Study Of Series Power Quality Compensator (SPQC) With Current Feedback Control Strategy

Series power quality compensator (SPQC) is a power electronic equipment designed to mitigate voltage disturbances in forms of voltage sags, voltage swells, and voltage harmonics. The SPQC injects series voltage to eliminate the voltage disturbances by combining series voltage sourced inverters(VSI) with a dc-link capacitor and a shunt rectifier. The theory and control strategy are discussed at detail and a design of diagnosis tool for SPQC is represented.First, compensation theory and detection method of SPQC are discussed at detail. And running conditions of SPQC are analyzed and based on it, capacity formulas are induced.In view that the validity and the effectiveness of the SPQC depend on the accuracy and the dynamic behavior of the control strategies adopted, the study of the control strategy is the emphasis of the paper. In order to analyze control strategies, a basic model of the SPQC is set up by adopting the state-space averaging method. And the behavior of VSIs and the rectifier is expressed in differential equation forms. Based on the state-space averaging model of the SPQC, the transfer function and the block diagram of the exiting open-loop control strategy for VSIs are represented. There is error existing inevitably due to the existence the inductance and the resistance of the series filter and the series transformer. One plan to mitigate the error is to include inner feedback loops. And in order to regulate the voltage across the dc-link capacitor, a proportional-plus-integral control strategy for the rectifier is discussed.Then, the design of a fault diagnosis system combing ANN and expert system is represented at detail.Simulation results and experimental results on SPQC verify the validity and the effectiveness of the control strategy.