Latest issue

International Review of
Electrical Engineering
(IREE)
December 2012 (Vol. 7 N. 6)

Part A - Part B

Cascaded Multilevel Inverter for Stand Alone PV System with Maximum Power Point Tracking Technique

by R. Kavitha, Rani Thottungal

Vol. 7. n. 6, pp. 5939-5943

Abstract - Solar energy has proven to be the most efficient source of renewable energy as it requires lesser maintenance and causes no pollution. Photo Voltaic (PV) inverter is used to convert the DC power from the PV modules into AC power to interface it to the load .The traditional inverter used in the PV system has the drawback of increased harmonic content and electromagnetic interference. Further the photo voltaic generator exhibits non linear VI characteristics and thus it is necessary to track the maximum power point. To overcome the above challenges in the PV energy conversion system a novel technique is proposed using the cascaded H-bridgeDC link multilevel inverter with maximum power point tracking system .This system is able to synthesize an improved AC voltage waveform with reduced harmonic content. The Incremental conductance technique is employed to track the maximum power of the solar cell under varying sun radiance conditions. A five level cascaded H-bridge inverter with solar panel and the MPPT algorithm is simulated using MATLAB SIMULINK. The experimental prototype is developed to investigate the performance of the MPPT controller and the Cascaded H Bridge Multilevel inverter. The proposed PV system minimizes the shading effect and increases the energy harvest.

Keywords: Cascaded H Bridge Multilevel Inverter, MPPT, Incremental Conductance Algorithm, Unipolar PWM.

Resonant Soft-Switching Noninverting Buck-Boost Converter

by M. Jabbari, M. Shahbazi

Vol. 7. n. 6, pp. 5944-5950

Abstract - A new resonant non-inverting buck-boost converter is presented. The proposed hybrid topology is formed by merging a series-resonant converter (SRC) and a SEPIC converter. The LC tank of SRC in conjunction with the inductor of SEPIC constitutes a high-frequency resonant LCL tank. Comparing with the conventional PWM SEPIC, the proposed topology includes only one additional switch. Independent from the load-current and operating voltages, soft-switching conditions are provided for both switches at turn-on and turn-off switching instants. The ZCS turn-off condition provided for the rectifying diode obviates its reverse-recovery problem. The converter can operate at DCM and CCM depend on the switching frequency. Experimental results of a 250W laboratory prototype verify operation and the presented theoretical analysis of the proposed converter.

Keywords: Non-Inverting Buck-Boost Converter, Series-Resonant Converter, SEPIC, Soft-Switching, ZCS.

Power Factor Correction Controller Design of Inductive Loads Using Magnetic Energy Recovery Switch

by Bo Long, Young Won Chang, Yongqiang Chen, Kil To Chong

Vol. 7. n. 6, pp. 5951-5960

Abstract - The following paper investigates the applications of magnetic energy recovery switch (MERS) on inductive loads. Power circuit and operation principles of MERS will be illustrated in detail. The relationship between the trigger angle in phase shift control and the MERS ratio capacitance to load inductance will be provided. Power factor correction (PFC) based proportional and integral (PI) controller for MERS have been designed. Numerical simulation and experimental results show that the proposed controller could offer better performance and lower current total harmonic distortion (THD) than the phase shift control method.

Keywords: Magnetic Energy Recovery Switch, Phase Shift Control, Power Factor Correction.

ZVT-ZCT PWM DC-DC Boost Converter with ZVS-ZCS Auxiliary Circuit

by N. Coruh, S. Urgun, T. Erfidan, S. Ozturk

Vol. 7. n. 6, pp. 5961-5969

Abstract - This paper presents a ZVT–ZCT active snubber cell for high frequency operation of dc/dc boost converter. Active snubber cell ensures zero crossings at any time required for soft switching (SS) and provides zero voltage transition (ZVT) turn-on and zero current transition (ZCT) turn-off together for the main switch of boost converter. The proposed circuit overcomes most of drawbacks of the circuits presented previously by using only one auxiliary switch with fewer other components. Moreover, all semiconductor devices in this converter operate under soft switching conditions for the whole line and load ranges. The main switch is subjected to no additional voltage and current stresses, and the stress on the auxiliary switch is very low in the proposed new snubber cell. The converter can operate at high frequencies with minimized switching losses. The proposed snubber cell is simpler and cheaper than most of the ZVT and ZCT converters presented previously and can be easily applied to the other basic converter topologies. Consequently, ZVT–ZCT DC/DC boost converter, which is verified by a prototype of a 0.35 kW and 100 kHz circuit, is analyzed in detail.

Keywords: PWM Converter, Soft Switching, Zero Current Transition, Zero Voltage Transition.

A New Switching Method, Inverted SPWM for THD, TDD and Interharmonic Reduction in VSC-HVDC

by P. Yazdanpanah Qarae, S. Gh. Seifossadat, M. Razaz, M. Joorabian

Vol. 7. n. 6, pp. 5970-5976

Abstract - This paper addresses the application of a new strategy in pulse wide modulation (PWM) technique called inverted-sine PWM (ISPWM). This technique can be used to control voltage source converters (VSC) in the light HVDC transmission systems. In this strategy, the proposed switching technique uses a sinusoidal reference signal and an inverted-sine as a carrier signal. The ISPWM technique generates lower voltage total harmonic distortion (THD) in comparison with conventional sinusoidal PWM (SPWM) technique. The new modulation technique has been studied on power transmission, THD of output voltage, TDD of current injected to load and utility network and the number of interharmonic components in output voltage and current injected from VSC to the utility network. A detailed study of the proposed modulation technique is carried out through MATLAB /SIMULINK. Simulation results show the effectiveness of the ISPWM technique to reducing of THD, TDD, interharmonic and increase the power transferred from VSC-HVDC to the power utility.

Keywords: ISPWM, THD, TDD, Harmonic and Interharmonic, VSC-HVDC Converter, Power Transferred.

