Research On Harmonic Detection And Control Of Shunt Active Power Filter

With the rapid development of modern industrial technology and the wide application of power electronic technology,all kinds of rectifiers,frequency converters and nonlinear loads are increasing day by day,which produce a large number of harmonic currents to the power grid and seriously threaten the security and stability of the power system.Active power filter(APF)has gradually become one of the main measures to solve the harmonic pollution of power grid because of its advantages of real-time compensation,flexible control and high reliability.Taking shunt active power filter(SAPF)as the research object,this paper studies the key control strategies of SAPF,such as harmonic current detection,current tracking control algorithm and capacitor voltage control strategy.This paper focuses on the most widely used harmonic current detection algorithm based on instantaneous reactive power theory,and analyzes and compares the advantages and disadvantages of p-q harmonic current detection method based on instantaneous reactive power theory and i_p-i_q harmonic current detection method.Finally,this paper uses i_p-i_q harmonic current detection method based on instantaneous reactive power theory to track and detect power grid harmonics in real time.The advantages and disadvantages of traditional hysteresis control and triangle wave comparison control are compared.Based on the research of the traditional hysteresis current control method and voltage vector control technology,the improved space vector hysteresis control method is adopted to solve the problem of redundant switching action in the control process caused by the neutral point offset in the traditional hysteresis control system,which leads to the high switching frequency.The model is built on the MATLAB/Simulink simulation platform to verify it.The simulation results show that the total harmonic distortion(THD)of the improved space vector hysteresis algorithm is low,and the improved hysteresis space vector current tracking algorithm is superior to the triangle wave comparison method and the basic hysteresis comparison method.In this paper,the algorithm model of three-phase three wire SAPF based on i_p-i_q harmonic current detection method and improved hysteresis space vector harmonic current tracking method is established.The DC side voltage control is optimized.The traditional PI control algorithm and optimized PI control algorithm are analyzed and summarized.The analysis results show that the improved PI control algorithm has fast dynamic response speed and low total harmonic distortion rate,The thd is reduced from 4.62%to 3.83%,which verifies the effectiveness of the control algorithm.