain Shareef, Hadi Zayandehroodi
Vol. 7. n. 2, pp. 4134-4145
Abstract - This paper represents a new method for identifying the locations of multiple harmonic sources in power systems using independent component analysis and mutual information theory. Independent component analysis, which is a blind source separation technique, is applied for estimating the profiles of injected harmonic currents produced by harmonic sources. The mutual information theory has been applied for determining the exact location of harmonic sources. Numerical simulations were made to verify the accuracy of the proposed method in locating multiple harmonic sources in the test distribution systems. Results showed that the proposed method can accurately estimate the location of multiple harmonic sources without using the knowledge of many network parameters.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Harmonic Distortion; Harmonic Source Location; Multiple Harmonic Sources; Power Quality.
Heuristic
Optimization based-Fixed Structure Robust H∞ Loop Shaping Controller
Design with Automatic Weights Selection of Controllable Distributed Generations
for Microgrid Stabilization
by Sitthidet
Vachirasricirikul, Issarachai Ngamroo
Vol. 7. n. 2, pp. 4146-4154
Abstract - In the microgrid with wind and solar power generations, the power fluctuation from such intermittent sources is an inevitable problem. To handle such situation, the distributed generations (DG) with controllable power i.e., electrolyzer (ES) and microturbine (MT) can be applied. This paper proposes a heuristic optimization based-fixed structure robust H∞ loop shaping controller design with automatic weights selection of controllable DGs for microgrid stabilization. To guarantee the system robust stability margin, the normalized coprime factorization is applied to represent unstructured uncertainties. The proportional integral (PI) is selected as the controller structure of ES and MT. For comparison purpose, the particle swarm optimization (PSO) and genetic algorithm (GA) are applied to optimize the PI parameters based on the H∞ loop shaping design. Simulation results show that the PSO-based control design is superior to GA-based controller design in terms of computation efficiency, robustness against system uncertainties and stabilizing effect.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: H∞ Loop Shaping Control, Normalized Coprime Factorization, Distributed Generations, Microgrid, Heuristic Optimization, Particle Swarm Optimization, Genetic Algorithm.
A New Approach of Under-Frequency Load Shedding Technique in an Islanded
Distribution Network
by M. Karimi, H.
Mohamad, H. Mokhlis, A. H. A. Bakar
Vol. 7. n. 2, pp. 4155-4162
Abstract - Under-frequency load shedding is a common technique to maintain the power system stability by removing the overload in some part of the system. The existing under-frequency load shedding schemes operate successfully in the interconnected grid system. A particular approach of under-frequency load shedding scheme is required for an islanded system which is known to be not as strong as the grid. This paper presents a new approach of load shedding scheme in an islanded distribution system incorporating distribution state estimation. The scheme is based on an intelligent technique to reduce the effect of power deficiency in an islanded network. The disturbance magnitude is calculated based on rate of change of frequency by using the simplest expression of the generator swing equation. Moreover, the process for assessing the power consumption of the customer can be achieved by state estimation method. In this paper, state estimation for a distribution network is developed and enhanced by composite load model to obtain the most practical value of the system state variables. Finally, the calculated value of the disturbance magnitude will be shed according to the estimated value of loads in each bus.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Distribution State Estimation, Under-frequency Load Shedding, Distribution Network, Distributed Generation, Islanding.
Performance Comparison of Voltage Sag Source Detection Methods for Power Quality
Diagnosis
by A. Mohamed, H.
Shareef, M. F. Faisal
Vol. 7. n. 2, pp. 4163-4171
Abstract - Voltage sag is considered as a major power quality problem that can disrupt the operation of sensitive equipment. Many power utilities around the world install power quality recorders at strategic sites to monitor the frequency and severity of voltage sags that may affect their customers. The identification of sources of voltage sags is also critical for determining the causes of the disturbances. The source of sag can either originate from upstream or downstream with respect to the monitoring point. This paper presents a comparative study to investigate the performance of the various voltage sag source detection methods, namely, the Voltage-Current, Disturbance Power, Incremental Impedance, Directional Relay, Real Current Component and S-transform Disturbance Power methods. The results showed that the STDP method is superior in detecting symmetrical and asymmetrical voltage sag sources in industrial power systems compared to the other compared methods.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Power Quality, Time Frequency Analysis, Sources of Voltage Sags, S-Transform.
