797 / 2019-04-29 11:46:32

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

Cascading Faults,Commutation Failure,Hybrid AC/DC Grids

With the rapid development of High-Voltage Direct-Current (HVDC) transmission technology, control and protection of hybrid AC/DC power grids have been faced with major challenges. Cascading fault caused by a DC or a severe inverter AC fault in Line-Commutated Converters (LCC) -based HVDC systems is one of them which seriously jeopardizes the operation of large-scale hybrid AC/DC power grids. 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, results in a blackout in the inverter AC side. Finally, in spite of the available commutation failure prevention approaches which only inhibit the blackout resulting from inverter AC faults, some feasible solutions to prevent the blackout caused by either DC or inverter AC faults are pointed out.