改善多馈入直流系统电压无功特性的直流控制策略

DC control for improving voltage and reactive power characteristics of multi-infeed HVDC system

为了改善多馈入直流系统受端交流系统的电压无功综合特性,在直流系统逆变侧引入了定交流电压控制;然后,使用新型指标——电压稳定耦合因子来衡量直流输电子系统换流母线间的影响,并指导该控制方式在多馈入系统中的设置方案;同时,提出了一种平滑切换逻辑控制器,以实现直流系统在定交流电压控制和其他控制策略之间的平滑切换。针对三馈入直流输电系统的电磁暂态仿真结果说明,当受端交流系统发生严重故障时,该控制策略相比常规的定熄弧角控制,能够有效改善弱交流系统电压稳定性及直流系统间的不利相互作用。

The constant AC voltage control is applied to the inverter-side of multi-infeed HVDC system to improve the voltage and reactive power characteristics of its receiving-end AC system,and an index called the voltage stability interaction factor is proposed to measure the interaction among the commutation buses of its DC subsystem and to guide the configuration of control strategy in the multi-infeed HVDC system. A controller is designed to realize the smooth switchover between constant AC voltage control and other control strategy. The results of electromagnetic transient simulation for a three-infeed HVDC system show that,when serious fault occurs in the receiving-end AC system,the proposed constant AC voltage control may improve the voltage stability of weak AC system and reduce the adverse interaction between AC and DC systems more effectively than the constant extinction angle control.