A Novel Simplified Algorithm of Three-level SVPWM to the Neutral-Point Voltage Balance for NPC Inverter

by Bo Fan, Jiexin Pu, Weigang Zhao

Vol. 7. n. 6, pp. 5977-5981

Abstract - Since the disadvantages of a lot of calculation for the traditional SVPWM algorithm in the three-level neutral-point -clamped (NPC) inverter，which is not easy to real-time control，a space vector PWM (SVPWM) algorithm based on 60°coordinate system is proposed. The space vector coordinates is combined by a simple coordinate transformation, and the basic vectors are achieved by the reference vector coordinate upward and rounded down respectively, whose effective time is calculated by the principle of Volt-seconds balance. The switching state equation is introduced to control the neutral-point voltage balance and the appropriate degrees of freedom are chosen. Because of the simplified SVPWM algorithm requires no judgment of sectors and avoids the complex trigonometric equations for real-time control of three-level inverter, the results of experiment show that this algorithm has less calculation amount than the traditional algorithm，and reduces the rotation of the motor pulse.

Keywords: Neutral Point Clamped, Three-level Inverter, Space Vector Pulse-width Modulation, Neutral-point Voltage Balance.

Development of EEFL Lighting Ballast Based on Isolated Asymmetrical Half-Bridge LCC Resonant Inverter

by K. I. Hwu, Jenn-Jong Shieh

Vol. 7. n. 6, pp. 5982-5992

Abstract - In this paper, an isolated asymmetrical half-bridge LCC resonant inverter is presented, which is the kernel of the proposed lighting ballast that is used to drive an external electrode fluorescent lamp (EEFL). This lighting ballast contains three power stages if dimming is necessary; otherwise it contains two power stages only. The first power stage is constructed by a traditional boost converter with power factor correction (PFC), and such a converter operates in the critical mode (CRM). The second power stage is built up by a buck converter is used to control the duty cycle such that the corresponding output voltage can be changed and hence dimming of the EEFL can be achieved. The third power stage is established by an isolated asymmetrical half-bridge LCC resonant inverter operating under a fixed switching frequency with a fixed duty cycle. Via LCC resonance, not only the power switches of this inverter work in zero voltage switching (ZVS) so as to reduce the switching loss, but also the voltage gain is larger than one such that the turns ratio of transformer can be reduced. Most importantly, as the EEFL operates on the rated conditions, i.e., without dimming, the second power stage is to be bypassed, thereby causing the corresponding efficiency to be upgraded. The basic operating principles and corresponding mathematical deductions of the proposed inverter are described, and applied to the constructed EEFL lighting ballast that is verified by some experimental results.

Keywords: EEFL Lighting Ballast, Isolated Asymmetrical Half-Bridge LCC Resonant Inverter.

Modeling and Direct Power Control of Energy Recovery Power Battery Testing System Under Charging Mode - A New Approach

by Bo Long, To Chong Kil

Vol. 7. n. 6, pp. 5993-6004

Abstract - This paper describes the modeling and control of energy recovery power battery testing system (PBTS) under charging mode, which was usually found in evaluating the performance of power battery used in electric vehicles. First, modeling of three-phase voltage source rectifier with step-down isolation transformer interface is put forward. An outer dc-link voltage loop combined with inner feed-forward power decoupling control loop PWM rectifier scheme is proposed, then, modeling of a non-isolating DC-DC buck chopper for charging test experiment is provided. Finally, combination of the two power circuit model as a wide range battery charging testing system is investigated. Simulation and experimental results are presented to support the theoretical analysis and to demonstrate the system performance.

Keywords: DC-DC Buck Chopper, Energy Recovery, Power Battery Testing System, PWM Rectifier.

High Frequency Power Generation Using Cycloinverter with SVM

by Preeti Agarwal, Anshul Agarwal, Vineeta Agarwal

Vol. 7. n. 6, pp. 6005-6013

Abstract - Continuous need for an increased power density leads to a growing demand for high speed motors. Due to the quasi linear relation between rotational speed and shaft power of an electrical machine, increasing the rated speed is an effective way to boost power density and efficiency. Thus, high speed motor elements contribute partly to the ongoing development of green energy applications. This paper proposes high frequency power generation using cyclo-inverter with field programmable gate array (FPGA) based controller. Trigger pulses for the cycloinverter are generated using Hardware Description Language VHDL. Space vector modulation (SVM) technique, usually applied for inverters and matrix converters is modified for applying it in cycloinverter so as to obtain an output with reduced harmonic distortion. The software package MATLAB (Simulink) is used to determine the harmonics in the output and to calculate total harmonic distortion factor (THD). Lowest THD has been achieved to be 4.068 % when output frequency of cycloinverter is varied from 50 Hz to 1 MHz. Simulated results are validated experimentally using a low-cost Xilinx Spartan-3E FPGA kit. The trigger circuit is tested qualitatively by observing various waveforms on oscilloscope. The experimental results are found in close agreement to the simulated results.

Keywords: Cycloinverter, Space Vector Pulse Width Modulation (SVPWM) Technique, Field-Programmable Gate Array (FPGA).

A New Control Strategy for Three-Phase PWM Boost-Rectifier

by M. Kesler

Vol. 7. n. 6, pp. 6014-6019

Abstract - This paper presents a new control strategy for 3-phase PWM boost rectifiers that has the step-up characteristics of output DC-link voltage. The boost rectifier draws sinusoidal AC current from the AC line with active filtering and a unity power factor. In this study, the dynamics and steady-state operation of the PWM rectifier are analyzed; computer simulations and experimental results are used to validate the operating features of the proposed control strategy. Both simulations and experimental results show that the proposed control method operates successfully. As shown in the results, the proposed control strategy provides good dynamic response underDC-link load variation, and so the stability of the PWM rectifier control is enhanced. As a result, the proposed method is very effective and successful in harmonic compensation.

Keywords: AC-DC Converters, PWM Rectifier, VSI, Inverter, 3-Phase Rectifiers.

State of the Art of Control Techniques for Direct-Drive Linear Motion Systems with Tubular Linear Permanent-Magnet Motors

by Ioana-Cornelia Vese, Fabrizio Marignetti, Mircea M. Radulescu

Vol. 7. n. 6, pp. 6020-6025

Abstract - The paper compares control strategies for tubular linear permanent-magnet motors with the aim of assessing their performances in terms of dynamic performances and accuracy. The well known attractiveness of this motor is represented by its use in servo applications, with high speed and especially high precision positioning systems. The paper focuses on control techniques for direct-drive systems using tubular linear permanent-magnet motors, providing a review of electronic supply and control techniques. Finally, a Direct Thrust-Force Control strategy for a two-phase tubular linear permanent-magnet motor prototype is introduced, discussing electric supply, inverter topologies, applicability. Implementation of control techniques in dSPACE-based Hardware-in-the-Loop simulators for the embodied Direct Thrust-Force Control strategy in real time direct-drive systems confirms its applicability, highlighting the most important features of operation.

