多分层直流馈入的特高压环网开断运行特性及安控措施

某受端省级电网的特高压交流环网投运后，为多特高压直流分层接入、满功率消纳提供了条件，受端特高压交直流以及1000 kV/500 kV交流电网之间的耦合强度加大。为保证故障后特高压交直流电网的可靠运行，仿真分析了1000 kV特高压环网开断后交直流耦合的电压稳定特性，以及开断后大功率转移至500 kV电网的热稳定特性，分析了此电网结构下电压稳定、热稳定两大运行问题产生的原因；为减小防控措施量，计及直流调制、切负荷等多资源控制手段的灵敏度以及优先级，建立了防控两大运行问题的统一多资源协控优化模型，并提出了基于控制代价的恒步长梯度下降启发式寻优方法来求解得到协控措施。依托实际电网开展了仿真计算，验证了该控制措施能够有效减少防控措施量。

Operation Characteristics and Security Control Measures of UHV Loop Network with Multi-Hierarchical DC Infeed after Breaking

The operation of a provincial UHV AC loop network provides conditions for hierarchical access and full power accommodation of multiple UHV DC systems, and also increases the coupling strength between UHV AC and UHV DC, and between 1000 kV/500 kV AC power grids at the receiving end. To ensure the reliable operation of UHV AC/DC power grids after line fault occurs, simulation is used to analyze the voltage stability characteristics of the coupled AC and DC systems after breaking of the 1000 kV UHV loop network, and the thermal stability characteristics of the power system when large power transfers to the 500 kV power grid after breaking, and the causes for voltage stability and thermo-stability problems are studied. In order to reduce the amount of security control measures, a unified multi-resource co-control optimization model is established for controlling the two operational problems, with consideration of the sensitivity and priority of multiple control methods such as DC modulation and load shedding. And a control-cost-based heuristic optimization method of constant-step gradient descent is proposed to obtain the co-control measures. It is verified through simulation of an actual power grid that the proposed controlling method can effectively reduce the amount of prevention and control measures.