Application of a New Combined Technique to Power Quality Events Classification
by Z. Moravej, M.
Pazoki
Vol. 7. n. 2, pp.
4172-4182
Abstract - This work proposes an effective scheme for automated Power Quality (PQ) events classification by using new combined Slantlet Transform and Multi Support Vector Machine (ST-MSVM). The recognition of PQ events is a very important task for finding the cause of equipment malfunction. Since PQ disturbances are non-stationary signals, the ST is an improvement of the Discrete Wavelet Transform (DWT) which can be applied effectively as feature extraction method. In order to increase the generalization capability of classifier, correlated features are removed by Pearson’s correlation method. The extracted features are given as an input to MSVM system for classification procedure. Various PQ events as well as simultaneous events are tested by the proposed ST-MSVM method. The results show the proposed algorithm can detect and classify different PQ signals correctly, even under noisy conditions, with high accuracy. Data generation for classifier testing is done by parametric equation and simulation software. The signals generated in these ways are very similar to reality, moreover noisy condition which is very close to the real situation also has been considered.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Power Quality, Feature Extraction, Multi Support Vector Machine (MSVM), Slantlet Transform (ST).
Optimal Placement and Sizing of Static Synchronous Compensators in Power Systems
Using Improved Harmony Search Algorithm
by Reza Sirjani,
Azah Mohamed, Hussain Shareef
Vol. 7. n. 2, pp. 4183-4193
Abstract - In this paper, a relatively new optimisation technique, the improved harmony search algorithm (IHS), is used to determine the optimal location and size of static synchronous compensators (STATCOMs) in a transmission network. The problem is decomposed into two sub-problems. The first sub-problem is the optimal placement of STATCOM devices using the modal analysis method. The second sub-problem is the optimisation of the load flow by setting STATCOM parameters using the improved harmony search algorithm. A multi-criterion objective function is defined to enhance the voltage stability, improve the voltage profile and minimise power loss while considering the total STATCOM size. The results from a 57-bus test system show that the IHS algorithm produces a lower power loss , better voltage profile and greater voltage stability than the traditional harmony search algorithm and particle swarm optimisation techniques in solving the STATCOM placement and sizing problem.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Static Synchronous Compensator, Power Loss, Modal Analysis, Voltage Profile, Harmony Search Algorithm.
A
Performance Comparison of D-STATCOM and DC Distribution System for Unbalanced
Load Compensation
by Reza Noroozian
Vol. 7. n. 2, pp. 4194-4207
Abstract - This paper proposes a developed control strategy for a three-leg voltage source converter (VSC) in AC and DC distribution system. Also the performance of both D-STATCOM and DC distribution system have been determined and compared in the unbalanced loading conditions. First, the unbalanced loading condition has been analyzed by using developed d - q - 0 rotating frame based on symmetrical components. Second, the developed control strategy has been proposed the reference current generating for D-STATCOM in compensating unbalanced load. Third, this paper describes a DC distribution system which has been supplied by external AC systems as well as local DGs (Distributed Generations) in order to demonstrate an overall solution to unbalanced loading conditions. The power flow control in DC distribution system has been achieved by network converters. This paper proposes a developed d - q - 0 rotating frame based on symmetrical components control strategy for these converters which has a DC voltage droop regulator. In the paper, detailed simulation using PSCAD/EMTDC software has been presented to validate the developed control strategy for compensating unbalanced loading conditions. Also the performance of a DC distribution system is found to be superior to a D-STATCOM.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: VSC, Unbalanced Loading, Compensation Algorithm and DC Distribution System.