Keywords: Direct-Drives, Tubular Linear PM Motor, Direct Thrust-Force Control, Hardware in the Loop Simulation.

A RBF Neural Network Based Sensorless Control Scheme for Switched Reluctance Motor

by Jun Cai, Zhiquan Deng

Vol. 7. n. 6, pp. 6026-6034

Abstract - A new sensorless control method for Switched Reluctance Motor (SRM) is proposed in this paper. To simplify the measuring procedure and enhance the accuracy of the flux linkage, a new flux linkage calculation method is developed by combing the three-dimensional Finite element method and the measurement of the aligned flux-linkage. The Radial Basis Function (RBF) neural network is utilized for modeling the nonlinear flux linkage characteristics, and a 5-order polynomial fitting model is developed for modeling the flux/current characteristics at the turn-OFF angle. Thus, using the Turn-on angle, Turn-OFF angle and the phase current, the flux-linkage thresholds at the Turn-ON angle of the next driving phase and the Turn-OFF angle of the current driving phase can be estimated. By comparing the estimated flux linkage with the Turn-ON and Turn-OFF flux linkage thresholds, the driving signals of each phase can be estimated, which can be used for rotor speed estimation and sensorless control. Experiments verify the validity of the sensorless scheme.

Keywords: Switched Reluctance Motor, Sensorless, RBF Neural Network, Flux Linkage Thresholds.

FPGA Implementation of Neural Learning Algorithm Based MRAS Rotor Resistance Estimator Using Reactive Power for Vector Controlled Induction Motor Drive

by M. Nandhini Gayathri, S. Himavthi, R. Sankaran

Vol. 7. n. 6, pp. 6035-6044

Abstract - This paper deals with a detailed analysis and FPGA implementation of the Neural Learning Algorithm based MRAS Rotor Resistance Estimator to enhance the performance of the Vector Controlled Induction Motor drive. Variation of Induction Motor parameter causes detuning which is undesirable in high performance drives. Among all the parameters the rotor resistance of the Induction Motor is of paramount importance as they vary with temperature, frequency and skew effects and also the exact value of rotor resistance is required for the unit vector generation and slip calculation in an Indirect Field Oriented Control Scheme. The MRAS scheme using reactive power as a functional candidate for rotor resistance estimation makes the MRAS computationally simpler and easy to implement. The performance of the estimator, torque and flux responses of the drive together with the estimator is investigated with the help of MATLAB simulation for variations in the rotor resistance from their nominal value. The rotor resistance is estimated experimentally, using the neural learning algorithm based MRAS rotor resistance estimator which is implemented in FPGA. Simulation and Experimental results have been presented to confirm the effectiveness of the technique.

Keywords: MRAS, Reactive Power, Neural Learning Algorithm, FPGA, Indirect Field Oriented Control.

Experimentally Validated Current and Speed Sensors FDI Based on an Adaptive Observer for PMSM Drives

by F. Grouz, L. Sbita, M. Boussak

Vol. 7. n. 6, pp. 6045-6054

Abstract - This paper deals with a new method current and speed sensors faults detection isolation (FDI) and identification for Permanent Magnet Synchronous Motor (PMSM) drives. A new state variable is introduced so that an augmented system can be constructed to treat PMSM sensor faults as actuator faults. This method uses the PMSM model and a bank of adaptive observers to generate residuals. The residual results are used for sensor fault detection. A logic algorithm is built in such a way to isolate and identify the faulty sensor for a stator phase current fault after detecting the fault occurrence. The validity of the proposed FDI method is verified by experimental tests with 1.1-kW PMSM. The experimental implementation is carried out on powerful dSpace DS1103 controller board based on the DSP TMS320F240.

Keywords: Permanent Magnet Synchronous Motor (PMSM), Adaptive Observers, Current and Speed Sensors, Fault Detection, Isolation and Identification, Digital Signal Processor (DSP).

Design Trend of a Novel Three-Phase Five Layers Switched Reluctance Motor for High Torque Applications

by A. Siadatan, E. Afjei, H. Torkaman

Vol. 7. n. 6, pp. 6055-6061

Abstract - This paper presents a novel three-phase five layers Switched Reluctance Motor (FLSRM) with its design trend and numerical verification. The proposed motor has five 4 by 4 magnetically independent layers. By turning on each two layers and repeating the excitation schematic, the motor will produce torque. The presented FLSRM is then compared with a conventional 6 by 4 SRM with the same volume and area. The motor is designed in such a way that two layers are turned on each time, which produces more torque and also decreases the torque ripple in compare with the 6/4 SRM. The FLSRM can works in higher speed, since independent layer there is no isolation problem which exists in the conventional 6/4 SRM. On the other hand, there is more area for coil wrapping in FLSRM which means the motor can produce more torque and also the motor cooling can be done easily. The design verification is carried out by the 3-D magneto-static Finite Element Analysis to analysis the motor parameters.

Keywords: Switched Reluctance Motor, Multi-Layer Machines, High torque Applications.

A New Method for Inter-Coil Short Circuit Detection in Synchronous Machine Armature Winding

by Ante Elez, Stjepan Car, Zlatko Maljković

Vol. 7. n. 6, pp. 6062-6069

Abstract - This paper deals with detection of inter-coil short circuits in the synchronous machine armature winding, for the machines having the armature winding with coils, based on the analysis of the machines magnetic field. Applying FEM (finite element method) [4] to the generator model, magnetic field wave forms in the machine have been calculated for every point of interest, under correct and faulty conditions. Selection of the stated points has been planned with the intention to reach a correspondence of the points of interest for flux density among the calculated points and points accessible for measuring with Hall sensors in the actual machine. Comparison of results shows changes in magnetic fields in the machine caused by analyzed faults. The results of calculations are confirmed by measurements on a real machine that is altered in a way that it is possible to simulate inter-coil short circuits of one or more coil turns of the armature winding. The aim of this study is creation of a contribution to the knowledge portfolio pertaining to detection of rotation machines failures and faults, or, in other words development and improvement of monitoring systems in charge of monitoring and fault detections of rotation machines.

Keywords: Synchronous Generator, Flux Density, Hall Sensor, Generator Diagnostics.

