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International Review of Electrical Engineering - February 2009 - Papers

Implementation of New Control Method based on Dynamic Evolution Control for DC-DC Power Converter
A Novel Design and Application of a Single Phase Multilevel Inverter
Performance Specifications of Series-Parallel UPS’s with Different Control Strategies
Experimental Investigation of High Frequency Oscillations Due to Voltage Notch of AC/DC Converters
Topology and Controller of a New Three-Phase Buck-Boost Inverter
Development of Digital Burn-In Test Plant for DC-DC Converter with Energy Recycling Considered
On the Modeling in Transient FEA of SMPM with Coupled Inverter
Synchronised Space-Vector Modulation for Six-Phase Automotive Drive with Controlled Switching Frequency
Driving/Regeneration and Stability Enhancement for a Two-Wheel-Drive Electric Vehicle
New Device to Adjust On Load the Voltage Level at Power Transformers
Voltage Regulation with a Dynamic Voltage Restorer Using Reactive Power for Low DC Energy Storage Utilization
Performance Investigation of Load Shed Scheme for a Real Power System using a Distributed-Dynamic Model
Sub-Synchronous Resonance Damping in Total Variation Ranges of Operating Conditions Using a STATCOM
An Investigation of the Applicability of Barbed Shield Wires to Protect Transmission Lines Using Charge Simulation Method
A Novel Mathematical-Heuristic Method for Non-Convex Dynamic Economic Dispatch
Application of a Novel Real Genetic Algorithm to Accelerate the Distribution Network Reconfiguration
A New Fuzzy Power Flow Analysis Based on Uncertain Inputs
Investigation of Dynamic Instability of Torsional Modes in ‎Power System Compensated by SSSC and Fixed Capacitor
A New Method for Fast Computation of Maximum Loading Margin Utilizing the Weak Area of the System
Behavioral Study of Stress in Toroidal, Solenoidal, and Helical Toroidal Coils with Similar Ring Structures for Reactor Plasma

International Review of Electrical Engineering - Papers

Implementation of New Control Method based on Dynamic Evolution Control for DC-DC Power Converter

by A. S. Samosir, A. H. M. Yatim

Vol. 4. n. 1, pp. 1-6

Abstract - This paper proposes a new control technique for dc-dc power converter. Design and implementation of the proposed control method for dc-dc power converter is provided. A new approach for converter controllers synthesis based on dynamic evolution control theory is presented. In order to synthesize the converter controllers, this method uses a simple analysis of non linear equation models of the converter. The synthesis process is simple and requires a quite low bandwidth for the controller. Therefore, this control method is suitable for digital control implementation. In this paper, synthesis example of boost dc-dc converter is discussed in detail. DSP based Controller algorithms for these converters are implemented. Performance of the proposed dynamic evolution control under step load variation condition is tested through simulation and experimental. Simulation and experiment results show that the proposed techniques are suitable for controlling dc-dc power converter.

Keywords: Dynamic evolution control, New control method, Non linear control.

A Novel Design and Application of a Single Phase Multilevel Inverter
by E. Beser, B. Arifoglu, S. Camur, E. Kandemir Beser

Vol. 4. n. 1, pp. 7-13

Abstract - In this paper, a novel topology for single-phase multilevel inverter is introduced. Structural parts of the inverter are described in detail. Switching strategy and operational principles of the proposed inverter are explained and operational topologies are respectively given for 7-level inverter structure for simplicity. A method and a formula are improved to calculate switching angles for multilevel inverters. By improved formula switching angles can be calculated easily. And another equation gives switch number related to level number is obtained and used for multilevel topologies. Proposed topology is simulated for 7, 15, 31 and 63-level inverters and simulation results of output voltage are given. For verifying the validity of the proposed inverter a prototype is manufactured, experimental studies are realized for all simulated levels and also experimental results are given. Additionally, total harmonic distortion (THD) values are calculated and measured related to level number. All results are given in tables, comparatively. It is seen that from the results, the proposed inverter generates a high-quality output voltage wave form. By increasing level number, THD decreases even for resistive loads. In addition, this multilevel inverter structure reduces dv/dt stresses imposed on power-switching devices and also harmonic components of output voltage.

Keywords: Multilevel Inverter, Single Phase Inverter, Total Harmonic Distortion.

