Fault Protection In DC Distribution Systems Via Coordinated Control of Power Supply Converters and Bus Tie Switches

A new fault protection method responds to the current needs of emerging dc power distribution systems by coordinating electronic power converters and mechanical contactors to rapidly isolate short circuit faults while maintaining continuity of power to loads. This work is important because the increasing performance, higher efficiency, and decreasing cost of electronic power converters have spurred a rediscovery and proliferation of dc power distribution systems. Although dc distribution offers advantages such as higher transmission efficiency, higher power density, higher reliability, and ease of interfacing asynchronous sources, enthusiasm for adopting dc technologies suffers from widespread concern over the means to protect dc distribution systems against short-circuit faults. The developed fault protection method rapidly limits the fault current, de-energizes the main distribution bus, reconfigures the bus via mechanical contactors, and re-energizes the system. The entire process can be accomplished fast enough to comply with the requirements of CBEMA and IEEE standards on power quality. A fast and reliable fault detection method has been developed in order to coordinates power converters and contactors. With this method the source power converters independently enter into current-limiting mode as soon as they recognize a fault condition. The bus segmentizing contactors autonomously decide whether to open or not based on their local interpretation of time-to-trip curves as functions of apparent equivalent circuit resistance. This method allows converter and contactors to coordinate to provide fault protection for dc distribution systems independently on communication failures. Simulation and experimental results show that fault current can be limited within few milliseconds, faults can be isolated within 20 ms and that the system can be re-energized within 100 ms. Moreover, this work provides system design considerations and limitations on components and system parameters