含调相机的高压直流送端换流站无功协调控制策略研究

HVDC Converter Station Reactive Power Coordinated Control Strategy With Synchronous Condenser

暂稳态电压越限是影响高压直流送端电网安全稳定运行的重要因素。通过开展换流站暂态过电压及事故后稳态电压的特性研究,在分析静态无功补偿设备动作特点和调相机性能特点的基础上,针对配置了新一代调相机的高压直流送端系统,以抑制送端电网暂态过电压、减小事故后稳态电压越限水平以及减少换流变分接开关动作次数为目标,制定换流站无功协调控制策略,即:调相机采用定无功控制,直流小功率时运行在进相状态,大功率时运行在滞相状态,代替站内部分交流滤波器投入;交流滤波器采用定交流电压控制,换流站无功适当过补,直流大功率时代替部分交流系统无功补偿装置。对某实际特高压直流系统的机电仿真结果表明,所提协调控制策略有效抑制了故障时的暂态过电压,改善了事故后稳态电压水平,同时减少了直流功率变化时换流变分接开关的动作次数。

Overvoltage of steady or transient states by the faults is a serious issue that affects the safe and stable operation of the HVDC transmission network.In this paper,the characteristics of the transient overvoltage and the steady-state voltage after the accidents in the converter station are studied.Based on the analysis of the operating characteristics of static reactive power compensation equipment and the performance characteristics of the synchronous condenser,the reactive power coordination control strategy is formulated with the aim of suppressing the transient overvoltage at the sending end power grid,reducing the steady-state voltage over-limit level after the accidents,and lowering the number of times of the converter transformer tap switch.The strategy is:The synchronous condenser is operated in constant reactive power control,which is running in phase-in mode when the power of HVDC is low and in phase-lag mode when the power is high,replacing some of the AC filter inputs.The AC filter is operated in constant voltage control,in which,the AC filter provides parts of reactive power to compensate the AC line with high-power.The electromechanical simulation results of an actual HVDC system show that the coordinated control strategy can effectively suppress the transient overvoltage during the faults and improve the steady-state voltage level after the accidents,reducing the number of actions of the converter tap when the DC power changes.