Development of a Self-Excited Linear Induction Generator for Free-Piston Generator

by Behrooz Rezaeealam

Vol. 7. n. 6, pp. 6070-6076

Abstract - A short stroke Self-Excited Linear Induction Generator (SELIG) is constructed and its performance is predicted and compared with the experimental results. Self-excitation process, steady-state operation and stable operation region are analyzed. The effect of stroke length variation is discussed and the characteristics of the proposed generator are presented.

Keywords: Self-Excitation, Linear Induction Generator, Free-Piston Generator.

Magnetic Modeling and Comprehensive Analysis of a Novel Seven-Layer Switched Reluctance Motor for High Torque per Volume Applications

by A. Siadatan, E. Afjei, H. Torkaman

Vol. 7. n. 6, pp. 6077-6083

Abstract - The aim of this paper is to analysis comprehensively a new seven-layer switched reluctance motor (SLSRM) as an appropriate prototype to produce high torque per volume with minimum leakage flux in various applications. The SLSRM consists of seven magnetically independent stator sets, which each set includes a collection of 4 by4 stator/rotor poles. In this SLSRM, the three sets are excited simultaneously for producing high torque and also decrease the torque ripple in comparison with the single layer SRM. Additionally, this structure glories to other benefits, such as isolated phases, high speed operation, simpler cooling, and etc. To assess the suggested structure, design methodology and its configuration are proposed firstly, and the main characteristics such as flux density, flux linkage, self-inductance, mutual inductance and output torque are evaluated numerically via three dimensional finite element method (3D-FEM). The practical results show that this motor can help users to produce higher output torque per volume, with minimum leakage flux.

Keywords: Multilayer Machines, High Torque Motor, Switched Reluctance Motor, Finite Element Analysis.

Real-Time HIL-Simulation for Testing of Electric Motor Drives Emulating Hydraulic Systems

by Jani E. Heikkinen,Tatiana A. Minav, Juha J. Pyrhönen, Heikki M. Handroos

Vol. 7. n. 6, pp. 6084-6092

Abstract - Verification of an electro-hydraulic system of a working machine is carried out by hardware in loop (HIL) simulation using multi-body-dynamics-based software by MeVea Oy as a real time simulator of the mechanical parts and electrical drives as hardware-in-loop components. Comparing analysis and verification of the HIL model with practical results are also performed for an axial piston hydraulic machine drive. The purpose is to demonstrate the possibility to test the drive with hydraulic load which was emulated by an electric drive. This enables one to construct different system identification, parameter estimation, control tuning and state monitoring algorithms based on testing in real time simulation environment. Recommendations for improving the HIL-setup were created.

Keywords: Drives, Pumps, Permanent Magnet Machines, Energy Efficiency, Energy Recovery Model, Hardware In Loop (HIL), Real-Time Simulation.

Transformer Winding Fault Classification Based on Pattern Recognition Technique

by Sanjay Agrawal, A. K. Chandel, S. R. Mohanty, Vineeta Agrawal

Vol. 7. n. 6, pp. 6093-6103

Abstract - Recognition of transformer winding fault conditions by analyzing the current waveform disturbances is very important task for transformer health monitoring. This paper presents a novel approach for classification of transformer winding fault conditions viz. ageing, arcing and inter-turn short circuit at different loads, which is based on discrete wavelet transform (DWT), Parseval’s theorem and neural network. In the proposed technique DWT is used to decompose signals into different resolution levels and then energies of these levels are calculated to determine powerful features. Further, useful feature information is used to develop neural network classifier. The effectiveness of neural network classifier is verified by giving unknown winding fault inputs and comparing the results with known outputs. Results thus obtained show the versatility of the classifier in classifying the winding faults of transformers.

Keywords: Ageing, Arcing, Classification, Inter-Turn Short Circuit, Multi-Resolution Analysis, Parseval’s Theorem.

Design of Transformer-less High Power Output Battery Testing System Using Three-Level NPC Inverter

by Bo Long, DaeyeongLim, Kil To Chong

Vol. 7. n. 6, pp. 6104-6115

Abstract - The main objective of the present work is to extend three-level neutral point clamped (NPC) voltage source converter (VSC) in the application of medium voltage and high power output energy recovery power battery testing system (ERPBTS). Current decoupling scheme based proportional-integral control scheme combined with space vector pulse width modulation (SVPWM), is firstly illustrated to integrate discharging energy to the power grid. Active and reactive power references for the grid-connected inverter are decided according to the discharging energy in dc-dc converter, which could keep the dc-link voltage constant at the same time. The synthesized control scheme for the composited power circuit which is composed of three-level NPC VSC and boost chopper is put forward. It is shown that the proposed scheme could offer less total harmonic distortion and higher dc-bus voltage utilization than that of the conventional power circuit in ERPBTS. The proposed method is implemented and verified both by simulation and experimental results in an IGBT-based ERPBTS using embedded DSP controller.

Keywords: Energy Recovery, Power Battery Testing System, Three-Level Neutral Point Clamped Inverter.

Motor Ballbearing Outer Race Fault Detection Using Wavelet Packet Decomposition, an Experimental and Simulation Study

by R. Kianinezhad, P. Mirjani, S. Gh. Seifossadat

Vol. 7. n. 6, pp. 6116-6122

Abstract - Many researches has been done for motor ballbearing fault detection via stator current analysis and several signal processing method has been proposed for this purpose during recent years. Among different mathematical transforms, wavelet transform has shown to be a powerful tool for non stationary signal processing (Induction motor current signal is a non stationary signal). This research focuses on wavelet packet decomposition of stator current which has been applied for bearing fault detection and the effectiveness of the proposed method has been verified by simulation and experimental results compared to conventional spectral analysis method.

Keywords: Bearing Fault Detection, Wavelet Packet Decomposition, Non Stationary Signal, Induction Motors.

Inductor Saturation Detection with Anti-Saturation Control Strategy Taken Into Account

by K. I. Hwu, Jenn-Jong Shieh

Vol. 7. n. 6, pp. 6123-6128

Abstract - In this paper, detection of inductor saturation, together with anti-saturation control, is presented, which is applied to a synchronously-rectified (SR) buck converter. Since the inductor maybe sometimes work in a saturation situation, such as overload. In theory, as the inductor is saturated, the corresponding current slope in the inductor will be increased, and such a phenomenon can be used to judge whether the inductor is saturated or not. However, as this phenomenon occurs, variations in current are not easy to obtain because of limitations of slope detection speed and effects of noise interruption. Therefore, the detection of the inductor current ripple amplitude and the load current, together with the input voltage information, is used to judge whether the inductor is saturated or not. Afterwards, once the inductor is saturated, the proposed anti-saturation control strategy is applied to make the inductor work far from saturation. In this paper, some experimental results are provided to verify the proposed detection and compensation of inductor saturation.

