直流闭锁后系统暂态稳定紧急协同控制策略研究

交流故障引发的电网换相换流器型高压直流输电在短时间内多次换相失败将导致直流闭锁，严重威胁故障后系统的安全稳定运行。提出了考虑直流闭锁过程的多直流功率支援和送端切机的紧急协同控制策略，以保障故障后系统的暂态稳定。首先，基于相轨迹首摆过程中斜率变化特性，定义了紧急控制投入判据，并推导出所需控制量与控制投入时刻、系统惯性等参数的解析表达式。其次，建立了可提供控制量与直流参与功率支援条数和送端切机台数的数学关系，并基于故障后稳定平衡点变化特性，确定了直流参与功率支援顺序以及送端切机顺序。最后，搭建了改进的IEEE 68节点交直流混联系统机电-电磁混合仿真模型，验证了所提策略的正确性和有效性。

Collaborative emergency control strategy of system transient stability after DC blocking

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).