A Novel Cascaded Multilevel Inverter Topology and Its Control Strategy for Medium-Voltage Direct-Mounted Photovoltaic Grid-Connected System

With the increase of the inverter voltage and power, the cascaded multilevel inverter (CMI) becomes an emerging solution owing to its modularity. The output voltage of CMI could be a reasonably high level to mount the medium-voltage grid without transformers directly. Many structures of CMI have been studied in recent years but can not achieve power balance. To realize multi-channel maximum power point tracking (MPPT) and balance the power among H-bridges (HBs) in the three phases, a novel three-stage CMI topology and its control strategy are proposed in this paper. Experiment results proved the effectiveness of the proposed topology and its control strategy.