Applied Mechanics and Materials Vol. 785

Abstract: This paper reviews neural network control algorithm for power quality improvement. Further, this paper focuses on the neural network control algorithm for DSTATCOM and surveys its area of improvements. Various architectures of Neural Network such as Adaline/Widrow-Hoff, perceptron, Back-propagation (BP), Hopfield, and Radial Basis Function (RBF) that has been reviewed in this paper. It is found that many researches on theoretical works and single phase system are widely performed, whereas its application on distribution network for three phase system is hardly found. Even so much improvement that have been done by researchers theoretically to improve the drawbacks of Neural Network controller; there are still wide gaps for verification through experimental implementation and industrial applications.

Abstract: This paper was conducted in order to identify and classify the different types of Power Quality Disturbances (PQD) based on a new approach the Analysis Of Variance (ANOVA). ANOVA is used as feature selection for the PQD parameters. The datum of PQD from the PSCAD/EMTDC^® simulation and Power Quality Monitoring has been validated before feature extraction analysis can be commenced. The obtained datum is then analyzed by using Windowing Technique (WT) based on Continuous S-Transform (CST) to extract the features and its characteristics. Moreover, the study focuses an important issue concerning the identification of PQD selection, detection and classification. The feature and characteristics of three types of signal such as sag, swell, and transient signal are obtained. The outcome of the analysis shows that a new approach framework ANOVA-Based Before and After Neural Network (NN) classification has a slightly increases to 15-25% in term of classification of PQD.

Abstract: Power quality is becoming a concern in modern electrical network due to complexity of the system. To improve power quality, there needs to be analysis and research on complex power quality events systematically. Disturbances in distribution system, including sag/swell, transient, harmonic, voltage notch, and flicker that affect power quality are simulated in this research work. The comprehensive set of models are developed in PSCAD with minimum blocks and settings without compromising the essence of power quality events. This research work aims to introduce the power quality events to electrical engineering students, as well as reinforce understanding of power quality disturbances in distribution system through interactive simulation approach.

Abstract: A new adaptive power system harmonic estimator is presented, which is competent of tracking power system harmonic components. The proposed estimator technique is based on the normalized Least Mean Square (LMS), which is a stochastic gradient descent algorithm. The learning method of the proposed estimator is based upon the recursive estimate of the signal power, and is faster tracking of harmonic components as compared to the introduced Adaptive Linear Element (ADALINE).

Abstract: The degradation of polymer insulation is affected by many factors. One of the main factors is surface discharge. In this work, the characteristics of surface discharge on different types of polymer insulation material under different types of electrode shapes were studied. The insulation materials used were high density polyethylene (HDPE), low density polyethylene (LDPE) and polypropylene (PP). Different types of electrode shape used were sharp, flat and sphere electrodes. From the experiments that have been performed, surface discharge characteristics were found to be influenced by the type of insulation material and the electrode shape. Hence, a better understanding on the characteristics of surface discharges may be attained.

Abstract: Interconnection of Distributed Generation (DG) in distribution system presents many potential benefits as well as drawbacks. The impacts of DG might vary with the types of generator. This paper presents a study on the impacts of synchronous DG's interconnection in distribution system. Steady state analysis is carried out to analyze the impact of DG on voltage profile and short circuit current considering before and after DG interconnection. Dynamic analysis is also performed for investigating the performance of DG when a part of distribution system is being islanded. Results show that the penetration of DG contributes to the changes of power flow in the system, hence give impacts to the overall system performance.

Abstract: Due to the complexity of power system nowadays, voltage limit has become a concerned issue. This phenomenon attracted numerous studies in finding the ultimate solution. This paper presents the development of self-tuning technique for identifying maximum loadability for selected buses in a power system network. The algorithm is able to perform fast process in consideration of the voltage limit between 0.9 p.u. to 1.05 p.u. as the acceptable voltage limit in power system community. The proposed concept is conducted for single and multi-load increment; executed on IEEE 14-Bus RTS and IEEE 26-Bus RTS. The proposed technique is feasible for larger transmission system implementation, which in turn avoid computation burden to power system operators.

Abstract: Many power tracing techniques have been developed but are limited to the application of transmission service pricing in a deregulated environment. To expand the knowledge of power tracing theory and its application, this paper adopts the power tracing theory into voltage stability improvement. This paper proposes a modified novel line stability factor index with load tracing capability known as LQP_LT for the purpose of finding the appropriate locations in a power system network for any preventive and corrective actions. Unlike the commonly applied real power tracing, this method presents the reactive power tracing utilizing the proportional sharing method (PSM) with all the line reactive losses being taken into consideration in the network study with the system size remain the same. IEEE 5 bus system is used to demonstrate the LQP_LT concept and all the results obtained are compared with modified Fast Voltage Stability Index with load tracing ability (FVSI_LT). The results obtained found to be efficient in determining the reactive power contributed by a certain load bus in a transmission line which ultimately responsible to cause a stressed line and overall voltage instability in a system.

Abstract: Utilization of photovoltaic power plants on distribution system has been widely used in many countries. Commonly, the photovoltaic system has been injected to the distribution system and called as photovoltaic distributed generations (PVDG) through medium or low voltage levels. The injection of the PVDG on the distribution system has been claimed to improve the voltage profile and reduce power losses. However, the good performance of the distribution system in term of the steady-state point of view, cannot directly guarantee to give a good response during the system disturbed. Therefore, to show the impact of the PVDG injection on power system stability is concerned in this paper. The size of the power injection and location of the injection site that have been determined by using the optimization technique, are then analyzed based on three scenarios, each of which represents the PVDG injection of 2x0.5MW, 4x0.5MW, and 6x0.5MW respectively at different bus locations. The voltage-, frequency-, and rotor angle-stabilities are analyzed to show the dynamic impact of the PVDG during three-phase fault condition. The analysis results indicate that the second scenario gives the best response in term of the rotor angle-, frequency-, and voltage-responses during dynamic conditions which supplies active power around 28.78% of the total load. The PVDG injection power in the first scenario (14.39% of total load) and also in the third scenario (43.18% of total load) would result in rotor angle and frequency responses with more oscillations being compared to the second scenario. However, the system dynamic responses for all scenarios show damped oscillations to reach the steady-state conditions.

Abstract: Power delivered to consumer from utilities is susceptible to power quality problems. The most common power quality problems are voltage sag. Modern equipment nowadays are prone to problems associated with voltage sag. Such problems can be apprehended by several mitigation methods. This paper will discuss voltage sag mitigation method by eliminating the injection transformer in ordinary Dynamic Voltage Restorer (DVR) and applying Single Phase Matrix Converter (SPMC) in a single phase DVR topologies. The objective of this paper is to investigate the potential mitigation method without the injection transformer in the DVR topology. DVR circuit will be constructed and simulated using MATLAB/SIMULINK software. It is hoped that the result of this work will provide a simpler mitigation technique where existing DVR topology can be constructed with less component that provides unnecessary losses in the DVR itself.Index Terms—Injection Transformer, DVR, SPMC, MATLAB/SIMULINK.