The Research On Voltage Sag Determination And Compensation Strategies For Distribution Power System

Voltage sag is the most important power issue, and dynamic voltage restorer (DVR) has been considered to be the most effective custom power device which alleviates voltage sags. In order to improve the real-time and accuracy of detection methods for voltage sag and ameliorate the economical efficiency of DVR, this paper mainly researches on the voltage sag detection method as well as the compensation strategy of DVR. The major contents of this paper are detailed as follows:The conventional magnitude-phase detection system based on three-phase software phase locked loop has a low speed of dynamic response affected by negative-sequence and harmonic components. Also it cannot exactly extract the foundational positive-sequence phase angle of a three-phase power system. This paper proposes a novel three-phase magnitude-phase detection method based on double synchronous reference frame. The proposed method can decouple the positive dq and negative dq sequences and detect the magnitudes/phases of foundational positive- and negative-sequence components of three-phase voltages. The simulation results verify that the proposed method has a high detecting precision and a good dynamic performance.According to different methods of energy extraction, DVRs could be classified as types: DVR with no energy storage (also named uninterrupted dynamic voltage restorer, UDVR) and DVR with energy storage. DC-link capacitor is the usual method of energy storage. This paper proposes an improved integrated compensation strategy for UDVR, and simulation results verify that the proposed strategy can alleviate phase jump compared voltage sags and the magnitude of injected voltage is low. On the other hand, this paper considers the compensation duration of DVR with DC-link capacitor and proposes the optimized time compensation strategy. The simulation results verify that DVRs which adopt the proposed strategy can obtain longer compensation duration than those which adopt minimize energy compensation strategy.This paper designs the software flowcharts of DVR based on TMS320F2812 DSP chip, which include AD sample, the decoupled double dq transform algorithm, compensation strategies and SVPWM algorithm.