Keywords: Inductor Saturation Detection, Anti-Saturation Control .

Part A - Part B

A Non Linear MPPT Control of Photovoltaic Pumping System Based on Discrete Sliding Mode

by Br. Khiari, A. Sellami, R. Andoulsi, A. Mami

Vol. 7. n. 6, pp. 6129-6136

Abstract - In this paper we propose a control strategy of a buck converter coupling a Photovoltaic generator to a DC motor pump for tracking the maximum power. The proposed strategy is based on the discrete sliding mode control theory of nonlinear systems. This work is motivated by the need to use the maximal power of PV generator; witch is a special source of finished energy that has a non-linear current-voltage characteristic dependent on temperature and solar illumination. The input reference of the regulation loop is given by a maximum power point research algorithm and the tracking of this reference is made using the discrete sliding mode control, the stability as well as the choice of sliding surface is addressed. Some reliable simulation results are provided in the following paper in order to demonstrate the efficiency of the proposed approach and then experimentally validated.

Keywords: Photovoltaic (PV), Maximum Power Point Tracking (MPPT), Buck converter, Discrete Sliding Mode Control (DSMC).

Optimal Sizing of Power Sources and Energy Management for Positive Energy Buildings

by Mario González, Ghaith Warkozek, Vincent Debusschere, Seddik Bacha, Salim Haddad

Vol. 7. n. 6, pp. 6137-6144

Abstract - A method for the optimal sizing of energy sources and for the optimal plan of energy management of a positive energy building is presented in this paper. The method, based on linear programming, allows determining the optimal area of a PV installation, the optimal battery installation size, and the minimum power to be contracted with the electricity provider. This optimal sizing allows obtaining the return of the investment costs of the installation and allows obtaining gains from selling the exceeding electricity produced locally. In addition, a proposed optimal plan for energy management permits attaining a positive energy net flux from the power flow in the grid on a daily/monthly/annually average basis and thus leading to economical gains from the locally produced electricity sales.

Keywords: Energy Management, Optimal Sizing, Positive Energy Building, Renewable Energy.

AbSDE Algorithm: a Novel Approach to Solve Multistage Optimal Substation Placement

by M. Karimi, P. Farhadi, M. Fard, M. Anwari

Vol. 7. n. 6, pp. 6145-6152

Abstract - In this paper, a novel structure has been suggested for Deferential Evolutionary (DE) Algorithm to find optimal size/location of substation. To improve simple DE algorithm, four improvement stages are applied on DE algorithm which is called Adaptive bi Scenario Deferential Evolutionary (AbSDE) algorithm. In improvement process, at first, crossover rate and scaling factor of mutation operator are adapted. Then two scenarios are introduced for mutation operator and finally migration operator is added to DE algorithm to escape from local optimal points. The AbSDEA has been used to solve a multistage Optimal Substation Placement (OSP). The OSP is formulated in three stages; the number and size/location of substation are obtained at first and second stages, respectively. In third stage, cost of project formulated as function of geographical and electrical parameters. Simulation is done in six load levels and two novel indices are defined to analyze obtained results from proposed algorithm. To confirm capability of AbSDE algorithm to solve OSP problem, results of the algorithm have been compared with simple DE and Particle Swarm Optimization (PSO) algorithms.

Keywords: Distribution System Planning, Differential Evolutionary Algorithm, Optimal Substation Placement.

Study on Non-Contact Transmission Line Overvoltage Sensor and Analysis of Influencing Factors

by Yong Yang, Licheng Li, Lin Du, Afei Chang

Vol. 7. n. 6, pp. 6153-6160

Abstract - This paper develops a non-contact overvoltage sensor to capture overvoltage signals of overhead transmission lines, presents the basic principle of overvoltage sensor, and analyzes the line-board model of the sensor. Employing the series–parallel method, the stray capacitance was calculated, and the result was proven by simulation in Ansoft Maxwell. This work designs the structure of the sensor. By conducting frequency and lightning impulse-voltage experiments, the performance and measurement accuracy of the sensor was verified. In this paper, various factors that influence the sensor were analyzed. The corona theory points out that corona influences the capacitance of the high-voltage arm of the sensor. The impulse-voltage experiment proved that the impulse-voltage time is too short to have little influence on the sensor. Experiments on the influence of temperature, humidity, and pollution were conducted. The results proved that the effect of atmosphere on the sensor can be ignored. The tower will have an effect on the sensor. The experiment showed that the influence of the tower is stable, and the influence on the divider ratio can be excluded in the sensor calibration. This paper proposes a non-contact overvoltage sensor, which is simple and easy to implement.

Keywords: Non-Contact Overhead Voltage Sensor, Overhead Transmission Line, Lightning Voltage, Influence Factors.

A Modified Seeker Optimization Based Economic Dispatch of Generators with Valve-Point Effects and Multiple Fuel Options

by R. Sharma, P. K. Rout

Vol. 7. n. 6, pp. 6161-6170

Abstract - This paper presents a novel and efficient optimization approach based on modified seeker optimization (MSO) technique for solving the economic dispatch (ED) problem with smooth and non-smooth cost functions. The conventional approaches often fail to find the global optimum due to increase in complexity of the problem while considering the practical operational constraints like ramp rate limit, prohibited operating zones and the valve point loading of the thermal generators. The proposed Modified Seeker Optimization (MSO) approach employs a narrowing step-length strategy to improve its exploitative nature, as the search proceeds. The variable step-length makes the algorithm explorative in nature initially and later makes the local search capability more aggressive. To show the efficiency and effectiveness, the proposed MSO is applied to different types of ED problems with smooth and non-smooth fuel cost functions. Firstly, four test systems consisting of 6, 15, 40 and 110 generating units with ramp rate limits, prohibited operating zones and valve-point loading effects are considered separately. Secondly, a test system of 10 units is taken with multiple fuels. The experimental results show that the proposed MSO approach gives better solutions when compared with previous approaches.

Keywords: Modified Seeker Optimization, Non-Smooth Cost Functions, Economic Load Dispatch, Prohibited Operating Zones, Valve-Point Effects, Ramp Rate Limits.