Feature Analysis of Power Quality Disturbance in Smart Grid Using S- Transform
and TT-Transform
by Chun-Yao Lee,
Yi-Xing Shen
Vol. 7. n. 2, pp. 4208-4220
Abstract - A high level of power quality is required to avoid equipment malfunction and a smart grid might be a solution to avoid the problems. The paper proposes simple rules to classify various power quality disturbances (PQDs) through illustrating characteristics of the disturbances based on feature analysis of S-transform (ST) and TT-transform (TT). In the feature analysis, the six types of time-characteristic curves (TCCs) and the five types of frequency-characteristic curves (FCCs) are depicted from the ST and TT contours of the PQD waveforms, in which the each specific characteristic can be obviously revealed by the contours in time and frequency. Finally, a manner with seven rules is generalized from the specific characteristics in this paper and can be simply used to classify PQDs. Since the classified PQDs can be obtained by the proposed manner, the amalgamation of PQDs waveforms with small size data should be useful in smart grid applications.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Power Quality Disturbance, Disturbance Classification, S-Transform, TT-Transform.
Mechanism Analysis of Voltage Quality Deterioration for Grid-Connected Photovoltaic System and Improvement Strategy
by Dong Liu, Yi You, Huaiqing Liao, Yuhui Huang
Vol. 7. n. 2, pp.4221-4225
Abstract - Nowadays, not only independent Photovoltaic (PV) system but also large-scale grid-connected PV system (GCPVS) have been widely used, due to the advantages of clean and renewable solar energy. However, the intermittence of solar energy could significantly affect the power quality of distribution network with the implementation of large-scale GCPVS. This paper focuses on the mechanism analysis of voltage quality deterioration for GCPVS and the corresponding voltage quality improvement measurements. The mathematical model of GCPVS, including PV Array, inverter devices, filtering circuit and the distribution network with GCPVS interconnected are discussed in detail. Based on the analysis of the inverter control mode of GCPVS, the mechanism that equivalent load impedance characteristic of GCPVS resulting in voltage quality deterioration superimposition effect has been exposed. Voltage sag in Point of Common Coupling (PCC) will lead to the change of equivalent load impedance of GCPVS, accordingly deteriorating voltage quality in PCC further. Additionally, some effective measurements are put forward to improve voltage quality caused by the mechanism aforementioned.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Grid-Connected Photovoltaic System, Power Quality, Mechanism Analysis, Voltage Quality Deterioration, Equivalent Load Impedance.
Optimal
Sizing of DGs in MicroGrid Considering Loss of Power Supply Probability
Technology Solved by Artificial Bee Colony
by S. M. Ezzati,
H. A. Zamani, S. M. M. Tafreshi
Vol. 7. n. 2, pp. 4226-4235
Abstract - In this paper, a methodology to execute the best unit sizing for Distributed Energy Resources (DER) in MicroGird (MG), has been improved. Based on Artificial Bee Colony (ABC) a renovated optimal unit sizing technique was improved to estimate the optimum system formation that can obtain the customers needed Loss of Power Supply Probability (LPSP) with a minimum Cost of Energy (COE). The suggested method consequences are confirmed for single source DG and hybrid DG with results obtained from HOMER and Genetic Algorithm (GA) for the similar test systems.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Optimal Unit Sizing, Cost of Energy, Hybrid Renewable Energy System, Artificial Bee Colony, MicroGrid.
Micro-Grid
Optimization as Grid - Connected inPool-Based Power Market under Pay-as-Bid and
Uniform Pricing
by
M. Mohammadi, M. Nafar, H. Nasiraghdam, B. Azadbakht
Vol. 7. n. 2, pp. 4236-4248
Abstract - This paper presents optimal operation of hybrid fuel cell/diesel generator/battery as known "Micro-grid" in pool market under various power pricing strategies such as uniform pricing and pay ad bid pricing. The present paper focuses on the comparison of two different strategy rules applied in a centralized wholesale power market: uniform pricing and pay-as-bid. The market consists of an Independent System Operator (ISO) and Dispersed Energy Resources as DER in Micro-grid (MG) and Main Utility Grid (UG) as Power Generators (Players) who submit their offers to the ISO in the form of curves. The ISO purchases energy from the Independent Power Producers (IPPs) in order to cover the electricity demand. The power producers do not know the costs, the offers and the payoffs of their competitors and therefore they use an adaptive learning tool to compensate their lack of knowledge trying to maximize their revenue. The effect of the power pricing strategy on electricity price, in a environment of market consisting of power producers with similar attributes, i.e. cost, capacity range, adaptation and reaction capability, is analyzed for both two pricing strategy systems. This paper presents a multi-objective formulation for optimal sizing of micro grid (MG) in distribution systems, under two strategy of pool power market in order to maximize net present worth (NPW). The implemented technique is based on Genetic Algorithm (GA) and weight method that employed to obtain the best compromise between these costs. Simulation performed on test distribution system to demonstrate the effectiveness of the proposed procedure.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Micro-Grid, Distribution Generation, Electricity Market, Pool Market, Pay as Bid, Uniform Pricing.
