连接弱交流系统的高压直流换流站无功补偿协调控制策略

在馈入端交流系统强度较弱、直流传输功率频繁波动的高压直流系统中,换流站无功补偿设备的协调控制对改善换流母线电压的稳定性具有重要意义。提出了一种基于静态同步补偿器(STATCOM)和电容器组相互协调的多模式协调控制策略,主要包括换流母线电压无静差跟踪额定电压的稳态调压模式、换流站参与近区交流系统电压调节的自动电压控制(AVC)模式,以及换流母线发生短路故障时抑制电压波动与换相失败的暂态控制模式。基于实际工程参数,在电磁暂态仿真软件(PSCAD)建立了±800kV酒泉—湖南特高压直流输电系统仿真模型,并在直流功率波动、AVC中心下发指令电压和馈入交流系统短路故障等多种工况下对该多模式控制策略的性能进行了仿真验证。仿真结果论证了所提出的换流站无功补偿设备协调控制策略的合理性和有效性。

Coordinated Control Strategy of Reactive Compensation for HVDC Converter Station Connected to Weak AC System

Coordinated control of reactive power compensation is essential to the stability of bus voltage in high voltage direct current(HVDC)connected to weak AC system and characterized with frequent power fluctuation. Based on the coordination of the static synchronous compensator and fixed capacitors, a multi-mode control strategy is proposed, including the steady-state voltage regulation mode, the automatic voltage control(AVC)mode and the transient control mode. In the steady voltage regulation mode, the converter bus voltage can be controlled at its rated value with zero steady-state error by the coordinated control of the static synchronous compensator(STATCOM)and capacitor bank, while the reactive component devices of the HVDC converter will participate in the voltage regulation of nearby power grid in the AVC mode, and the transient control mode is created for mitigating voltage fluctuation and reducing the probability of commutation failure during grid fault period. Besides, according to the actual parameters of the ±800 kV DC power transmission project from Jiuquan to Hunan, a model is established. Then, different working conditions, such as DC power fluctuation, operation complying with the AVC commands and short-circuit accident are carried out. The correctness and effectiveness of the proposed control strategy are verified by the simulation results. This work is supported by National Natural Science Foundation of China(No. 51477044)and State Grid Corporation of China(No. 5216A015001S).