Performance Specifications of Series-Parallel UPS’s with Different Control Strategies
by Mehdi Niroomand, Hamid R. Karshenas

Vol. 4. n. 1, pp. 14-21

Abstract - In this paper, two control strategies for three-phase Series-Parallel Uninterruptible Power Supplies (SP-UPS) are described and compared. An SP-UPS consists of a parallel and a series converter, and most of the power required by load is supplied directly from ac input line during standby mode. Therefore, the overall efficiency is increased as compared to conventional UPS’s. The first control strategy proposed for SP-UPS was based on voltage control of series converter and current control of parallel converter. However, recently an opposite strategy has been proposed, i.e., voltage control of parallel converter and current control of series converter. This paper compares these two control strategies. The comparison is made based on different performance criteria like seamless transition between backup and standby modes, dynamic performance, reference generation and the size of filters.

Keywords: Series-parallel UPS, Delta conversion UPS, Seamless transition.

Experimental Investigation of High Frequency Oscillations Due to Voltage Notch of AC/DC Converters
by R. Ghandehari , A. Shoulaie

Vol. 4. n. 1, pp. 22-29

Abstract - This paper is concerned with the problems generated by voltage notch in the voltages of converter bus and adjacent buses. Voltage notch disturbs voltages waveform and excites the natural frequencies of systems. In systems with low short circuit level, these excitations create considerable high frequency oscillations on the voltages of converter and the buses that are in vicinity of converter bus, which can damage capacitor banks, create parallel resonance, generate radio disturbances, and make malfunctioning of electronic devices. This paper analyzes voltage notch based on AC/DC converter circuit and system parameters. Effect of snubber circuits on the voltage oscillations arising from commutation are investigated, and theoretical foundation and analytical derivation are presented to calculate frequency of oscillations and notch depth. A benchmark model is introduced, and voltage notch analysis is performed by theoretical foundation and computer simulation. Comparing the results obtained from both theoretical method and simulation confirms the proposed equations, properly. Several experimental results are shown in order to illustrate the effect produced by changes on system and converter parameters on the voltages waveform of converter. Computer simulations and experimental results indicate the accuracy of theoretical relations. The proposed equations make it possible to effectively study harmonic and power quality in networks that include high power converters.

Keywords: Voltage notch, AC/DC converters, High frequency oscillations, Local networks.

Topology and Controller of a New Three-Phase Buck-Boost Inverter
by B. Koushki, J. Ghaisari, M. Saghaian Nejad

Vol. 4. n. 1, pp. 30-35

Abstract - Classical three phase inverters are not capable to produce AC output voltage greater than DC input voltage. In many applications such as electrical drives with photovoltaic input, DG with low voltage input sources, and three-phase UPS, AC output voltage of inverter should be greater than the DC input voltage. There are different approaches to overcome this problem. In this paper a new three-phase inverter which can boost its input voltage is proposed. This converter has lower devices voltage ratings in compare with other methods. The proposed topology is based on three individual buck-boost DC-DC converters. Sliding mode controller is also design and applied to the inverter. Simulation and experimental results for different conditions such as load variations as well as nonlinear loading verify the correctness of the circuit and its controller.

Keywords: Buck-Boost Inverter, sliding mode, Three-Phase Inverter.

Development of Digital Burn-In Test Plant for DC-DC Converter with Energy Recycling Considered
by K. I. Hwu, Y. H. Chen

Vol. 4. n. 1, pp. 36-44

Abstract - An active load for the burn-in test of the DC-DC converter, possessing multiple inputs with a wide range of input voltages, is proposed herein, whose controller is realized by a digital signal processor (DSP). By means of DSP, data monitoring and command setting are easy to realize. First of all, the details of the proposed circuit topology and the corresponding control strategy are presented. Finally, some experimental results are provided to demonstrate the proposed burn-in test plant.

Keywords: : Active Load, Burn-In Test, DC-DC Converter, DSP, Energy Recycling, Multiple Inputs, Wide Range of Input Voltages.

On the Modeling in Transient FEA of SMPM with Coupled Inverter
by M. H. Gmiden, H. Trabelsi

Vol. 4. n. 1, pp. 45-49

Abstract - This paper presents the finite element analysis (FEA) for the dynamic characteristics of an inverter-fed surface mounted permanent magnets motor SMPM. A direct coupling is used to connect finite element model and circuit model. The time-stepping finite element method (FEM) and the moving mesh technique are used for the transient simulation with a PWM current control. The algorithm of iteration process is done. The field distribution, the modulated waveforms for three phases and the currents supplied by coupling inverter to SMPM motor are checked.

Keywords: Finite Element Method, SMPM, Inverter, PWM, Coupled circuit.