Optimal
Complex Economic Load Dispatch Solution using Particle Swarm Optimization with
Time Varying Acceleration Coefficient
by O.
Abedinia, N. Amjady, K. Kiani
Vol. 7. n. 2, pp.
4249-4256
Abstract - The objective of the Economic Dispatch Problems (EDPs) of electric power generation is to schedule the committed generating units outputs so as to meet the required load demand at minimum operating cost while satisfying all units and system equality and inequality constraints.This article presents an efficient approach for solving economic load dispatch (ELD) problems in different test power systems using Particle Swarm Optimization with Time Varying Acceleration Coefficient (PSOTVAC). Accordingly, for practical operation, many realistic constraints as; ramp rate limits, generation limitation, prohibited operating zone, transmission loss and nonlinear cost functions are considered. Test results on the modified 6, 15 and 40 unit generating system indicate that ELD solutions by PSOTVAC can give less total generation costs than Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Hybrid GA and PSO (GA/PSO), Iteration PSO (IPSO) and Self Organizing Hierarchical PSO (SOH_PSO) methods.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: PSOTVAC, Ramp Rate Limits, Prohibited Operating Zone, ELD.
A
Novel Scheme for Dynamic Network Expansion Planning in Deregulated Power System
by M.
AmirAhmadi, A. Akbari Foroud, A. A. Abdoos
Vol. 7. n. 2, pp.
4257-4270
Abstract - Network expansion planning is one of the most important parts of power system planning. Network planning in deregulated power system is more complicated than before due to new challenges and expectations in the competitive electricity markets. Deregulation of power system has introduced new objectives and requirements for transmission expansion planning. In this paper a new market based algorithm is proposed for dynamic network expansion planning in deregulated power systems. Investment cost, operation cost, average load curtailment cost in contingencies (reliability criterion) and congestion cost are considered as four objective functions in electricity market. By reducing above mentioned criteria the network reliability, operational flexibility and market competition are improved with minimum cost. To overcome the difficulties in solving the non-convex and mixed integer nature of the optimization problem, a Genetic Binary Particle Swarm Optimizer (GBPSO) is used. To consider the imprecision goals of the objectives, the fuzzy satisfying method has been applied here to select the preferred solution among the solution space. The planning methodology has been demonstrated on the IEEE 30-bus test system to show the feasibility and capabilities of the proposed algorithm in electricity market environment.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Dynamic Network Expansion Planning (DTEP), Power Market, Genetic Binary Particle Swarm Optimization, Fuzzy Satisfying Method.
Risk
Invoked Emission Constrained Self-Scheduling of a Genco: A Multi Objective
Approach
by M. Ramesh Babu,
P. Somasundaram
Vol. 7. n. 2, pp. 4271-4282
Abstract - This paper addresses a novel method for the risk invoked multi objective self scheduling (RIMOSS) of the price taking Genco in the day-ahead energy and spinning reserve market by considering conflicting objectives of the maximization of profit and the minimization of emission impacts. An elitist evolutionary multi objective optimization algorithm called Improved Non-dominated Sorting Genetic Algorithm II (INSGA-II) with controlled elitism and a dynamic crowding distance is used to solve RIMOSS. To validate the proposed method, a single generator system in the PJM market and an IEEE 30-bus test system with six generators are considered. The effectiveness of the proposed approach is demonstrated by comparing the Pareto front with a reference Pareto front generated with multiple runs of the Cauchy Mutated Particle Swarm Optimization (CMPSO) algorithm with respect to minimum spacing, diversity and convergence metric performance measures.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Cauchy Mutated Particle Swarm Optimization, Energy Market, Emission Constraint, Improved Non Dominated Sorting Genetic Algorithm II, Risk Analysis, Self-Scheduling, Spinning Reserve.
