Three-phase multilevel inverter with reduced number of active power semiconductor switches for solar PV modules

This paper presents a three-phase switched-battery multilevel (SBM) inverter for solar photovoltaic (PV) applications. The proposed inverter requires less number of power MOSFETs and gate drivers, and therefore, it is expected to be more compact and reliable than the conventional cascaded H-bridge multilevel (CHBM) inverter. For example, sixty units of power MOSFETs are required to construct a three-phase 11-level CHBM inverter, whilst a SBM inverter with the same number of levels needs only 27 units. The switching losses of the SBM inverter are expected to be lower than that in conventional PWM-controlled inverters because the power MOSFETs in the SBM inverter are switched at a much lower frequency. In addition, the proposed inverter has an integrated charge mode operation which is very suitable for solar PV applications. The performance of an 11-level SBM inverter has been evaluated using PSIM software and the simulation results confirm that the proposed inverter is capable of producing low total harmonic distortion (THD) AC voltages without the need of bulky filters.