Loss calculation method of modular multilevel HVDC converters

The modular multilevel converter (MMC) is a novel voltage source converter (VSC) topology with great potential for high voltage direct current (HVDC) transmission applications. The MMC-based HVDC system has main characteristics of flexible controlled and low switching frequency so that its losses are smaller than that of the two-level VSC-based HVDC (VSC-HVDC) system. In this paper, the operating characteristics of MMC and its losses are analyzed, and a method is presented to calculate the on-state losses according to the different on-state current of upper and lower leg. Furthermore, after the impact of junction temperature coefficient in IGBT module, a method using curve fitting to calculate the switching losses of MMC is considered. Finally, the losses of MMC are calculated in MATLAB, and the corresponding loss reducing measures are obtained from the results which also show that the method proposed is reasonable and feasible.