azah mohamed - National University of Malaysia (original) (raw)

Papers by azah mohamed

Output power fluctuation of photovoltaic (PV) sources is a problem of practical significance to u... more Output power fluctuation of photovoltaic (PV) sources is a problem of practical significance to utilities. To mitigate its impacts, particularly on a weak electricity network, a battery energy storage (BES) system can be used to smooth out and dispatch the output to the utility grid on an hourly basis. This paper presents an optimal control strategy of BES state-ofcharge feedback (SOC-FB) control scheme used for output power dispatch of PV farm. The SOC-FB control parameters are optimized by using heuristic optimization techniques such as genetic algorithm (GA), gravitational search algorithm (GSA), and particle swarm optimization (PSO) in Matlab. In addition, an improved BES model is developed in PSCAD/EMTDC software package, in which GA is used to evaluate the optimal parameters. The studied multi-objective optimization problem also considers the evaluation of the optimal size of the BES. The performance of the proposed optimal SOC-FB control scheme is validated by comparing the results obtained from Matlab and PSCAD/EMTDC and with results from previous works. Finally, the best set of parameters are used to further validate the proposed method by using data obtained from the actual output of a grid-connected PV system. .my (M.Z. Daud), azah@eng.ukm.my (A. Mohamed), asrul@eng.ukm.my (A.A. Ibrahim), hannan@eng.ukm.my (M.A. Hannan). Measurement 49 (2014) 15-25

Artificial neural network approach to network reconfiguration for loss minimization in distribution networks

... configuration. The accuracy of the ANN results indicates that the ANN model can be a useful t... more ... configuration. The accuracy of the ANN results indicates that the ANN model can be a useful tool for solving online realtime network reconfiguration problems so that the loss reduction of the distribution system is achieved. The ...

LOSS REDUCTION IN DISTRIBUTION NETWORKS USING NEW NETWORK RECONFIGURATION ALGORITHM

Electric Machines and Power Systems, 1998

Network reconfiguration is an operation task, and consists in the determination of the switching ... more Network reconfiguration is an operation task, and consists in the determination of the switching operations such to reach the minimum loss conditions of the distribution networks. In this paper, a general formulation of the network reconfiguration for loss minimization is given for the optimization of distribution loss reduction and a solution approach is presented. The solution employs a search over

Electric Power Systems Research, 2005

One of the concepts in restructuring the electric power industry is the ability to accurately and... more One of the concepts in restructuring the electric power industry is the ability to accurately and rapidly quantify the power transfer so-called as the available transfer capability (ATC). Accurate identification of ATC provides vital information for both planning and operation of the bulk power market in reserving transmission services. There are various methods used to determine ATC such as the DC power flow, AC power flow, optimal power flow and sensitivity techniques. These methods considered the transmission line and voltage limits as the constraints for ATC computation. This paper presents the determination of power transfer between two buses that takes into account the dynamic security constraint. The dynamic security constraint based transient stability has been found to be one of the limiting factors in determining the power transfer so-called as the available transfer capability (ATC). The multi-machine integral square generator angle (ISGA) index is used to measure the severity of stable and unstable transient events during the occurrence of line outage and it is considered as the dynamic security constraint of the ATC assessment. The determination of ATC considering dynamic security constraint has been performed on the 6 bus and 11 bus systems. Comparative study has been made between the cubic-spline interpolation technique and recursive AC power flow method in determining the value of ATC.

Based on the fact that PV systems are clean, environment friendly and secure energy sources, PV s... more Based on the fact that PV systems are clean, environment friendly and secure energy sources, PV system installation has played an important role worldwide. However, the drawback of PV system is the high capital cost as compared to conventional energy sources. Currently, many research works are carried out focusing on optimization of PV systems so that the number of PV modules, capacity of storage battery, capacity of inverter, wind turbine capacity as well as diesel generator size optimally selected. In this paper, the current status of research on PV systems size optimization is reviewed taking into account standalone PV systems, hybrid PV/diesel generator systems, hybrid PV/wind systems, hybrid PV/wind/diesel generator systems as well as grid connected systems. In addition, size optimization techniques for the inverter in PV systems are reviewed. The outcome of this paper shows that the optimization of PV system is strongly depends on meteorological variables such as solar energy, ambient temperature and wind speed. Furthermore, the numerical methods are the mostly used methods. Meanwhile the artificial intelligence techniques have been employed recently to improve the process of PV system size optimization.

