特高压直流分层接入方式下受端换流母线电压稳定裕度分析

Study on the Voltage Stability Margin Index of the Receiving End Converter Buses Under UHVDC Hierarchical Connection Mode

为了保证新型特高压直流分层接入方式下的电压静态稳定,基于阻抗匹配理论研究了特高压分层接入方式下受端各换流母线的电压稳定裕度。首先,采用电网节点阻抗矩阵和多端口网络等值方法,将分层接入方式下的直流从其落点处等值成两个相对独立单端口网络的形式;进而,利用阻抗匹配定理,推导了分层接入方式下直流在各层换流母线电压稳定裕度的计算表达式;然后,研究了虚拟电压源、虚拟阻抗和虚拟功率的直流等值方案,分析了3种等值方案下所提出电压稳定裕度指标的差异性。最后,以实际锡盟–泰州±800 k V直流输电工程电网数据计算了等值方案下23节点的电压稳定裕度为29.1%,12节点电压稳定裕度为47.5%,算例结果验证了该电压稳定裕度指标在评估换流母线电压稳定性上的可行性。

A new the voltage stability margin index of each converter buses is studied in the UHVDC with hierarchical connection mode. Based on the node impedance matrix of the power network and the equivalent method of multi-port network, the hierarchical HVDC is equivalent to two independent single-port networks. By using the impedance matching theorem, DC voltage stability margin for each layer is derived. Furthermore, different virtual voltage source, the virtual impedance and the virtual power equivalent schemes are proposed. Finally, the feasibility of the voltage stability margin index is verified under ±800 k V Ximeng-Taizhou HVDC. The results show that the voltage stability margin of 23 nodes under this equivalent circuit is 29.1%, and the voltage stability margin of 12 nodes is 47.5%.