Small Disturbance Stability Limit Dynamically Dominated by Phase-Locked Loop of Doubly-Fed Wind Turbine
Aiming at the problem of small disturbance stability of grid-connected doubly-fed wind farms dynamically dominated by phase-locked loop,a method for determining small disturbance instability of doubly-fed wind farms is proposed.Firstly,a second-order linearization model of a single doubly-fed wind turbine is established.Secondly,the derived second-order linearization model is extended to grid-connected doubly-fed wind farms based on the single-machine equivalence model.Finally,the small disturbance stability limit of grid-connected doubly-fed wind farms dynamically dominated by phase-locked loop is derived based on the Rausch-Hurwitz theorem which explains the influence law and the intrinsic mechanism of active output of wind turbines,grid connection strength,phase-locked loop control parameters and the number of wind turbines on the small disturbance stability of grid-connected doubly-fed wind farms dynamically dominated by phase-locked loop.The results show that the small disturbance stability of the system is adversely affected by the increase of active output,the weakening of system connection strength and the inappropriate set-ting of the control parameters.A grid-connected doubly-fed wind farm consisted of 15 doubly-fed wind turbines is used to verify the correctness and effectiveness of the small disturbance stability limit proposed,and it is not necessary to set up a full-order model of the wind farm,which reduces the amount of calculation.
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