送端系统机群摆动对直流功率恢复特性影响研究

Study on Impacts of Generator Cluster Swing in Sending-End Grid on DC Recovery Characteristics

近年来,我国交直流混联电网发展初具规模,电网安全稳定特性发生深刻变化,大容量特高压直流输电系统与传统交流电网的交互影响、耦合特性进一步复杂化。该文重点研究送端电网机群摇摆对近区特高压直流功率恢复特性的影响,发现当直流故障激发送端机群振荡后,随着系统戴维南等值电势幅值不断下降,直流换流母线电压跌落将造成直流功率在恢复过程中再次出现塌陷,对交流输电通道形成二次冲击,影响交流薄弱断面输电能力。最后基于实际电网算例,分析受端电网单永故障下多回直流同时发生相继换相失败故障对送端电网稳定性的影响。研究结论可为电网运行人员合理安排运行方式提供依据,有利于保障大区互联电网安全稳定运行。

In recent years, hybrid AC/DC power grid in China begins to take shape, and security and stability characteristics of power systems undergo profound changes. Besides, interaction and coupling characteristics between large capacity UHVDC transmission lines and AC power grids become more complex. The paper firstly studies impacts of generator swing in sending-end grid on DC power recovery characteristics, indicating that when some faults stimulate generator cluster swing and lead to DC bus voltage drop, the DC power in recovery process will collapse. Secondly, based on actual example, an analysis of generator cluster swing under multi DC lines commutation failure occurring at the same time due to single permanent fault in receiving end grid is put forward. The drop degree of DC power after commutation failure elimination is analyzed, and the impact of secondary disturbance caused by DC power drop on AC power grid and transmission capacity of important weak cross section is discussed. Conclusions of this paper provides reference for power grid operators to reasonably arrange operation mode, and helps to ensure safe and stable operation of power grid.