Neutral Point Clamped MOSFET Inverter With Full-Bridge Configuration for Nonisolated Grid-Tied Photovoltaic System

摘要

Existing nonisolated full-bridge neutral point clamped (NPC) inverters for a single-phase grid-tied photovoltaic (PV) system have limitations such as shoot-through and low European Union (EU) efficiency. In order to address these limitations, an NPC superjunction MOSFET nonisolated inverter with full-bridge configuration (NIIFBC) is proposed in this paper. This inverter reduces the possibility of shoot-through, thereby improving the reliability of the grid-tied PV system. It controls the grid current by energizing two coupled inductors individually during positive and negative half-grid cycles. This obviates the possibility of reverse recovery loss in switches due to their body diodes. Furthermore, two external silicon carbide diodes of a clamping branch cause negligible reverse recovery loss in switches besides a constant common-mode voltage. Therefore, the main claims of NIIFBC are low leakage current, high EU efficiency, and reliability. A generalized leakage current model for the proposed inverter is developed. In order to validate the veracity of the model and the claims of NIIFBC, a 1-kW prototype is designed and developed. The experimental results of NIIFBC validate the claims made by the authors. Its performance comparison with the existing nonisolated full-bridge inverters is given. Furthermore, a variant circuit of NIIFBC operating at nonunity power factor is proposed.