高压直流输电系统低功率运行的无功控制策略

当高压直流输电系统低功率运行时,受换流站接入点谐波性能和交流滤波器设备性能限制,投入的交流滤波器提供的无功功率在满足站内无功消耗外可能仍有大量剩余,导致大量剩余无功送入交流系统,使得换流站及附近厂站的电压容易偏高,继而影响到电网的安全稳定运行。文中提出一种充分利用换流器自身无功调节能力的换流站无功控制策略,该策略在有功输送不受影响的前提下,以直流电压为控制量,以换流站无功交换量为反馈量,通过改变直流电压参考值来对换流器的无功消耗进行定量控制,可有效抑制换流站过剩无功对交流系统电压的影响。该无功控制策略解决了现有直流工程中低功率无功优化功能由于开环控制无法对无功功率进行精确控制的问题。PSCAD/EMTDC和实时数字仿真器(RTDS)中的仿真结果验证了该方法的正确性和鲁棒性。

Reactive Power Control Strategy for Low Power Operation of HVDC Transmission System

When the HVDC transmission system is in low power operation, restricted by the PCC harmonic performance of converters and the AC filter equipment performance, the surplus of reactive power provided by the AC filter may still be tremendous apart from meeting the reactive power consumption of converters. This will lead to the interchange of enormous surplus reactive power between the converter and the AC system, making the voltage of the converter station and nearby substations to become high and then affect safe and stable operation of power grids. By utilizing converter reactive power regulation capability, a kind of reactive power control strategy is proposed, in which the DC voltage is used as control variable and reactive power exchange capacity of converter station as feedback variable. The strategy changes the converter reactive power consumption by changing the reference value of inverter side voltage to effectively suppress the AC system voltage fluctuations without influencing active power transmission. The reactive power control strategy can overcome some disadvantages of low load reactive power optimization function that just cannot accurately control the reactive power because of its open-loop control. The simulation results in PSCAD/EMTDC and RTDS verify the correctness and robustness of the proposed method.