Research On Control Strategy Of Parallel Active Filter Based On Sliding Mode Control

The harmonic pollution of power system caused by the widespread application of power electronic equipment is becoming more and more serious,because the active power filter(APF)has the characteristics of good dynamic performance and obvious compensation effect,it is of great significance to improve the power grid environment.therefore,the research of APF has been a hot topic for scientists at home and abroad.This paper first analyzes the harm of harmonics,based on the working principle of APF,it is classified,the mathematical model of parallel APF is given.In order to improve the compensation ability of APF and ultimately improve the overall power quality,the harmonic detection and suppression are studied.In terms of detection methods,in this paper,the mathematical models of the p—q detection method and i_p—i_q detection method based on instantaneous reactive power theory are established,and the theoretical analysis and detection performance comparison are carried out,the calculation results show that the i_p—i_q detection method has better dynamic response and higher detection accuracy,which is suitable for the parallel APF studied in this paper.In the harmonic suppression method,the conventional sliding mode control method has the advantages of flexible modal design,strong robustness and simple physical structure,but in the application process,there are some defects,such as slow response speed,low accuracy,chattering and so on.In this paper,a sliding mode control method based on exponential reaching law for parallel APF is proposed,this method not only keeps the advantages of the common sliding mode control method,but also effectively improves the disadvantages of the common sliding mode control method,effectively reduces the chattering,so that the application effect of this method in APF of power system is improved.In the voltage outer loop,the PI control method is studied and analyzed,aiming at the shortcomings of PI control,a fuzzy adaptive PI control method is proposed,compared with PI control,this method has faster response speed,smaller overshoot and stronger robustness.Finally,the whole system simulation model of APF is built in MATLAB simulation environment.The simulation results show that the proposed sliding mode control method has better compensation effect,and the data show that the total distortion rate of harmonic current is reduced by 0.5%.Compared with the PI control method,the fuzzy adaptive PI control method proposed in this paper reduces the time for DC voltage to reach steady state by 0.02s.