A fast fault protection based on direction of bus-side capacitor discharge current for a high-surety power supply

A short-circuit fault protection strategy based on the direction of bus-side capacitor discharge current for a high-surety power supply, known as Super Uninterruptable Power Supply (Super UPS), is studied in this paper. It consists of multiple energy sources and storage components. All energy sources and storage components are connected to a common DC bus through converters in the system. If a short-circuit fault occurs in the DC port of any energy source or storage component including its converter, it will result in a rapid drop of the DC bus voltage. Therefore an effective fault protection strategy is necessary to keep the uninterruptable power for the critical load. In this paper, the characteristics of the short-circuit fault are analyzed first. Then, a fast short-circuit fault locating and isolating strategy based on the direction of the discharge current of the busside capacitors of the converters is proposed. Finally, the proposed protection strategy is verified by simulations.