Stability Control of Wide-Area Power System with Multiple Time Delays

by Gulizhati Hailati, Jie Wang

Vol. 7. n. 6, pp. 6171-6181

Abstract - The stability of wide-area power system with multiple time delays is investigated in this paper. A new steady stability analysis model of power system with multiple time delays is constructed. Based on the proposed model, the delay fractioning based on Lyapunov-Krasovskii approach is used to derive a delay-dependent steady stability criterion to obtain the two level of damping controller for the power systems. The damping controller is divided into two parts: The first level of control is derived from local signals without time delays, and it satisfies the requires that the real part of all eigenvalues of state matrix of system is negative; The second level of control is supplied by a coordinator using global states with different multiple time delays. The criteria of stability are formulated as feasibility problems of linear matrix inequality (LMI). The maximal delays and parameters of the damping controller which allow the closed-loop power system to retain stable, are calculated based on the LMI technique. Finally, the relationship between the delay fractioning of the criteria and the damping controller is discussed. Taking a two-area four-machine power system as an example, the performance of the proposed controller is verified by the results of simulation in time-domain, and it is proved that the method proposed in this paper is effective.

Keywords: Wide-Area Measurement System (WAMS), Time Delays, Linear Matrix Inequality (LMI), Damping Controller, Delay Fractioning.

Improvement of Dynamic Response of AGC System Using Thyristor Controlled Phase Shifter and Optimization of System Parameters

by B. Bakhshideh Zad, H. Hasanvand, J. Lobry, H. Maskani, B. Mozafari

Vol. 7. n. 6, pp. 6182-6189

Abstract - This paper presents the analysis of different two-area automatic generation control (AGC) systems in presence of thyristor controlled phase shifter (TCPS) and aims to improve the dynamic response of the proposed AGC systems in terms of minimizing system oscillations. In this study, TCPS unit is used to change the relative phase angle between the system voltages; as a result, regulate the real power flow to mitigate the frequency oscillations. Also, the values of integral controller gain of each area as well as the gain constant of TCPS unit are optimized with implementing improved particle swarm optimization (IPSO) method and gravitational search algorithm (GSA). The results reported in this paper demonstrate that the oscillations of frequency in both areas and tie line power oscillations can be effectively damped out by the use of TCPS unit that is located in the tie line. Furthermore, it can be concluded that the positive impact of using TCPS on the dynamic response of AGC system strictly depends on the dynamic response of generator, turbine and governor of the system. Among the three studied cases, positive impact of using TCPS in hydro-hydro system which has more oscillatory nature is much better than that of thermal-thermal or thermal-hydro system. Moreover, comparative studies of GSA and IPSO techniques confirm the high performance and effectiveness of both proposed methods in finding the optimal values of the studied systems.

Keywords: Automatic Generation Control, Thyristor Controlled Phase Shifter, Improved Particle Swarm Algorithm, Gravitational Search Algorithm.

Nonlinear Coordinated Control of HVDC and TCSC for Damping Inter-Area Oscillations of Parallel AC/DC Power System

by Fang Shi, Jie Wang

Vol. 7. n. 6, pp. 6190-6196

Abstract - The low frequency oscillation problem of the inter-connected power grid will limit the transmission capacity even lead to instability of the power system. Some series connected devices, such as HVDC and TCSC, can be directly used to suppress the energy oscillations in the transmission lines. As the emerging of the parallel AC/DC interconnected power systems, this paper present a coordinated controller of the HVDC and TCSC to damp the inter-area oscillations. Firstly, the equivalent structure and mathematical model is illustrated and represented as generalized Hamilton structure, which is characterized with the oscillation energy of the power system as the Hamiltonian function. Furthermore, the coordinated control strategy, which has a physical meaning of energy balance and damping injection, is designed via Lyapunov stability theory and proven to be effective. Lastly, a parameterized equivalent power system is taken as an example to test the controller and the experimental results demonstrate the effectiveness of the methodology presented in this paper.

Keywords: AC/DC Parallel Power System, Coordinated Control, Oscillation Energy, Generalized Hamiltonian Function.

Smart Energy Management System for a Microgrid by Considering Uncertainties

by Reza Roofegari Nejad, Seyed Masoud Moghaddas Tafreshi

Vol. 7. n. 6, pp. 6197-6208

Abstract - Nowadays the rapid growth for using renewable energy resources and determination of energy price by energy market have created new uncertainties for power systems operation. In this paper, a novel model for optimum operation of a microgrid which connects to the upstream distribution network (UDN) and consists of dispatchable and nondispatchable supplier, energy storage system and controllable and uncontrollable loads has been proposed. In this model microgrid’s manager can control demand of controllable loads according to the technical and economical requirements of itself. In order to modeling uncertainties of renewable generation, energy price, demand power of loads, and also the failure probability of units or UDN, Monte Carlo simulation method has been used. According to this method at first, various scenarios for the possibility of uncertain factors have been extracted and reduced by scenario reduction method then all of these scenarios with other required inputs have been applied to the operation optimization program. For this optimization program, an objective function from the microgrid’s manager’s point of view has been extracted and then maximized. In order to better realization, the proposed method has been implemented on a typical microgrid and the simulation results of proposed operation planning and deterministic planning has been compared.

Keywords: Smart Energy Management System, Microgrid, Monte Carlo simulation method, Controllable loads, Operation Uncertainties.

The Using of Curve Fitting Prediction Optimized by Genetic Algorithms for Short-Term Load Forecasting

by M. A. Farahat, M. Talaat

Vol. 7. n. 6, pp. 6209-6215

Abstract - This paper presents a new approach for short-term load forecasting. Curve fitting prediction and time series models are used for hourly loads forecasting of the week days. The curve fitting prediction technique combined with genetic algorithms is used for obtaining the optimum parameters of Gaussian model to obtain a minimum error between actual and forecasted load. A new technique for selecting the training vectors is introduced. The proposed model is simple, fast, and accurate. It is shown that the proposed approach provide very accurate hourly load forecast. Also it is shown that the proposed method can provide more accurate results. The mean percent relative error of the model is less than 1 %.

Keywords: Load Forecasting, Curve Fitting Prediction, Genetic Algorithms, Short-Term.