Synchronised Space-Vector Modulation for Six-Phase Automotive Drive with Controlled Switching Frequency
by Valentin Oleschuk, Giovanni Griva

Vol. 4. n. 1, pp. 50-56

Abstract - The paper presents results of analysis of operation of six-phase (dual three-phase) traction drive on the base of asymmetrical induction motor which has two sets of windings spatially shifted by 30 electrical degrees, and two three-phase inverters, supplied by two isolated DC sources (Fuel Cells + Battery). Novel control strategy for this drive topology is based on variation of switching frequencies of each inverter in dependence on the magnitudes of voltages of the corresponding DC sources. Basic schemes of synchronised pulsewidth modulation (PWM), applied for control of the two voltage source inverters with different switching frequencies, allow continuous voltage synchronization in systems and improved spectral composition of the phase voltages. Simulations show a behavior of the systems with continuous and discontinuous versions of synchronised PWM.

Keywords: Asymmetrical Six-Phase Motor, Modulated Dual Inverters, Voltage Synchronization.

Driving/Regeneration and Stability Enhancement for a Two-Wheel-Drive Electric Vehicle
by P. Naderi, M. Mirsalim, S. M. T. Bathaee

Vol. 4. n. 1, pp. 57-65

Abstract - In-wheel motors are revolutionary electric drive systems which can be considered as zero emission vehicle designs. Enhanced safety can be obtained by independent torques applied to the driven wheels. In the other hand, Driving/Regeneration can be achieved by adding the torques.
This paper presents a Driving/Regeneration and direct yaw -moment control on each rear in-wheel machine of an electric vehicle. By a seven-degree model for vehicle modeling, and using reference yaw-rate from bicycle theory, a sliding mode controller is designed for calculation of the difference
between the applied torques. Driving/Regeneration is implemented by taking advantage of adding the torques which are determined based on pedals displacements and a fuzzy controller. The novelty aspects of this research are to consider the effects of Acceleration/Brake pedals’ maneuvers by
means of vehicle forward simulation, and implementing simultaneous Driving/Regeneration and yaw-moment control of typical electrical devices which has not been discussed in previous articles.The effectiveness and accuracy of the proposed structure is confirmed by the results of a series of
simulations and also comparison with a well known method.

Keywords: Vehicle, Yaw control, In-wheel motor, Driving/Regeneration, Sliding mode.

New Device to Adjust On Load the Voltage Level at Power Transformers
by A. Pleşca, M. Adam, A. Baraboi, C. Pancu

Vol. 4. n. 1, pp. 66-74

Abstract - Many industrial activities and also our nowadays life utilities such as lighting system or different electronic devices request a constant voltage level or a little variation between certain admissible limits. It is a real problem when it takes into account that more and more customers use PCs or network system PCs because it is well known that these kind of systems need a constant voltage supply level. With this aim it was achieved a new device with the possibility to make on-line step voltage regulation and/or continuous voltage adjustment. The proposed voltage regulator maintains the constant voltage on the load under the conditions of input voltage and/or load current variations.

Keywords: Voltage regulation, On load tap changers, Power transformers.

Voltage Regulation with a Dynamic Voltage Restorer Using Reactive Power for Low DC Energy Storage Utilization
by Mario González, Víctor Cárdenas, Nancy Visairo

Vol. 4. n. 1, pp. 75-85

Abstract - A single-phase dynamic voltage restorer that applies two functions for voltage regulation is proposed in this paper. Load voltage regulation using reactive power (RRP) is proposed to be used together with the classical restoration function using active power. The RRP function can be used to compensate swells, and some sag cases if the load power factor allows its possibility. The use of reactive power to regulate the load voltage means that no energy is needed to be provided from or absorbed by the capacitor bank energy storage. This is accomplished by making the compensation voltage to be in quadrature with the fundamental component of the system current. This gives a significant advantage, since the equipment can compensate swells without the need of regeneration, of the oversizing of the dc link, or of dissipation means; and can compensate sags without using the energy of the storage. For the sag cases where the RRP is not possible to apply, the classical restoration function using the active power of the energy storage is activated, injecting the missing voltage in back phase. Generation of references, limitations, a scheme of operation, and practical simulations results are presented.

Keywords: Dynamic voltage restorer, Power quality, Voltage regulation, Sag, Swell.

