基于线路阻抗短时调节的多直流连锁换相失败抑制方法

连锁换相失败是交直流混联电网的新型连锁故障形式之一。结合连锁关系在换相失败相关现象中的体现和参与环节,文中提出了一种在关键线路短时调节阻抗以降低耦合的抑制策略,重点讨论了策略的实施位置。在加权网络模型的基础上,基于直流分群界定了换相失败的连锁范围。在直流群内搜索对直流耦合关系影响较大的关键路径,并采用潮流介数比较各线路阻抗变化对系统运行状态的冲击,以避免在重要线路采取措施。针对不同的扰动,利用换相电压时间面积判断需要启动策略的直流群,从而实现有差别的连锁换相失败抑制。在修改的IEEE 39节点系统和某省市电网算例中,利用PSCAD/EMTDC开展仿真,结果均验证了关键线路阻抗短时调节策略抑制连锁换相失败的效率和有效性。

Suppression Method of Cascading Commutation Failure in Multi-infeed HVDC System Based on Temporary Impedance Regulation of Transmission Lines

The cascading commutation failure is one of the new forms of cascading failures in AC/DC hybrid power grid. Based on the reflection and the participation of the cascading patterns in the typical phenomena relevant to commutation failures, this paper proposes a suppression strategy to reduce coupling by temporarily regulating the impedance of the critical transmission lines. The discussion is emphasized on the location selection to implement the proposed strategy. Based on the weighted graphic network model, the scope within which the commutation failures tend to cascade is firstly obtained by high voltage direct current (HVDC) clustering. After that, the critical path with the relatively-large influence on the HVDC coupling relationship in a given HVDC cluster is searched. Then the power flow betweenness is applied to compare the impacts on the system operation status in the case that the impedance of different lines is changed. Thereby taking measures on the important lines is avoided. Meanwhile, the voltage-time commutation area is employed to determine the exact HVDC cluster where the proposed strategy should be launched. Hence the differentiating suppression of the cascading commutation failures is implemented. Simulations on the modified IEEE 39-bus system and a regional grid of China are carried out in PSCAD/EMTDC, and the results validate the efficiency and feasibility of the proposed strategy of regulating the impedance on the critical lines to prevent the cascading commutation failures.