Overview on resonance characteristics and resonance suppression strategy of multi-parallel photovoltaic inverters

Photovoltaic(PV) inverters have been widely used in large-scale PV power generation systems to reduce the system mismatch and increase the output power. With the increasing installed capacity of PV power stations, the number of string PV inverters increases, which brings about risk of inverter resonance and influences the quality and stability of multi-parallel inverters grid-connected system. Thus, the problems of multi-parallel inverters resonance have become a hot research topic. This paper is focused on the case of grid-connected string PV inverter systems, and the grid-connected PV inverter resonance where resonance suppression strategy will be analyzed and discussed. Firstly, the structure of string PV inverter and multi-parallel inverters system are presented. Secondly, discussions are made about the model of multi-parallel inverters system and its resonance characteristics based on the multi-input-multi-output(MIMO) system, Norton equivalent circuit and carrier synchronization. Thirdly, two strategies of “inverter level” and “system level” are provided to summarize the multi-parallel inverters resonance suppression strategy. Finally, the development tendency of resonance suppression strategy and conclusions are prospected.