Continuous commutation failures of line-commutated converter-high voltage direct current (LCC-HVDC) caused by AC faults over a short period will lead to DC blocking, which seriously threatens the safe and stable operation of the post-fault power system. A collaborative emergency control strategy of multi-DC power support and generator-tripping at the sending-end, one which considers the DC blocking process, is presented to ensure the transient stability of the post-fault power system. First, a control enabling criterion is defined based on the variation characteristics of phase trajectory slope during the first swing. Then the analytical equation between needed control quantity, control enabling time and system inertia is derived. Second, the mathematical relations between the supplied control quantity and the number of DC lines participating in power support and generators participating in generator-tripping at the sending-end are deduced. The participation sequence and generator-tripping sequence are determined on the basis of the variation characteristics of the post-fault stable equilibrium points. Finally, an electromechanical-electromagnetic simulation model of the improved IEEE 68-bus AC/DC hybrid power system is employed to verify the correctness and effectiveness of the proposed collaborative emergency control strategy.

This work is supported by the Integration Project of National Natural Science Foundation of China (No. u22B6006).