Leakage Current Suppression for Dual-DC-Port DC–AC Converter in PV-Battery Hybrid System

Since the high efficiency and low cost of single-stage power conversion, dual-dc-port dc-ac converters have been used in photovoltaic (PV)-battery hybrid systems. However, achieving leakage current suppression in this configuration is challenging due to its coupling characteristics in terms of common mode voltage (CMV) reduction and power distribution. To deal with this issue, a method using unbalanced large, medium, small vector modulation (ULMSVM) with CMV transition reduction is proposed in this paper. Firstly, the CMV of voltage vectors is calculated and sorted under different voltage conditions. Then, for the purpose to reduce CMV transition, the switching interval between vectors is at most one vector in a switching sequence according to sorting relations. In addition, high CMV small vector sequences and medium vector sequences can be used as independent power control sequences to help achieving battery charging and discharging. Finally, to realize flexible power regulation, a new power control scheme is proposed to balance the PV power fluctuation by the battery power exchanged, which can provide the discharge/charge sequences with different control capabilities. The effectiveness of the proposed method is verified by the experiment at the end of the paper.