Research Into Control Strategy For Single-phase Shunt Active Power Filter

With rapid development of power electronic technology,a large number of harmonic sources,such as nonlinear devices and power electronic devices,are used in industrial production and daily life;thus,the harmonic pollution problem in power grid is caused and becoming more and more serious.Harmonic pollution not only affects the efficiency of power generation equipment and transmission losses,but also causes power quality decline.Compared to passive power filter,active power filter has good harmonic dynamic performance and compensation accuracy,and there is no resonance phenomenon;therefore,active power filter is recognized as the most effective device for harmonics elimination.In this paper,single-phase shunt active power filter has been selected as the research object,and several key technologies that affect the compensation performance of shunt active power filter are studied,such as harmonic detection,instruction current tracking control,and the stability control of DC-side capacitor voltage.Firstly,against problems of the fast Fourier transform and sliding window discrete Fourier transform detection method,such as large computation amount and long delay time,the single-phase circuit harmonic current detection method based on single-phase circuit ip-iq algorithm has been adopted,which has high detection accuracy and good dynamic performance.In analyses of instruction current tracking control strategies,the triangle wave comparison control strategy has the disadvantage that frequency affects its response speed.Therefore,the hysteresis current control strategy with fast response speed and good anti-jamming performance has been decided based on selecting appropriate hysteresis controller bandwidth.Secondly,against the problem that DC-side capacitor voltage is hard to balance the shunt active power filter power loss and compensation performance when the grid voltage fluctuates,the control strategy: droop control is presented to optimize the set value of DC-side capacitor voltage.Based on the conventional PI control strategy and combining the fuzzy controller design principle,a novel fuzzy adaptive PI control strategy with good dynamic performance and strong robustness is designed.Considering that commonly used of the stable control strategy of DC-side capacitor voltage has the disadvantages of slow response and power loss and so on,a droop-fuzzy adaptive PI control strategy is proposed.When the grid voltage fluctuates,the droop controller can be employed to optimize the set value of DC-side capacitor voltage,and fuzzy adaptive PI controller can be employed to realize the tracking control of the set value.Finally,simulations and experiments are conducted based on Matlab/Simulink simulation software and experiment platform,the simulation and experiment results indicate that the harmonic current detection method based on single-phase circuit ip-iq algorithm has better detection performance,and the hysteresis current control strategy has better tracking performance;and in Comparison with the traditional PI control strategy,the obtained DC-side capacitor voltage has less overshoot and more robustness based on the proposed droop-fuzzy adaptive PI control strategy,even the harmonic distortion rate of the compensated power grid current is reduced from3.34% to 2.44%.