Compared to half-bridge based MMCs, full-bridge based systems have the advantage of blocking dc fault, but at the expense of increased power semiconductors and power losses. In view of the relationships among ac/dc voltages and currents in full-bridge based MMC with the negative voltage state, this paper provides a detailed analysis on the link between capacitor voltage variation and the maximum modulation index. A hybrid MMC, consisting of mixed half-bridge and full-bridge circuits to combine their respective advantages is investigated in terms of its pre-charging process and transient dc fault ride-through capability. Simulation and experiment results demonstrate the feasibility and validity of the proposed strategy for a full-bridge based MMC and the hybrid MMC.
- capacitor voltage ripple
- modular multilevel converter
- DC fault
- hybrid power systems
Zeng, R., Xu, L., Yao, L., & Morrow, D. J. (2015). Pre-charging and DC fault ride-through of hybrid MMC based HVDC systems. IEEE Transactions on Power Delivery. https://doi.org/10.1109/TPWRD.2014.2360042