Research on Key Technology and Equipment for Zhangbei 500kV DC Grid

With the capacity of new energy resources such as wind power and photovoltaic in Zhangbei region increasing rapidly, the reliable transmission and consumption capabilities of large-scale and high-proportion new energy resources are urgently improved. Considering the advantages of the VSC-HVDC transmission technology, Zhangbei project is designed as symmetrical bipolar system which adopts half-bridge modular multi-level converter (MMC) topology and overhead lines for power transmission. In this paper, a system scheme is presented, and some results are provided. Meanwhile, a novel modular cascaded hybrid DC breaker concept is proposed, and 500kV VSC valve and DC breaker prototype are developed to meet the requirement of the Zhangbei four-terminal dc grid.