Alleviation of Leakage Current and Neutral Point Voltage Deviation for Using an Eight-Switch Inverter

Due to the less number of switching devices, a coupled eight-switch converter is an attractive topology for reducing cost in photovoltaic generation systems. Nevertheless, the medium vectors are absent in an eight-switch converter compared to the conventional three-level topology, resulting in an undesired performance for leakage current suppression and neutral point voltage (NPV) balancing with existing methods. To overcome such limitations, this article proposes a modulation method without the medium vectors for leakage current suppression and NPV balancing for eight-switch converters. In order to mitigate the leakage current, except for using the low common-mode voltage (CMV) vectors to reduce the amplitude of the CMV, two pairs of sequences are further designed to lower the transitions of the CMV. Simultaneously, the average switching frequency is reduced and the NPV balance can be achieved by changing between sequences. The effectiveness of the proposed method is verified by simulations and experiments.