A Grid-forming Control Method of Modular Multilevel Converter with Integrated Distributed Photovoltaic and Battery Energy Storage System

With the construction of large-scale photovoltaic (PV) stations, the capacity and voltage level of photovoltaic converters need to be improved. This paper presents a novel configuration of grid-connected PV system based on modular multilevel converter, which is capable of integrating multiple PV submodules (PVSM) and battery submodules (BSM). The dc side of PVSM and BSM is coupled, and all PVSMs operate at the maximum power point. A grid forming control is proposed for the converter, which can suppress the PV power fluctuation and provide frequency support for the grid using the energy in the BSMs. The circulating current suppression strategy is adopted to realize the energy balance of the converter and ensure the power quality of output voltage and current. The effectiveness and accuracy of the proposed control method are verified by the simulation results in PSCAD/EMTDC.