Performance Investigation of Load Shed Scheme for a Real Power System using a Distributed-Dynamic Model
by M. Sanaye-Pasand, M. R. Dadash Zadeh

Vol. 4. n. 1, pp. 86-93

Abstract - Load shedding schemes are important and powerful tools in the present day power systems to maintain system stability. Loss of system major sources or loss of critical interconnections could cause mismatch between system load and generation. In order to cover this mismatch, load shedding schemes using under frequency relays shed sufficient amount of loads to avoid frequency drop and maintain system stability. They have become quite important in the present day systems where there is lack of adequate spinning reserve margin and shortage of tie line capacity to make up for loss of generation. Reliability and optimization of load shedding schemes depend on power system dynamic characteristic. In this research work, one of the major parts of a real power system has been selected for dynamic load shedding studies. Suitable software has been used for dynamic simulations and the power network is modeled appropriately in distributed form including transmission lines, generators, AVRs, governors, under frequency relays and loads. Various events such as loss of generator and combinational events under different system conditions have been modeled and performance of the load shedding algorithm has been evaluated. It is observed that as system voltage and frequency variables are related to each other, it would be helpful to consider the effect of decline in both voltage and frequency simultaneously to design a reliable and complete load shedding scheme.

Keywords: Load shedding, Power system modeling, Blackout, Combinational events, Voltage stability.

Sub-Synchronous Resonance Damping in Total Variation Ranges of Operating Conditions Using a STATCOM
by H. Khalilinia, J. Ghaisari

Vol. 4. n. 1, pp. 94-101

Abstract - Sub-Synchronous Resonance (SSR) in long transmission line brings on failure of the turbine shaft if not damped properly. STATic COMpensator (STATCOM) is a multifunctional FACTS device which its abilities depend on its location on transmission line. The main purpose of this work is damping SSR using STATCOM. To reach this goal a controller is proposed and designed for a STATCOM in transformer bus. In addition to SSR damping, the STATCOM with proposed controller can improve power oscillations and first swing stability. Eigenvalues analyses and nonlinear simulations in PSCAD/EMTDC software are used to illustrate the proposed controller and STATCOM performance. The simulation results approve the proposed scheme capability to damp SSR in total variation ranges of operation points.

Keywords: Sub-Synchronous Resonance (SSR), STATCOM, Damping Control.

An Investigation of the Applicability of Barbed Shield Wires to Protect Transmission Lines Using Charge Simulation Method
by B. Vahidi, S. Taghipour Boroujeni, S. M. Ahadi

Vol. 4. n. 1, pp. 102-107

Abstract - The effectiveness of existing methods of lightning protection has come into question recently. In this paper, a new method and device have been introduced that can be useful in lightning protection. A theoretical study of the performance of barbed shield wires versus common shield wires is reported. The computation was conducted on 230 kV transmission line using charge simulation method (CSM) and leader progression model in order to find the striking point on transmission line. In this simulation the effects of the sag of line as well as space charge are considered. The results demonstrate the ability of the barbed shield wire in reducing the number of lightning strokes to phase conductors.

Keywords: Barbed shield wire, Common shield wire, Transmission line, Lightning protection, Phase conductor.

A Novel Mathematical-Heuristic Method for Non-Convex Dynamic Economic Dispatch
by Seyed Hamid Hosseini, Ahmad Salehi Dobakhshari, Reza Jalayer

Vol. 4. n. 1, pp. 108-113

Abstract - Dynamic economic dispatch (DED) determines system generation schedule in a specified time interval to meet load demand at each hour while satisfying generation system constraints. DED considering valve-point effects is a non-convex optimization problem and therefore conventional mathematical methods fail to solve this problem. This paper presents a hybrid gradient search - near optimal search method to solve the DED problem considering valve-point effects of generating units. Local minima obtained by Gradient Search Method (GSM) are utilized by a novel Near Optimal Search (NOS) method to find the global optimum of the DED problem. The efficiency and feasibility of the proposed method and its dominance over other heuristic methods are illustrated by application to the ten-unit test system with non-convex cost functions.

Keywords: Dynamic economic dispatch, Valve-point effects, Gradient search method, Near optimal search.

Application of a Novel Real Genetic Algorithm to Accelerate the Distribution Network Reconfiguration

by Saeed Jazebi, Sahar Jazebi, Masoud Rashidinejad

Vol. 4. n. 1, pp. 114-121

Abstract - Distribution network reconfiguration (DNR) is a crucial issue especially in the operating scheme of distribution systems. In distribution networks tie switches will be changed in order to facilitate an appropriate configuration satisfying minimum losses. Many researches have been focused on developing evolutionary search algorithms to enhance the convergence rate associated with better performance. In order to achieve a global optimum in less computational effort in network reconfiguration, a novel Real Genetic Algorithm (RGA) is proposed in this paper. To validate the proposed method, it is compared with Differential Evolution Algorithm (DEA) solving the same problem. Both RGA and DEA are applied to the 69-bus and 83-bus distribution test systems. Simulation results regarding computational time validate a significant performance of RGA in comparison with DEA. Case studies and results analysis show the effectiveness of the proposed methodology for DNR problem.