Meta-Heuristic Algorithms Based Active Power Loss Minimisations

by Attia El-Fergany, Mahdi El-Arini

Vol. 7. n. 6, pp. 6216-6224

Abstract - This manuscript presents integrated evolutionary approaches to minimise the real power losses in a given power-system network to improve the system performance and to reduce the overall cost of power transmission. The integration of the Genetic Algorithm and hybridised Simulated Annealing with Pattern Search are proposed and applied to determine the optimum adjustments to the control variables. The approach satisfies and maintains the equality and inequality constraints. The proposed method is applied to many test systems with different operating scenarios. The numerical test results and simulations with different load patterns and single line outages were demonstrated and analysed. The effects of changing the control variables were studied and investigated as well. The results obtained show the effectiveness, flexibility, and applicability of the proposed integrated approaches for power loss minimisations by considering the overload condition of lines with high accuracy and within somehow an acceptable computational time.

Keywords: Active Power Loss Minimization, Control Variables, Line Overloading, Meta-Heuristic Based Algorithms.

Multi-Objective Optimization of a Microgrid Considering Load and Wind Generation Uncertainties

by Guiting Xue, Yan Zhang, Yujiao Liu

Vol. 7. n. 6, pp. 6225-6234

Abstract - This paper builds a multi-objective optimization model based on chance constrained programming (CCP) for microgrid (MG) operation. The model aims to minimize the economic costs, carbon emissions, and node voltage deviations by optimizing the outputs of controllable distributed generators (CDGs). Considering the uncertainties related to load and wind speed, deterministic constraints on node voltages and branch transfer powers are inaccurate, thus they are expressed as chance constraints. Cumulant-based probabilistic load flow (PLF) method is used to check the probability constraints. Clonal selection algorithm (CSA) is applied to solve the optimization model, and a fuzzy-based decision maker is employed to select the ‘best’ compromised solution among the calculated Pareto-optimal solutions. Simulation results on a 33-node hypothetical radial MG analyze the relationship between economics and confidence levels and discuss the impacts of uncertain factors on the outputs of CDGs, which show the validity of the methodology proposed.

Keywords: Microgrid, Chance Constrained Programming, Uncertainty, Probabilistic Load Flow, Multi-Objective Optimization, Clonal Selection Algorithm.

Optimal Load Shedding Based On Line Voltage Stability Index Using Shuffled Frog Leaping Algorithm and Artificial Bee Colony Algorithm

by R. Mageshvaran, T. Jayabarathi, D. Rama Prabha

Vol. 7. n. 6, pp. 6235-6244

Abstract - Modern power systems have been operated close to their limits for reasons of economic viability. Consequently, a small increase in the load may lead to the Maximum Loading Point (MLP) of the system resulting in voltage collapse. Under such circumstances, the buses for load-shed have been selected based on line voltage stability index and its sensitivities at the operating point. This avoids voltage collapse and improves the system stability. Computational algorithms for minimum load-shed have been developed using the heuristic techniques, Shuffled Frog Leaping Algorithm (SFLA) and Artificial Bee Colony Algorithm (ABC). The algorithms proposed in the present paper are implemented on the standard IEEE 14-bus and 25-bus test systems to obtain the optimal load shedding at the selected buses when the systems are operated at their MLP. The effectiveness and efficiency of the proposed methods are established by improvements in the line voltage stability index and the bus voltages.

Keywords: Optimal Load-Shed, Voltage Stability, Line Voltage Stability Index, Optimization, Shuffled Frog Leaping Algorithm, Artificial Bee Colony Algorithm.

Fuzzy-Logic Controller for STATCOM

by A. Abderrahmani, A. Chaker, A. Laoufi

Vol. 7. n. 6, pp. 6245-6251

Abstract - This paper proposes and validates the models to accurately represent the STATCOM in voltage stability studies of power systems and the development of a fuzzy logic controller for damping oscillations in FACTS. The ability of fuzzy logic to handle rough and unpredictable real world data made it suitable for a wide variety of applications, especially, when the models or processes are too complex to be analyzed by classical methods. These models are first validated by means of MATLAB simulations on a test system, and then are implemented into two different methods used to study voltage in the system.

Keywords: FACTS, STATCOM, Modeling, Reactive Compensation, Controls Method, Fuzzy-Logic Controller.

Power System Stabilizer Design Using Interval Type-2 Fuzzy Logic Control

by Manoj Ku. Panda, G. N. Pillai, Vijay Kumar

Vol. 7. n. 6, pp. 6252-6265

Abstract - Power System Stabilizers (PSS) are added to excitation systems to enhance the damping of low frequency oscillations in power systems. In this paper interval type-2 fuzzy logic (IT2FL) is used to design power system stabilizers for single machine infinite bus (SMIB) and multi machine power systems. For controller design, membership functions of system variables are represented using interval type-2 fuzzy sets. The interval type-2 fuzzy set is capable of modeling the uncertainty and imprecision in a better way. Performance of the proposed controller in damping the low frequency oscillations is compared with that of the optimal lead lag and optimal type-1 fuzzy logic controllers. Simulation results reveal the superior performance of the proposed controller and also show the robustness of the controller with respect to system parameter variations and disturbances.

Keywords: Interval Type-2 Fuzzy Logic Controller, Particle Swarm Optimization, Power System Stabilizer, Type-2 Fuzzy Systems.

Advanced Reactive Power Control Schemes Using Static Synchronous Compensator and Adaptive Inverse Model Theory

by Tsao-Tsung Ma, Tzung-Han Shr

Vol. 7. n. 6, pp. 6266-6274

Abstract - This paper presents the design of adaptive inverse model based controllers for the static synchronous compensator (STATCOM) to perform fast reactive power regulation in power systems. The proposed control scheme is expected to provide good control features in performing various real-time reactive power flow control functions during steady-state and transient operations of power networks. The STATCOM with different hardware structures and output filter designs may have different operating modes and complex system dynamics which require advanced controllers to achieve satisfactory performances. In this paper, two separate internal model based adaptive controllers are used for controlling the STATCOM, one for the reactive power control and the other for the internal dc voltage regulation. The theoretical part of the proposed control scheme is firstly addressed then simulation and experimental studies on a simple power system embedded with a STATCOM are described. Finally, the results of a typical reactive power flow control example are presented to show the excellent control performance of the STATCOM and the effectiveness of the new control algorithm.

Keywords: Flexible AC Transmission Systems, Static Synchronous Compensator, Adaptive Inverse Model Controller.