Photovoltaic (PV) system is one of the promising renewable energy technologies. Although the ener... more Photovoltaic (PV) system is one of the promising renewable energy technologies. Although the energy conversion efficiency of the system is still low, but it has the advantage that the operating cost is free, very low maintenance and pollution-free. Maximum power point tracking (MPPT) is a significant part of PV systems. This paper presents a novel intelligent MPPT controller for PV systems. For the MPPT algorithm, an optimized fuzzy logic controller (FLC) using the Hopfield neural network is proposed. It utilizes an automatically tuned FLC membership function instead of the trial-and-error approach. The MPPT algorithm is implemented in a new variant of coupled inductor soft switching boost converter with high voltage gain to increase the converter output from the PV panel. The applied switching technique, which includes passive and active regenerative snubber circuits, reduces the insulated gate bipolar transistor switching losses. The proposed MPPT algorithm is implemented using the dSPACE DS1104 platform software on a DS1104 board controller. The prototype MPPT controller is tested using an agilent solar array simulator together with a 3 kW real PV panel. Experimental test results show that the proposed boost converter produces higher output voltages and gives better efficiency (90%) than the conventional boost converter with an RCD snubber, which gives 81% efficiency. The prototype MPPT controller is also found to be capable of tracking power from the 3 kW PV array about 2.4 times more than that without using the MPPT controller.

High-penetration renewable energy-based generators (REGs) in distribution systems have increased ... more High-penetration renewable energy-based generators (REGs) in distribution systems have increased the importance of impact assessment involving these systems. This assessment focuses on power quality (PQ) and compatibility between REGs and existing system components. Electric vehicle (EV) technology has also recently achieved a substantial market share. This technology requires the development of charging stations similar to current petroleum fuelling stations in the near future. Thus, the effect of EV stations (EVSs) on PQ must also be considered. This study presents a PQ analysis on the effects of high-penetration EVS and REG systems, including wind turbines, grid-connected photovoltaics (PVs), and fuel cell (FC) power generation units on a modified 16-bus distribution system under different loading and weather conditions. All data on EVS, wind farm, PV, and FC units as well as weather conditions presented in this paper were collected from different power companies and the Malaysian Meteorological Department. The system is modelled and simulated using the MATLAB/Simulink software to study the effects of these technologies on system performances at various penetration levels. Simulation results indicated that the presence of high-penetration EVSs and REGs can cause severe PQ problems such as frequency and voltage fluctuations, voltage drop, harmonic distortion and power factor reduction.

and sharing with colleagues.

Electric power systems research, Jan 1, 2004

A new approach to locate the voltage sag source using real current component Abstract Voltage sag... more A new approach to locate the voltage sag source using real current component Abstract Voltage sag can cause hours of downtime, substantial loss of product and also can attribute to malfunctions, instabilities and shorter lifetime of the load. Accurate voltage sag source location can help to minimize the loss and problems caused by voltage sag in a power distribution system. This paper proposes a new method to locate the source of voltage sag in a power distribution system. The proposed method uses the polarity of the real current component to determine the sag location relative to the monitoring point. The product of the RMS current and the power factor angle at the monitoring point is employed for the sag source location. A graph of this product against time is plotted. The voltage sag source location is determined by examining the polarity of the RMS current at the beginning of the sag. The proposed method has been verified by simulations and the results are proven to be in agreement when compared with the slope of system trajectory method.

Power Delivery, IEEE Transactions …, Jan 1, 2005

Available transfer capability assessment using evolutionary programming based capacity benefit margin

International Journal of Electrical …, Jan 1, 2006

The determination of ATC must accommodate a reasonable range of capacity benefit margin (CBM) so ... more The determination of ATC must accommodate a reasonable range of capacity benefit margin (CBM) so that the operation of power system is secure from the generation deficiency that may occur during a power transfer. There are two ways of incorporating CBM into ATC, which are by considering the CBM as firm and non-firm transfers. The CBM for each area is specified based on the installed generation capacity that gives the loss-of-load expectation index below 2.4 h/year. The determination of CBM based on heuristic search for a large ...

An intelligent load shedding scheme using neural networks and neuro-fuzzy

… Journal of Neural …, Jan 1, 2009

Load shedding is some of the essential requirement for maintaining security of modern power syste... more Load shedding is some of the essential requirement for maintaining security of modern power systems, particularly in competitive energy markets. This paper proposes an intelligent scheme for fast and accurate load shedding using neural networks for predicting the possible loss of load at the early stage and neuro-fuzzy for determining the amount of load shed in order to avoid a cascading outage. A large scale electrical power system has been considered to validate the performance of the proposed technique in determining the amount of load shed. The proposed techniques can provide tools for improving the reliability and continuity of power supply. This was confirmed by the results obtained in this research of which sample results are given in this paper.

