Improving Quality of Electric Power Supply

Abstract

Power quality (PQ) has become an important issue in recent times for the customers, service suppliers and equipment manufacturers. The suppliers consider PQ from the system reliability and their competitiveness in the electricity market, the equipment manufacturers consider PQ because of its effects on the proper operations and the price of their equipment, whereas customers consider good PQ that ensures the normal operations of processes, and extends the lifespan of devices. In an attempt to better the power quality of supplies to satisfy customers' demand, installing custom power devices is considered as the most efficient method. This thesis concentrates on two most effective devices: Dynamic Voltage Restorer (DVR) and Static synchronous compensator (STATCOM). The DVR is a series connected device which can protect the sensitive load against some power quality disturbances. Unlike other researches in which DVR is controlled and designed for one or several functions, we focus on the design and control of DVR with multifunction, including voltage swell, voltage sag due to symmetrical and unsymmetrical short circuit, starting of motors, and voltage distortion. In this thesis, we present a new structure and propose two new control methods of multifunctional DVR for voltage quality correction. Simulation results show the superior capability of the proposed DVR to improve power quality under different operating conditions and the effectiveness of the proposed method in terms of efficiency, accuracy and fast response time. The STATCOM is known as an effective device which can regulate the voltage quickly, improve transient stability and compensate variable reactive power. The control method of STATCOM was presented in a number of publications, and therefore we focus on load flow analysis which studies the steady state of the power system network. The load flow analysis in the power system incorporating STATCOM is an important issue in power system analysis, power quality, power planning and system operating. For this task, we present a new approach which is an improvement of the Newton-Raphson algorithm. Results show that, the accuracy and the speed of computation are enhanced. Furthermore, a software called Load Flow Analysis which can analyze the power system with and without STATCOM is developed. This software is a useful tool for the teaching, learning and practicing purpose. It can help engineers and operators calculate the local power system in order to improve power quality, and to optimize the operation of the power system. The goal of the power system is to provide electrical energy for its customers an acceptable degree of quality. Therefore, reliability evaluation is one of the most important factors in designing and planning a distribution system. Unlike a transmission system, evaluating the reliability indices of a distribution system is more difficult because of the complexity of the operation status. To solve this problem, we improve the analytical technique, program and apply it to evaluate the reliability of the distribution system. Compare with Monte Carlo simulation, the proposed method is simple, flexible and fast. Therefore, it is suitable to apply for the distribution system.

Power quality (PQ) has become an important issue in recent times for the customers, service suppliers and equipment manufacturers. The suppliers consider PQ from the system reliability and their competitiveness in the electricity market, the equipment manufacturers consider PQ because of its effects on the proper operations and the price of their equipment, whereas customers consider good PQ that ensures the normal operations of processes, and extends the lifespan of devices. In an attempt to better the power quality of supplies to satisfy customers' demand, installing custom power devices is considered as the most efficient method. This thesis concentrates on two most effective devices: Dynamic Voltage Restorer (DVR) and Static synchronous compensator (STATCOM). The DVR is a series connected device which can protect the sensitive load against some power quality disturbances. Unlike other researches in which DVR is controlled and designed for one or several functions, we focus on the design and control of DVR with multifunction, including voltage swell, voltage sag due to symmetrical and unsymmetrical short circuit, starting of motors, and voltage distortion. In this thesis, we present a new structure and propose two new control methods of multifunctional DVR for voltage quality correction. Simulation results show the superior capability of the proposed DVR to improve power quality under different operating conditions and the effectiveness of the proposed method in terms of efficiency, accuracy and fast response time. The STATCOM is known as an effective device which can regulate the voltage quickly, improve transient stability and compensate variable reactive power. The control method of STATCOM was presented in a number of publications, and therefore we focus on load flow analysis which studies the steady state of the power system network. The load flow analysis in the power system incorporating STATCOM is an important issue in power system analysis, power quality, power planning and system operating. For this task, we present a new approach which is an improvement of the Newton-Raphson algorithm. Results show that, the accuracy and the speed of computation are enhanced. Furthermore, a software called Load Flow Analysis which can analyze the power system with and without STATCOM is developed. This software is a useful tool for the teaching, learning and practicing purpose. It can help engineers and operators calculate the local power system in order to improve power quality, and to optimize the operation of the power system. The goal of the power system is to provide electrical energy for its customers an acceptable degree of quality. Therefore, reliability evaluation is one of the most important factors in designing and planning a distribution system. Unlike a transmission system, evaluating the reliability indices of a distribution system is more difficult because of the complexity of the operation status. To solve this problem, we improve the analytical technique, program and apply it to evaluate the reliability of the distribution system. Compare with Monte Carlo simulation, the proposed method is simple, flexible and fast. Therefore, it is suitable to apply for the distribution system.