Optimized Device Loss and Capacitor Voltage Reduction of MMC-HVDC for Offshore Wind Farms

Device loss and submodule capacitor voltage fluctuations are two important factors that decide the cost and efficiency of MMC-HVDC connected offshore wind farms. In this paper, the impact of discontinuous pulse width modulation (DPWM) with circulating current injection (CCI) method on reducing the device loss and capacitor voltage fluctuations is investigated. It is demonstrated that DPWM with different CCI method can achieve minimum device loss and minimum capacitor fluctuations, respectively. Simulation and experimental results show the effect of DPWM with CCI in the operation of the MMCs and the efficacy of the method compared to conventional modulation techniques.