Circulating Current Analysis and Power Mismatch Elimination Strategy for an MMC-Based Photovoltaic System

This paper analyzes the current circulation mechanism of a large-scale photovoltaic (PV) grid-connected power generation system based on modular multilevel converter (MMC) under different solar irradiation. In MMC based PV system, each submodule is connected to PV arrays through a dc-dc converter, so power mismatch problem will easily happen when solar irradiation is uneven. Based on the circulating current analyzes, a power mismatch elimination strategy based on capacitor voltage deviation is proposed, which greatly reduces the circulating current of the system when the irradiance is uneven. Simulation results proved the correctness of the analysis and the effectiveness of the proposed strategy.