Mechanism and Risk Areas of Cascading Faults: A Newly Emerging Fault Type in Large-Scale Hybrid AC/DC Power Grids

摘要

With the rapid development of High-Voltage Direct Current (HVDC) systems, control and protection of hybrid AC/DC power grids have been faced with major challenges. Cascading fault which is a new fault type appearing as a result of a DC or a severe inverter AC fault in Line-Commutated Converter (LCC) -based HVDC systems is one of them. In this paper, first, the commutation failure, as main cause of cascading fault resulting from inverter AC fault, is described. Subsequently, the process and risk areas of the cascading fault incident are analyzed using PSCAD/EMTDC software. The simulation results demonstrate how the power flow transfer from the HVDC line to its parallel AC line, which is due to the blocking of the HVDC converter during the fault, shuts down the inverter AC system. Finally, in spite of the available commutation failure prevention approaches which only inhibit the power outages resulting from inverter AC fault, some feasible solutions for prevention of the power outages created by DC fault or inverter AC fault are pointed out.