Keywords: Distribution Network, Power Losses, Reconfiguration, Real Genetic Algorithm, Differential Evolution Algorithm.

A New Fuzzy Power Flow Analysis Based on Uncertain Inputs

by M. Sadeghi Sarcheshmah, A. R. Seifi

Vol. 4. n. 1, pp. 122-128

Abstract - In this paper, a new method for uncertainty analysis in fuzzy power flow is proposed. The uncertainty is expressed in both loads and generations. Uncertainties in both loads and generations are modeled with different fuzzy membership functions (triangular and trapezoidal). To find the fuzzy distribution of any state variable, the problem is formulated as a constrained linear programming (LP) optimization. The viability of the proposed method would be verified with the ones obtained from the conventional power flow and the fuzzy power flow (FPF) in the 6-bus system and in the IEEE-30 bus system.

Keywords: Linear Programming, Load Flow Analysis, Uncertainty, Fuzzy Distribution.

Investigation of Dynamic Instability of Torsional Modes in ‎Power System Compensated by SSSC and Fixed Capacitor
by R. Hooshmand, M. Azimi

Vol. 4. n. 1, pp. 129-138

Abstract - The torsional mode is one of the power system problems which may lead to dynamic ‎instability in them. In this paper, a static synchronous series compensator (SSSC) along with a ‎fixed capacitor is used in order to avoid torsional mode instability in a series compensated ‎transmission system. For this purpose, a 6-step harmonic neutralized inverter is used for ‎realization of the SSSC. Also, the IEEE first benchmark model on SSR analysis is considered ‎as the case study. The system dynamic stability is studied through EMTDC/PSCAD ‎simulation studies. The presence of the fixed capacitor ensures increased damping of small ‎signal oscillations. At higher levels of fixed capacitor compensation, a damping controller is ‎required to stabilize the torsional modes of SSR. It is shown that the combination of the SSSC ‎and the fixed capacitor improves the damping oscillations.

Keywords: Power System Stabilizer (PSS), Robust Stability, Linear Matrix Inequality (LMI) Problem.

A New Method for Fast Computation of Maximum Loading Margin Utilizing the Weak Area of the System
by S. Hasanpour, R. Ghazi, M.H. Javidi

Vol. 4. n. 1, pp. 139-145

Abstract - Voltage stability has become a very important issue for operating power systems close to their limits due to the continuous load increase and economic constraints. This paper discusses some important aspects related to the maximum loading margin in voltage stability studies and proposes a new method for fast and accurate calculation for maximum loading margin. The proposed method is based on an optimization technique in which the genetic algorithm is utilized to solve the parameterized nonlinear load flow equations. To reduce the computational burden, the optimization problem is examined in the weak area of the system as a subsystem which is defined by modal analysis. The proposed method is simple, efficient and quite fast for determining the maximum loading margin. Therefore it will be a suitable approach for online assessment of voltage stability problem. Simulation results for IEEE 14, 30 and 57 bus systems are shown to validate the proposed method.

Keywords: Genetic Algorithm, Maximum Loading Margin, Modal Analysis, Saddle Node Bifurcation, Voltage Stability, Weak Area.

Behavioral Study of Stress in Toroidal, Solenoidal, and Helical Toroidal Coils with Similar Ring Structures for Reactor Plasma
by M. R. Alizadeh Pahlavani, A. Shoulaie

Vol. 4. n. 1, pp. 146-158

Abstract - In contrast to pure solenoidal and toroidal coils, helical toroidal coils can be designed in a way to eliminate or balance stress in certain coordinate directions. With respect to the fact that calculation of inductance is the basis for the optimal design of helical toroidal coils, this work is focused on developing relations for self and mutual inductance of the these coils at superconductivity conditions based on Newman's equation. The target functions for the optimal design of these coils include maximization of the ratio of the stored magnetic energy to the conductor's mass or toroid volume, elimination or balancing stress in some coordinate directions, or the attenuation of the leakage flux. It is demonstrated that the self and mutual inductance can be calculated in the same way provided that 0.4 of the minor radius is greater than the diameter of the conductor’s cross section and that the definition of the mean geometrical radius at superconductivity is applied. Comparison between the experimental and calculated results for inductance shows that the presented equations in this work are highly reliable. Sketching contours for magnetic flux density indicates that a special approach must be taken so that the coil can eliminate the leakage flux.

Keywords: Superconductor, semi-toroidal coordinate system, helical toroidal coil, inductance calculation, behavioral study of magnetic flux density components.