Research on Transmission Scheme of Large-scale Renewable Energy Transmitted Through Series Hybrid DC System

In order to realize the collection and long-distance transmission of large-scale renewable energy in the "Three North" and southwest regions of China, two renewable energy transmission schemes through series hybrid DC system are proposed, including renewable energy island transmission and grid connection transmission. The series hybrid DC system adopts the hybrid structure of line commutated converter (LCC) and modular multilevel converter (MMC), which can make full use of the advantages of LCC and MMC. The paper presents the operation control strategy of hybrid DC system under two operation modes, and designs the startup strategy of hybrid DC system under different operation modes at the sending end. Finally, a simulation model is established in PSCAD/EMTDC to verify the feasibility of the transmission schemes and the effectiveness of the control strategy.