Design and Application of Distributed Energy Dissipation Device in LCC-MMC Transmission System

Line commutate converter – modular multilevel converter (LCC-MMC) hybrid high voltage direct current (HVDC) system combines the advantages of both LCC-HVDC and MMC-HVDC, and will be wildly used in the future. The sub-module will withstand a very high voltage if a fault occurs in MMC converter station. In order to reduce this voltage, the LCC converter must operation in inversion state through gate-shift (GS) control strategy as quickly as possible. Normally, the fault signal was sent to LCC station through communication and GS control strategy was triggered due to this signal. Even though, the time lag between fault time and GS triggering time is as long as 60ms. In this long time lag, the sub_module (SM) voltage will be charged up to 4270V, which is very danger for IGBT. The solution of distributed dissipation resistor installed in SM is proposed in this paper and recommended values were also given out. Simulation works based on PSCAD are conducted to verify this method. The simulation results show that the proposed solution is valid.