Seok-Min Kim, Min-Gyo Jeong, Juyoung Kim, and Kyo-Beum Lee, "Hybrid Modulation Scheme for Switching Loss Reduction in a Modular Multilevel High-voltage Direct Current Converter," IEEE Transactions on Power Electronics, vol. 34, no. 4, pp. 3178–3191, Apr. > Paper

A modular multilevel converter (MMC) is regarded as a promising topology in high-voltage direct current systems. However, the

MMC consists of numerous submodules (SMs) and switching devices, which lead to a considerable switching loss, and increased

cost and size of the heat sink. To mitigate these issues, this paper presents a novel modulation method composed of

fundamental frequency modulation (FFM) and multicarrier-based sinusoidal pulsewidth modulation schemes. The main purpose of

this modulation method is the reduction of switching loss while maintaining good harmonic performance. However, the FFM scheme

leads to the unbalanced capacitor voltage of each SM in the MMC. Accordingly, this paper additionally proposes the rotation method

and selective voltage balancing control for SMs to ensure effective performance of the method. Simulation and experimental results

verify the effectiveness and performance of the proposed modulation scheme through switching loss and spectral analyses.