Coordinated Dispatch of Power Generation and Spinning Reserve in Power Systems with High Wind Penetration

by Bo Yuan, Ming Zhou, Jin Zong, Gengyin Li

Vol. 7. n. 6, pp. 6275-6284

Abstract - The spinning reserve demand in high wind penetration power systems is increasing significantly due to the stochastic and unpredictable nature of wind power. On the basis of the given reliability index, expected load not supplied ratio (ELNSR), stochastic factors such as unit forced outage rate, forecast error of load demand and wind power output are synthetically considered to deduce a quantized relation between spinning reserve and system reliability demand; the derived quantized relation is then used as a constraint to build a coordinated generation and spinning reserve dispatch model. Simulation results show that the proposed model can effectively quantify system reserve demand and give optimal generation schedule as well as allocation of spinning reserve among thermal units.

Keywords: Reliability, Wind Power, Spinning Reserve, Coordinated Dispatch.

Multi-Objective Optimization of Spinning Reserve for Power System with Large Scale Wind Generations

by Yujiao Liu, Liqiong Lin, Chuanwen Jiang, Xi Jin, Yuan Ren

Vol. 7. n. 6, pp. 6285-6289

Abstract - Uncertainty of wind generations increases the difficulty of balancing cost and risk during making spinning reserve plans. To meet this challenge, this article builds a multi-objective spare optimization model with the consideration of cost expectations and conditional value at risk. And it proposes a risk decision-making model based on fuzzy theory to finalize the reserve plan. Multi-objective immune algorithm and Monte Carlo scenario simulation are used to solve the optimization algorithms. The example shows that the multi-objective model can effectively find the front-set of cost expectations and conditional value at risk; fuzzy risk decision-making model expand the effective range of the risk tolerance coefficient than the traditional one, and it can reflect the risk attitudes more clearly; the model considering both expectation and risk is more advantage than the one with just expectation from the view of risk aversion, and it can be seen as a risk management tool of decision-makers.

Keywords: Wind Energy, Spinning Reserve, Multi-Objective Optimization, Risk Management.

Using Reconfigurable System – CompactRIO in the Acquisition and Processing of Signals from Deformed Consumers

by G. Rata, M. Rata, C. Prodan, V. Chatziathanasiou

Vol. 7. n. 6, pp. 6290-6295

Abstract - Industrial development, technology modernization and automation advent, had not only beneficial but also adverse effects such as pollution harmonic of power systems and their consumers. Deforming regime is one of the very important aspects that influence power quality in power systems. Since the emergence of the harmonics in power systems, large companies producing measurement instruments made significant efforts to develop equipment for deformed consumers monitoring, which thus become more complex. An equipment that can be successfully used in the acquisition and processing of signals from deformed consumers is CompactRIO (cRIO), produced by National Instruments. This article presents an example of using a cRIO system to analyse the deforming regime generated by a three-phase consumer. For this, are realised both hardware configuration and software application in LabVIEW Real-Time, for cRIO programming.

Keywords: Power Quality, Harmonic Analysis, Total Harmonic Distortion, Programmable Automation Controllers, Monitoring.

Effect of Load Models and Voltage Step Constraint on Distributed Generation Operated at Unity and Variable Power Factors

by Rajendra P. Payasi, Asheesh K. Singh, Devender Singh

Vol. 7. n. 6, pp. 6296-6305

Abstract - The optimum location and size of distributed generation (DG) are affected with many factors. Some important factors, which must be considered in distributed generation planning (DGP), are load model, seasonal variations in load, and voltage step constraint. In previous works, the load model and voltage step constraint are considered separately by different authors. Further, the effect of voltage step on size of DG has been considered for fixed locations and particular operating power factor of DG. In this paper, the voltage step constraint, load model, and seasonal variations in load are considered together. An investigation into optimal location, size, and power factor of DG considering voltage step constraint and mixed load model is performed. The types of DGs capable of delivering real power as well as capable of delivering both real and reactive power are compared. The investigation shows that voltage step constraint is more effective for constant power load model, and the optimum size of DG may also increase with optimum location, instead of decrease.

Keywords: Distributed Generation, Distribution System, Distributed Generation Planning.

Design and Implementation of a Hybrid Power Interface for Advanced Micro-Grid Operation and Control

by Tsao-Tsung Ma, Tian-Huei Wu

Vol. 7. n. 6, pp. 6306-6316

Abstract - This paper presents a novel design concept, in which a hybrid power interface system (HPIS) is constructed to work smartly in various micro-grid (MG) operations. Some distributed generation (DG) systems, e.g., the wind turbine generator (WTG) and the PV solar system conventionally generate real power based on natural conditions thus the average utilization rate of the entire asset is normally low. To eliminate this shortcoming, the proposed HPIS aims to use the DG inverter system optimally. To achieve a cost effective design, a three-leg zigzag transformer is incorporated into the proposed HPIS to maximize the operating capability of DG inverter in terms of real power regulation, active power filter (APF) functions for current harmonics compensation and reactive power compensator for MG voltage support and power factor compensation. The HPIS is designed to fully utilize the DG inverter capacity that remaining after real power generation for accomplishing various control functionalities required by the system operator. In this paper, the mathematical model of HPIS and its related controllers designed in two-axis stationary reference frame are firstly addressed. Simulation studies on a simplified MG network are carried out and followed by a set of experimental tests on dSPACE1104. Typical results are presented with brief discussions to demonstrate the feasibility and effectiveness of the proposed control scheme.

Keywords: Hybrid Power Interface System (HPIS), Distributed Generator (DG), Micro-Grid (MG), Active Power Filter (APF).

PMU-based Voltage Stability Assessment in Microgrids by ANNs Considering Single Contingencies

by M. Gholami, M. J. Sanjari, G. B. Gharehpetian

Vol. 7. n. 6, pp. 6317-6323

Abstract - In this paper, the voltage stability assessment of the microgrid based on PMU data is discussed. In the best case, all buses in a microgrid are observable, but the cost of the monitoring system is high. In this paper, it is assumed that the economical saving or failure of PMUs would result in non-complete observability. Two methods, named as indirect and direct methods presented in this paper for the voltage stability assessment in normal and single contingency conditions. The proposed methods are applied to MG 15-Bus and MG 9-Bus systems. The results show that in the cases with less unobservable buses, the direct method is better than indirect method and in the cases with more unobservability the indirect method results in a better voltage stability assessment.

Keywords: Microgrid, PMU, Incomplete Observability, Artificial Neural Network, Voltage Stability Assessment.