Abstract：Modular multilevel converter based HVDC (MMC-HVDC) is a new generation VSC-HVDC topology invented by Siemens. The problem of voltage balancing among the submodules (SM) is difficult to solve. The traditional method, which uses the sorting results of the SM capacitor voltages and fires the IGBTs directly, leads to relatively higher power losses. This paper proposes an improved voltage balancing control method, which reduces the switching operation significantly and the switching losses of the converter decreases consequently. The model of MMC-HVDC with 20 SMs is realized by PSCAD/EMTDC, and the traditional and improved voltage balancing control methods are compared. The simulation results demonstrate that the model is reasonable and the improved method is effective.
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2011, Vol. 26 
