Research on multi-frequency current tracking control of three-phase grid-connected VSI

This paper proposes a multi-frequency current tracking control method which can be applied in the application of APF(Active Power Filter), programmable current source etc. Because the method based on the stationary PI inner loop and the dq outer loop can´t be used in the case of high frequency, a new method is proposed. The proposed method includes a stationary PI inner loop and an Amplitude-Phase outer loop, which can realize separate control of each harmonic in each phase precisely in a wide frequency range, and keep the advantages of the stationary PI method: the anti-interference ability, low harmonic distortion in the line current, fast response speed and simple control. The parameter design method of both loops is also described. At last, simulation results based on PSCAD/EMTDC and experimental results are given to prove the feasibility of this method.