Feasible Solution Constraint-Handling Genetic Algorithm to Power Economic
Dispatch
by Felix Calderon,
Claudio Ruben Fuerte-Esquivel, Juan J. Flores, Juan Carlos Silva-Chavez, Juan
Carlos Seck-Tuoh-Mora
Vol. 7. n. 2, pp.
4283-4291
Abstract - This paper presents a new constraint-handling genetic approach based on preserving feasibility of solutions of the economic dispatch problem. A real-coded genetic algorithm is implemented to minimize the active power generation cost while satisfying both power balance and generating limit constraints automatically during the optimization process. This is achieved by introducing a novel strategy which generates solutions within the hyperspace bounded by the problem constraints, such that individuals are only produced on the feasible part of the search space that fulfill all constraints. Computer simulations on two benchmark electrical power systems show the prowess of the proposed approach whose results are similar to those reported by other authors using different methods.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Power Economic Dispatch, Genetic Algorithms, Constraint Handling Methods and Prohibited Operating Zone.
Economic Load Dispatch Solution Using Improved Time Variant MOPSO Algorithm
Considering Generator Constraints
by H. Shayeghi, A.
Ghasemi
Vol. 7. n. 2, pp. 4292-4303
Abstract - In this paper, an improved time variant Multi-Objective Particle Swarm Optimization (MOPSO) algorithm is proposed to find the feasible optimal solution of the Economic Load Dispatch (ELD) problem with considering operational constraints of the generators. For practical generator operation, many nonlinear constraints of the generator, such as ramp rate limits, prohibited operating zone, generation limits, transmission line loss and non-smooth cost functions are all considered using the proposed method. Time Variant MOPSO (TV-MOPSO) uses a new adaptive strategy to change its vital parameters i.e.: inertia weight and acceleration coefficients with iterations. This adaptiveness guides the particles to efficiently explore the search space process in algorithm within a reasonable computation effort. In addition, it preserves the diversity of Pareto optimality by a crowding entropy diversity measure tactic. The crowding entropy strategy is able to measure the crowding degree of the solutions more accurately and efficiently. For this reason, TV-MOPSO algorithm is used for the solution of ELD problem in order to efficiently control the local search and convergence to the global optimum solution. To solve ELD problem by the proposed method it is converted to a nonlinear multi-objective optimization problem with competing and non-commensurable objectives of fuel cost and transmission losses. Effectiveness of the proposed method is investigated on three different systems, including 6, 15 and 40 units generating in comparison with the performance of the other recently reported optimization techniques in the literature in terms of the solution superiority and computation efficacy.The results analysis reveals that the proposed multi objective method is effective and achieves good ability to find optimal solution for ELD problems over the other existing approaches and improves significantly the solutions quality of the power systems.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Economic Load Dispatch, Multiobjective Optimization, Time Variant MOPSO, Nondominated Solutions.
Optimal Sizing of Micro Grid & Distributed Generation Units as Standalone and
Grid-Connected under Pool Electricity Market
by M. Mohammadi,
H. Nasiraghdam M. Nafar, B. Azadbakht
Vol. 7. n. 2, pp. 4304-4313
Abstract - This paper presents a multi-objective formulation for optimal sizing of renewable energy resources in distribution systems in order to maximize net present worth of system. The implemented technique is based on Genetic Algorithm (GA) and weight method that employed to obtain the best compromise between these costs. This study presents an optimized design of Micro Grid (MG) in a distribution system including various sources like, photovoltaic array, wind turbine and battery bank for standalone mode and with multiple DG units under pool electricity market in grid-connected mode. An objective function to maximize of total net present worth is presented. The optimization algorithm is applied to a typical LV network operating under pool market policy.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Optimization, Micro-Grid, Distribution Generation, Electricity Market, Standalone.
