A novel strategy of the midpoint potential control for three level APF

This paper is to make the LCL three-level active power filter (APF) have a more stable midpoint potential balanced ability and better harmonic compensating performance. The novel midpoint potential modulated strategy that modulating-wave is injected into the zero sequence voltage is studied and the disadvantages of this method in the harmonic compensation are pointed out. Aiming at the problem that the zero sequence voltage component increases the distortion rate of the network side current, a new algorithm of midpoint potential balance based on LCL three -level APF is proposed. In this algorithm one low pass filter (LPF) is introduced to filter the zero sequence voltage component in order to reduce its influence on the compensation current and the designed parameters of the LPF are given. At last, the simulation and experimental results show that the proposed algorithm can significantly improve the compensation performance of the three-level APF and verify the feasibility of the proposed algorithm.