An analytical method suitable for revealing the instability mechanism of power electronics dominated power systems

摘要

In view of the instability phenomenon of power electronics dominated power systems, an analytical method suitable for revealing the instability mechanism of power electronics dominated power systems is proposed. The proposed analytical method divides power electronics dominated power systems into two subsystems: electrical subsystem and control subsystem. First, the weak links of the system are screened out by eigenvalue analytical method, then the linearized relation of state variables in the weak links is derived from the perspective of the electrical subsystem. Through the study of the interactions between the weak links of the electrical subsystem and the related control subsystem, the mechanism of the system instability can be explained by "positive feedback effect" formed by the interactions between the electrical subsystem and the control subsystem. The proposed analytical method can reveal the dynamic interactive process of state variables compared to impedance analytical method and eigenvalue analytical method when the system is unstable. Meanwhile, a linearized model of weak links in the electrical subsystem can be set up specially, helping to reduce the workload. Finally, the analytical method is verified by three study cases when VSC-HVDC is connected to the weak AC power grid under two different operation conditions and when direct-drive permanent magnet synchronous generator system is connected to VSC-HVDC system.