The IJPEAI Journal

Abstract: This paper presents a new transient stability index called the Area-based COI-referred Transient Stability Index for a large electrical power system. A large power system is divided into smaller areas depending on the coherency of the system due disturbances before the index is applied on the system. The proposed index is defined by associating with each area of the power system an equivalent inertia representing the total inertia of the generation located in that area. Assuming that each area is coherent, it is possible to assimilate its behavior to that of a single large machine with same inertia and generation. It also offers a direct means of deriving the centre of inertia (COI). The COI provides very useful information for tracking the stability of interconnected areas. So, instead of assessing all generators' rotor angles in the system, the index reduced to only assessing the single large machine rotor angle's representing each area. Simulations on the 275 kV Malaysia 's power system show the effectiveness of the proposed index.

Index Terms: transient stability index, transient stability assessment, time domain simulations.

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Design Optimization of 3-Phase Rectifier Power Transformer by Genetic Algorithm and Simulated Annealing 

K. S. Rama Rao, K. N. Md. Hasan

Abstract: This paper presents the design optimization, by Genetic Algorithm (GA) and Simulated Annealing (SA), of a 3-phase rectifier power transformer supplying a dc load. A closed form expression for actual phase current waveform of the rectifier transformer is used and a comparison is made with the approximate waveform normally considered for fixing the transformer rating. Two non-linear programming techniques, GA and SA are applied for the estimation of transformer design parameters and the results are compared. The optimal results demonstrated by an example show the potential for implementation of GA as an efficient search technique for design optimization of transformers. A discussion on the limitations and variation of GA parameters while minimizing the single and multi-objective functions satisfying the performance constraints on the proposed optimal design concludes the paper.

Index Terms: Semi-conductor rectifier power transformers, non-sinusoidal currents, nonlinear programming, genetic algorithm, and simulated annealing.

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Comparing the Network Performance between the Installation of DG and Compensating Capacitor using EP

S. R. A. Rahim , T. K. A. Rahman, I. Musirin, S. A. Azmi, 
M. F. Mohammed,  M. H. Hussain,  M.Faridun

Abstract: Rapid industrialization and population growth have resulted in an escalation in the electrical power demand. Due to limited area and slow progress in network expansion some regions have become high density load areas, for example in the urban areas. These phenomena may lead to power quality and also voltage stability issues. This paper presents the performance improvement in distribution network with distributed generation (DG). Pre-developed sensitivity index was utilized to identify the suitable location of distributed generation installation; followed by optimization of the distributed generation output to obtain maximum benefits from its installation using EP. Consequently, installation of capacitor was also implemented to perform similar task. The compensating capacitor was installed at the bus location identified by the sensitivity analysis. The effectiveness of the proposed methodology was validated on the 33-Bus Distribution System. Results for loss minimization and voltage profile improvement produced by the distributed generator allocation with those obtained by installing the compensating capacitor in the system were compared accordingly in order to reveal the merit of each technique.

Index Terms: Distributed Generation (DG), Sensitivity analysis, Evolutionary Programming (EP)

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A  Comparative Study of Modulation Schemes for Cyclo-Inverters

V. Agarwal, A. Agarwal

Abstract : Three modulation techniques namely Sinusoidal PWM, Space Vector PWM and Delta Modulation have been applied in cyclo-inverter for reducing harmonics in the output. It has been found that for Sine PWM, for modulation index, m, around 0.5 to 1, the minimum total harmonic distortion factor (THD) obtained is 10 %. The harmonic contents in the cyclo-inverter output gradually increase when m is less than 0.5.  Cyclo-inverter output improves for delta modulation scheme where the total harmonic distortion is found to be 4% when modulation index is lying from 0.75 to 1.5. Any further increase or decrease in modulation index increases the harmonics in cyclo-inverter. Similarly, for Space Vector PWM, THD has been also found to be as low as 5%. Since Delta modulation can be smoothly tuned to the designer's priorities and varying operating conditions by simple parametric adjustments, without any modifications of the timing structure it is recommended in cyclo-inverters as compared to Sinusoidal PWM and Space vector PWM both in terms of switching losses as well as harmonic reduction.

Index Terms : Delta Modulation, Space Vector Modulation, Cyclo-Inverter, Harmonic Reduction, Total harmonic distortion.

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Automatic Generation Control of Power System with Fuzzy Gain Scheduling Integral and Derivative Controller

L. H. Hassan, H.  A. F. Mohamed, M. Moghavvemi, S. S. Yang

Abstract : This paper presents a new Fuzzy Gain Scheduled Integral and Derivative (FGID) controller for Automatic Generation Control (AGC) of a two area non-reheat power system. Simulation results show that the proposed control scheme is suitable for damping the frequency oscillation due to load disturbance effects. The proposed controller is compared against other controllers using settling times, overshoots, and undershoots of the frequency deviations. The results show that the proposed controller outperforms other schemes. Best dynamic responses are obtained when compared with Fuzzy Gain Scheduling of Proportional and Integral (FGPI) controller, fuzzy controller, and Conventional Proportional and Integral (PI) controller.

