Decoupled Modulation Scheme for Modular Multilevel Converters in Medium-Voltage Applications

Ensuring a good voltage waveform for the modular multilevel converter (MMC) is always of great importance. This article reveals that the modulation harmonic features of MMC would be adversely affected when applying circulating current suppression control. This problem becomes more severe in medium-voltage MMCs which has small number of submodules. A straightforward decoupled modulation scheme is proposed in this article to overcome this problem. Effectiveness of the proposed scheme is verified by simulation and experimental results.