Continuous Operation of Wind Power Plants Under Pole-to-Ground Fault in an HVDC System Consisting of Half-Bridge MMCs and Disconnecting Switches

This article focuses on a multicircuit HVDC system which can localize the dc line fault without dc circuit breakers. The conventional fault clearing method causes the shutdown and the restart of the wind power plants, which results in the suspension of the power supply. The suspension may affect the balance of supply and demand, and may cause frequency drop in the onshore ac power system. To solve the problem, this article proposes a system switching method to enable the continuous operation of the wind power plants under the dc line fault. The proposed method utilizes the half-bridge modular multilevel converter to clear the fault while keeping the wind power plants operating. As a result, the proposed method realizes the continuous operation of wind power plants and shorten the transmission outage to 0.2 s. Thus, it greatly increases the supply reliability. Experimental results demonstrate the validity of the proposed method.