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. This work is supported by National Natural Science Foundation of China(No. 51277193)

National Basic Research Program of China(973 program)(No. 2012CB215206)

and Fundamental Research Funds for the Central Universities(No. 2014ZZD02).