Current-fed Z-source converter for medium-voltage medium-frequency isolated solar-photovoltaic systems

Solar-photovoltaic (PV) is a fast growing renewable energy source. For its a abundance and maturity, utility scale PV farms are getting integrated to electrical systems in many countries. For PV energy integration to grid, bulky line frequency transformers are used to meet isolation requirements. This work proposes a medium-frequency (MF) isolated PV system for medium-voltage (MV) utility scale applications, based on current fed Z-source inverter (CZSI) and a cascaded multilevel inverter for MV side. The proposed PV system uses a common magnetic MF link for isolation and a CZSI for low voltage boost in a single stage enhancing efficiency as well as individual maximum power point tracking (MPPT). CZSI offers natural overlap protection in H-bridge and a filtered input current which enhance sensing for MPPT algorithm. Design equations for the CZSI, simulations and experimental validation are presented.