Analysis and Protection of Converter-Side AC Faults in a Cascaded Converter-Based MVDC Link: ANGLE-DC Project

Medium-voltage direct-current (MVDC) technology exhibits advantages over ac transmission due to its enhanced capacity, controllability, and flexibility. A practical example is the ANGLE-DC project from Scottish Power Energy Networks, which converts existing 33 kV circuits into dc operation improve system capacity in North Wales, U.K. Specially designed cascaded power converters are employed build up ±27 link voltage. Within converter stations, converter-side single-phase faults may threaten safe of converters. This paper presents an analysis such for MVDC based on ANGLE-DC. It shown that capacitors will be overcharged without suitable protection place. strategy using a bypass thyristor-based branch presented relieve overvoltage issues following faults, it verified through simulations conducted PSCAD/EMTDC. For completeness, case studies considering post-fault also included.