A New Structure for Implementation of an FPGA based Overcurrent Relay
by H. Iman-Eini,
M. Sanaye-Pasand
Vol. 7. n. 2, pp. 4314-4320
Abstract - In recent years, with growing up microelectronic technology, the application of Filed Programmable Gate Array (FPGA) has been increased in industrial applications. In this paper, a new structure is proposed for an overcurrent relay which is based on FPGA technology. The new circuit can estimate the phase and amplitude of the electric signals in a very short time, even if the estimation environment is noisy or it includes harmonic components. In the proposed structure, an FPGA chip will perform the arithmetic calculations and a simple microcontroller will handle the remaining tasks. More flexibility and reliability, lower development costs, and faster time-to-market design capability are some advantages of the design. The accuracy and reliability of the proposed circuit is also verified by simulation and computer programming.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Overcurrent Relay, Digital Protection, FPGA.
Lightning
Critical Flashover Voltage of High Voltage Insulators: Laboratory Measurements
and Calculations
by Dalibor
Filipović-Grčić, Božidar Filipović-Grčić, Ivo Uglešić
Vol. 7. n. 2, pp.
4321-4328
Abstract - This paper presents the method for calculation of lightning critical flashover voltage (CFO) of high voltage insulators. Flashover occurrence on overhead transmission line insulators for 110 kV, 220 kV and 400 kV networks was studied using the leader progression model (LPM). Calculation results were compared to laboratory measurements and it was verified that presented method predicts CFO with good accuracy.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Lightning Critical Flashover Voltage, Leader Progression Model, High Voltage Insulators, Laboratory Measurements, Genetic Algorithm.
Dynamic
Pattern Recognition Approach for Partial Discharge Signature Analysis Using
Hidden Markov Models: A Critique Based on Experimental Investigations
by S.
Venkatesh, S. Gopal, K. Kannan
Vol. 7. n. 2, pp.
4329-4342
Abstract - Minor defects in insulation system of power apparatus such as cracks, inclusions, protrusions etc are unavoidable leading to partial discharges (PD). Since recognition of PD sources is essential for diagnosis and as multiple sources are encountered during real-time measurements, an array of techniques such as Neural Networks (NN), Wavelet Transformation etc have been attempted by researchers for classifying single and partially overlapped PD sources with moderate success. Since PD is a complex non-Markovian process displaying statistical variations among correlated patterns, Hidden Markov Model (HMM) serves as a viable tool in recognizing spatio-temporal and dynamically varying signatures. Hence a non-stationary continuous density HMM (CDHMM) which expresses the hidden state transition probabilities as time-dependant estimates with multivariate Gaussian densities is implemented. A novel hybrid non-stationary CDHMM-Probabilistic Neural Network recognition system is developed which utilizes the complementary advantages of HMM for identification of pattern sequences and NN for discrimination. Exhaustive studies are carried out on benchmark models and industrial objects to determine the efficacy of the hybrid system in comparison with its stationary counterpart. The focus of the research is on analyzing the role of the optimal state transition sequence of the non-stationary version in capturing the dynamic characteristic of PD patterns.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Partial Discharge (PD), Hidden Markov Model (HMM), Continuous Density Hidden Markov Model (CDHMM), Neural Network (NN), Probabilistic Neural Network (PNN).
Calculation of the Physical Characteristics of Development Streamer at Arc Head
along the Polluted Surface
by Fusheng Guo,
Wenxia Sima, Qing Yang, Tao Yuan
Vol. 7. n. 2, pp. 4343-4350
Abstract - Based on a comparison of the temperatures of electron collision with and without an insulation surface in air under an electric field, the insulation surface effect on the air discharge and the inception voltage of a continuous arc along the surface were investigated. Based on the body force of streamer and the Maxwell boundary condition, the physical characteristics of streamer radius, length, and velocity that varied with the streamer current, as well as the temperature at the arc head, were calculated. The increment velocity of temperature with an insulation surface is 100 times faster than that in the air gap, which is in favor of streamer propagation. With the increment of current and temperature, the radius, and length of the streamer all increase at different degrees. In addition, the streamer velocity along the surface is 10 times faster than that in the air gap between two parallel plate electrodes, which is at the order of 106 m/s.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Pollution, Arc, Streamer Propagation, Ionization, Surface Flashover.
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