Research on Coordination Control Strategy of LCC-MMC Hybrid HVDC Transmission System under Fault

Abstract

High voltage direct current based on modular multilevel converter (MMC-HVDC) has a good application prospect in engineering, but it is expensive and cannot handle DC faults and other disadvantages. So it is still not suitable for long-distance transmission. To solve these problems, this paper designs multi-terminal hybrid DC transmission system with a line commutated converter based on the rectifier side (LCC) and a modular multilevel converter based on the inverter side (MMC). Besides, for the asymmetric fault on the AC side of the system, the minimum trigger angle control strategy based on the rectifier side LCC and the maximum modulation ratio control strategy based on the inverter side MMC are proposed to improve the DC system transmission power and reduce the possibility of power transmission interruption. Finally, a model of hybrid DC transmission is built in PSCAD/EMTDC, the proposed strategy is verified its effectiveness.