Suppression Strategy of Capacitor Voltage Fluctuation of MMC Based on Second Harmonic Injection

Abstract

In order to reduce the capacitance of the sub-module of modular multilevel converter (MMC), it is necessary to suppress the fluctuation of the capacitor voltage, thereby reducing the size and cost of the MMC. In order to realize the lightness of MMC, this article proposes a double-frequency circulation injection strategy. First, it analyzes the characteristics of sub-module capacitor voltage ripple after double-frequency circulation injection; Then the parameters of the injection are derived in detail; Finally, the strategy proposed is simulated and verified on the PSCAD platform, and the results show that the proposed strategy can well suppress the capacitance voltage ripple of the sub-module.