ENHANCING THE POWER QUALITY USING DYNAMIC VOLTAGE RESTORER (DVR)

With the developments of computer technology and power electronics, the conflicts between power-quality-sensitive loads and power quality contaminated instruments become more and more considerable, which make concentrated reflection on voltage sags. Custom power technology can provide good solutions for these problems in power distribution system. Among them, dynamic voltage restorer (DVR) is a novel series-connected power electronics device. By injecting compensation voltage, it can compensates for all kinds of dynamic power quality issues such as sags, swells and interruption, thereby enhancing the quality of power supplied to sensitive loads. The research object of this thesis is dynamic voltage restorer based on super capacitor. Through theoretic analysis, Matlab simulation and experiments, the voltage detection, compensation characteristics of DVR, wide-range electrical transformation and design of DVR are studied in this paper. A fast and accurate voltage detection method is the base of dynamic compensation. This paper proposes a novel voltage detection method, which is derivation transformation method. Analysis and simulation verify its accuracy and fast speed. In order to emphasize the influence of energy storage units on DVR’s compensation, this paper makes a comparison between DVRs with and without energy storage unit, and concludes that DVR should have an energy storage unit to make sure good compensation effect. Since the energy storage unit is necessary, the issue on its interface with power system is discussed, and a novel wide range electrical transformation system is proposed. Software simulation and hardware tests are implemented to verify the effectiveness of the proposed structure. Then, this paper presents the structure of DVR based on super capacitor energy storage, and system design and control of the DVR are studied in detail. Finally, a large number of digital simulations show that the proposed detection method and control strategy are effective.