Index Terms : Automatic generation control, fuzzy logic control, power system.

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Optimum Tuning of Power System Stabilizers via CDCARLA Optimization Technique

M. Kashki, Y. Abdel-Magid

Abstract : One of the effective methods of damping low-frequency oscillations in power systems is the utilization of power systems stabilizers (PSS). This paper demonstrates the use of a novel technique knows as combinatorial discrete and continuous action reinforcement learning automata (CDCARLA), to optimally tune the parameters of a power system stabilizer. A single-machine infinite bus system is considered to demonstrate the suggested technique. Simulation results show that the proposed power system stabilizer is effective and robust.

Index Terms : Power system stabilizer, PSS, Reinforcement learning automata, SMIB, Dynamic stability.

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Application of SVC Device for Damping Oscillations Based on Eigen Value Techniques

N. Magaji, M. W. Mustafa

Abstract : SVC devices are used to improve voltage and reactive power conditions in ac systems. An additional task of SVC is to increase transmission capacity as result of power oscillation damping. Eigenvalue-based methods for analysis and control of power system oscillations using SVC have been developed. The characterization of power system oscillations using the eigenvalues and eigenvectors of the state matrix is detailed. Design of power system damping controllers using residue method is addressed.

Index Terms : SVC, Power system oscillations, linear models, eigenvalues, eigenvectors, participation factors, residues.

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Abstract: Power system engineers are continually faced with the problem of handling large-scale networks arising due to system expansion and greater interconnections. Large-scale systems can be solved using piecewise solution technique wherein the original system is torn into several subsystems, each subsystem is solved independently and the solutions of subsystems are tied up to obtain the total solution. In the proposed method, impedance parameters are consistently used to solve power flow problem of large power systems. The inverse of the Jacobian matrix of each subsystem is derived from the bus impedance matrix of that subsystem. The effect of the cut elements are accounted through proper power injections. The proposed power flow method is successfully tested on IEEE standard systems and found to give good results.

Index Terms: Large-scale Power System Problems, Piecewise Method, Power Flow Solution, Impedance Parameters.

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Abstract: Bus admittance matrix is invariably used for the power flow solution. In this paper, power flow analysis that makes use of only impedance parameters is presented. The inverse of Jacobian matrix is obtained very easily by doing simple mathematical operations on the bus impedance matrix of the transmission network. This constant J-matrix is used to update the solution in each iteration. The proposed method is tested on IEEE systems and found to give good results. As compared to the Fast Decoupled Power Flow method, the proposed one takes lesser number of iterations to get the exact solution. The proposed power flow method can be extended to solve power flow problem associated with large power systems, using piecewise solution technique.

Index Terms: Power Flow Solution, Impedance Parameters, Faster Solution.

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 Improving Speed Control of Induction Motors Through Fuzzy-SMC-PI Control

H.  A. F. Mohamed, E. L. Lau, Lokman H. Hassan, S. S. Yang, M. Moghavvemi

Abstract : This paper presents the design a of Fuzzy-SMC-PI controller to improve the speed control of induction motors. By combining a sliding mode control and a PI controller through fuzzy logic, the resulting regulator solves the problems of overshoot and slow transient responses associated with fast response PI controllers in transient state and the chattering problem associated with robust sliding mode controllers in the steady state. In this strategy, Sliding Mode Control (SMC) is responsive during transient state while PI control becomes fully active in the steady state area. The combination of both control strategies through fuzzy logic provides a mean to create a hybrid control strategy that produce minimum overshoot, faster settling time and an almost chatter free system. Simulations of the proposed Fuzzy-SMC-PI strategy on the flux and speed controllers display diminished chatter, overshoot and significant reduction of settling time. One other significant result of applying Fuzzy-SMC-PI strategy on the flux component of the system is that optimum flux level is attained fairly quicker. This results in faster rise and settling times.

Index Terms : Induction motor flux and speed control, electric drives, sliding mode control, sliding control.

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ARMA versus AR in Short Term Load Forecast

Z. Baharudin, N. Kamel,  I. Musirin

Abstract : Short-term load forecasting plays an important role in planning and operation of power system. The accuracy of this forecasted value is necessary for economically efficient operation and also for effective control. This paper describes a comparison of autoregressive moving average (ARMA) and autoregressive (AR) Burg’s and modified covariance (MCOV) methods in solving short term load forecast. The methods are tested based on historical load data of New South Wales, Australia. The accuracy of discussed methods are obtained and reported.

Index Terms : Short term load forecasting (STLF), autoregressive (AR), Autoregressive moving average (ARMA), Burg, MCOV, Durbin, MAPE.

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