Control method of doubly fed wind turbine for wind speed variation based on dynamic constraints of reactive power

Abstract

With the development of large wind farms, the voltage problem caused by the power changes of wind farms occurs continuously because of the wind speed variation. The problem cannot be resolved by extra reactive power compensation because of the limitations in cooperation and response speed. A doubly fed induction generator (DFIG) possesses the power decoupling control capability, which can be used to prevent the voltage change rapidly. However, the dynamic processes of the power demands of the grid and the power limits of the DFIG have not been considered. Therefore, a vector equivalent model of the DFIG considering the controllability of the rotor voltage is established. The feasible power ranges that are limited by the electromagnetic process and controller response are deduced. The dynamic requirement and limitation of the reactive power under the wind speed variation are investigated. The emergency control strategy of reactive power contributed by the DFIG is proposed on the basis of the requirement and limitation. The simulation shows that the rapid adjustment capability of the DFIG can be fully utilised by the proposed method.