Loss Characteristics of Modular Multilevel Converter with RC-IGBT for High Voltage DC Transmission

The modular multilevel DC/DC converter, intended for realizing interconnection of DC grids with different voltage levels, is one of the key equipment in DC grids. The fully controlled power device is the core device of the high voltage DC/DC converter, which determines the performance of the convertor system. Compared to the traditional IGBT module, the reverse-conducting IGBT (RC-IGBT) has lower thermal resistance and higher current tolerance with the same package. By controlling the desaturated characteristic of the body diode through the gate of RC-IGBT, the reverse recovery loss can be reduced. In this paper, RC-IGBT is applied to the high voltage MMC DC/DC converter, and a method of desaturated control is proposed to reduce the loss of the converter. The gate desaturation control characteristic of RC-IGBT diode is studied, and the working principle of the sub-module of MMC DC/DC converter is analyzed, and the pulse distribution states of RC-IGBT MMC DC/DC converter are given. The strategy of saturation control based on RC-IGBT sub-module is proposed. Finally, the MATLAB / Simulink software is used to prove the validity of the design, and the loss calculation of the simulation model is carried out. The simulation and calculation results show the effectiveness of the proposed desaturation control method.