Research of new scheme of adaptive overvoltage protection in hybrid AC/DC grid

Aiming atproblem of absence of effective coordinationbetween AC side overvoltage protection and DC controlstrategy andtaking DC system single pole blocking leadingabrupt power reduction as example, this paper analyzes filter action strategy and change rate of active and reactive power respectively after single pole blocking failure. Then a new principle of an adaptive AC overvoltage protection is put forward. With single pole blocking in DC system, considering equipment insulation level, the proposed scheme can adaptively adjust overvoltage protection time settings without changing original protection characteristics. It can slid over filter clearing time and prevent load loss caused byAC overvoltage protectionaction. When overvoltage is caused by AC grid disturbance, it can operate correctly according to original logic andensure equipmentsafety. Simulation results show that this new scheme canstrengthen protective relay coordination between AC and DC systems, and thus of great importance in improving hybrid system stability.