A Parallel Control Strategy for Power Mismatch Elimination of Photovoltaic Grid-Connected Cascaded H-Bridge Multilevel Inverter

The cascaded H-bridge (CHB) multilevel inverter is considered as one of the most suitable configurations for large-scale photovoltaic (PV) plants. However, power mismatch problem will easily happen when solar irradiation is uneven. The current work on power mismatch elimination focuses predominantly on voltage regulation, which cannot cope with severe power imbalance scenarios. In order to address this problem, in this paper, a parallel control strategy is proposed to eliminate power mismatch by power sharing between inverters. Since the power mismatch elimination strategy changes from voltage regulation to circulating current regulation, it can accommodate most imbalance cases without voltage overmodulation. Simulation results validated the effectiveness of the proposed strategy.