Stability and dynamic analysis of doubly-fed variable speed pump turbine governing system based on Hopf bifurcation theory

Abstract

The stability of a doubly-fed variable speed pump-turbine governing system (VSPTGS) under the condition of small power disturbance was investigated. First, a novel model of the VSPTGS in turbine mode and pump mode is proposed based on the electromechanical transient model of the doubly-fed induction generator (DFIG). Then, the algebraic stability criteria of the system in turbine mode and pump mode are derived using Hopf bifurcation theory. Furthermore, the stability domain of the speed controller parameters is obtained when the power controller parameters are determined, and the dynamic behavior of the system is analyzed using bifurcation diagrams and numerical simulation. Finally, the power controller parameters are varied to study the influence of these parameters on the stability domain. The results show that Hopf bifurcation of a VSPTGS is subcritical. When the parameters of the power controller are fixed, the stability domain in pump mode is larger than that in turbine mode. The stability in turbine mode only depends on the speed controller parameters, whereas the stability in pump mode depends on both the speed controller parameters and the power controller parameters.