Design Method of Split Capacitance Value of ANPC Half Bridge Photovoltaic(PV) Submodule

Cascaded H-bridge converter and modular multilevel converter (MMC) are suitable for large-scale photovoltaic (PV) grid connected system, because they can realize PV DC modular distributed access. In order to adapt to the 1500V PV voltage access and achieve electrical isolation, the PV sub-module adopts the DAB structure of active neutral point clamp (ANPC) half-bridge on the PV side and H-bridge on the output side. The split capacitor of ANPC side can buffer the high-frequency current generated by DAB modulation, and reduce the impact on PV voltage due to the interference of sub-module capacitor harmonic of grid connected converters on DAB transmission power. In this paper, the voltage fluctuations of PV and ANPC split capacitor are analyzed, and a design method of the split capacitance value is proposed. The proposed design method is validated using time-domain simulations via PSCAD/EMTDC on a 200kW PV submodule.