Experimental Verification of Three-phase PV Inverter Using Multiple Bidirectional Choppers for Utility-scale PV Systems

This paper presents a three-phase inverter for utility-scale photovoltaic (PV) systems using multiple cascaded bidirectional choppers and a three-phase transformer with a three-legged core. The negative terminal of the PV panels and the ground are directly connected and the common zero-sequence current flows in each phase current. As a result, the inverter can achieve boost function and it can accept a wide range of dc input voltages. Furthermore, no high-frequency harmonic current flows in the stray capacitance of the PV panels, which makes the parallel operation of the inverters easier. The operating principles and control method of the inverter are discussed and the validity of the control method is verified by conducting experiments using the 1.7 kW downscaled model.