The AC side fault characteristics and protection scheme of the unified power flow controller based on MMC

摘要

The Unified Power Flow Controller (UPFC) based on Modular Multilevel Converter (MMC) is one of the highly controllable flexible AC transmission system devices, which is more suitable for high-voltage and large-capacity transmission fields. The main circuit topology and operating principles of MMC-UPFC is presented in this paper. The fault characteristics of several typical faults and detailed protection configuration of AC side of MMC-UPFC are analyzed, considering the influence of valve control and protection. Along with discussing the overall AC side protective schemes, the focus of this paper has placed on the valve side AC bus differential protection, T-line differential protection and the series interfaced transformer differential protection. The simulation by RTDS is carried out and shows that the proposed protection scheme is feasible.