Impact of virtual inertia control of DFIG wind turbines on system small-signal stability

Doubly-fed induction generator (DFIG) wind turbines with virtual inertia control considered and the power system are coupled to each other on dynamic characteristic. Since the control input of virtual inertia is affected by the tracking ability of phase-locked loop (PLL), the impact of DFIG wind turbines considering virtual inertia control under the action of PLL on system small-signal stability has become a problem demanding prompt solution. First, by taking into account the transient characteristics of rotor voltage, PLL, virtual inertia control, rotor side converter and mechanical part of DFIG wind turbines, an interconnected power system model of DFIG considering PLL and virtual inertia control is created. Then, as both PLL and virtual inertia control will affect the oscillation modes of synchronous generators, the impacts of PLL and virtual inertia control on power system small-signal stability are explored theoretically by analytic method. The results show that the damping ratio of power system is affected by the participation factor of virtual inertia influenced by PLL. Besides, the smaller the PI parameter of PLL is, the smaller the participation factor of virtual inertia is, and the bigger the damping ratio of electromechanical oscillation will be. This is opposite to the impact of DFIG without considering virtual inertia control under the action of PLL on system stability. The rationality of the interconnected power system model and correctness of analysis results have been verified by simulation. © 2016 Automation of Electric Power Systems Press.