Journal of Applied Sciences, Jan 1, 2006

Power Systems, IEEE …, Jan 1, 2008

The uncertainty of system operating conditions is a part of consequences which may cause to the v... more The uncertainty of system operating conditions is a part of consequences which may cause to the volatility of a transmission system. This will hinder the performance of transmission system to effectively transfer the power between areas. Therefore, accurate estimation of transmission reliability margin (TRM) is required to ensure effective power transfer between areas during the occurrence of uncertainties. The power transfer is also called as the available transfer capability (ATC) in which it is the information required by the utilities and marketers to instigate selling and buying the electric energy. The TRM is estimated by taking into account the uncertainties of line outages and system parameters generated by the bootstrap technique. A case study of Malaysia Power System is used to verify the robustness of bootstrap technique in the TRM determination. The results show that the combined impact of several uncertainties which significantly affect the value of TRM.

Transient stability assessment of a power system using PNN and LS-SVM methods

Journal of Applied Sciences, Jan 1, 2007

… and Drives Systems, …, Jan 1, 2005

Current trends of power quality monitoring LabVIEW or general programming languages such as C++. ... more Current trends of power quality monitoring LabVIEW or general programming languages such as C++. instruments are based on digital signal processors Examples of DSP based PQ monitoring instruments which (DSP), which are used to record waveforms and are commercially available are the Reliable Power Meter harmonics and comes with software for collecting data and PowerGuide4400. However, these instruments can only and viewing monitoring results. The variations in the record waveforms and use a software for collecting data and DSP based instruments are in the way algorithms that viewing monitoring results including voltage profiles and are developed for processing the real-time power harmonic distortion information. quality waveforms. At present, all of the available power quality monitoring instruments are not capable To implement an intelligent PQ monitoring instrument, of troubleshooting and diagnosing power quality which can process raw measurement data and provide problems. Therefore, a DSP-based power quality useful information for PQ diagnosis, a new DSP-based PQ monitoring instrument is proposed for real-time monitoring instrument is proposed. The instrument is based disturbance recognition and source detection. The on DSP because digital signal processors are distinct from proposed instrument uses the Texas Instruments the general-purpose microprocessor in terms of having a far TMS32OC6711DSP starter kit with a TI ADS8364EVM higher computing power. Furthermore, its architecture is analog digital converter mounted on the daughter card. wired for mathematical functions rather than general

Journal of Applied Sciences …, Jan 1, 2007

This paper presents transient stability assessment of electrical power system using probabilistic... more This paper presents transient stability assessment of electrical power system using probabilistic neural network (PNN) and principle component analysis. Transient stability of a power system is first determined based on the generator relative rotor angles obtained from time domain simulation outputs. Simulations were carried out on the IEEE 9-bus test system considering three phase faults on the system. The data collected from the time domain simulations are then used as inputs to the PNN in which PNN is used as a classifier to determine whether the power system is stable or unstable. To verify the effectiveness of the proposed PNN method, it is compared with the multi layer perceptron neural network. Results show that the PNN gives faster and more accurate transient stability assessment compared to the multi layer perceptron neural network in terms of classification results.

Harmonic source location at the point of common coupling based on voltage magnitude

TENCON 2004. 2004 …, Jan 1, 2004

Abstract This paper proposes a new method to locate the source of harmonic either from the utilit... more Abstract This paper proposes a new method to locate the source of harmonic either from the utility or the customer from measurement made at the point of common coupling (PCC). The proposed method is called&amp;amp;amp;quot; voltage magnitude comparison method&amp;amp;amp;quot; because it compares the measured harmonic voltage at the PCC and the calculated voltage either at the utility side or at the customer side in the Thevenin equivalent circuit. The calculated voltage magnitude which is greater than the measured voltage at the PCC is considered as the ...

A new method of transient stability assessment in power systems using LS-SVM

Research and Development …, Jan 1, 2007

Abstract--This paper presents transient stability assessment of electrical power system using lea... more Abstract--This paper presents transient stability assessment of electrical power system using least squares support vector machine (LS-SVM) and principle component analysis. Transient stability of a power system is first determined based on the generator relative rotor angles ...

A Systematic Approach In Estimating the Generator Parameters

… Power Components and …, Jan 1, 2002

One of the growing needs in transmission planning is to provide accurate sim-ulation models of th... more One of the growing needs in transmission planning is to provide accurate sim-ulation models of the generator, excitation system, and governor; however, the degree of accuracy of the generator model is often questioned because model pa-rameters currently used may have ...