Wind Power Curtailment Control With Constraint Of Power Variation Rate During The Rotor Speed Recovery

The large-scale wind power integration not only aggravate the power fluctuation in the system,but also weaken the frequency regulation capability of conventional generators,which challenges the frequency security of the power system.In order to deal with this problem,wind turbines should no longer to treat maximizing wind energy capture as a single goal,but consider the impact on grid frequency to integrate to power system friendly.In this context,wind turbines are required to participate in the Automatic Generation Control(AGC)of the power system,which is of great significance to ensure the safe and stable operation of the power system.After the wind speed increases,the wind turbine unit will switch to constant power operation.In response to the AGC command of the power grid,wind turbines need to curtail output power to maintain constant through the speed control and pitch control.However,when the wind speed is not high enough,the finite aerodynamic power cannot support the wind turbines to maintain constant power output in accordance with the AGC power command,so it will switch to the rotor speed recovery,operating according to the optimal power curve for stability.When the wind speed is high enough,wind turbines will switch to constant power operation.It is found in this paper that during the rotor speed recovery,the unbalanced power caused by the change of the output power will cause the phenomenon of power system frequency peak,which adversely affect the safety and stability of the power system.In order to solve this problem,this paper carried out the following work:(1)By analyzing the influence mechanism of wind power fluctuations on power grid frequency,this paper reveals the main cause of the power system frequency peak phenomenon during the rotor speed recovery--the excessive wind power variation rate,and further summarizes the influence patterns of the variation rate of wind power on the power system frequency during the rotor speed recovery.(2)For solving the problem of power system frequency peak during the rotor speed recovery,the wind power curtailment control is proposed based on the idea of constraining power variation rate.This strategy can adjust the constraint of the wind power variation rate according to the level of output power,and make the wind turbines smoothly switch from the operation mode of optimal power curve to the operation mode of maintaining the constant power on the premise of minimizing the power loss during the rotor speed recovery.(3)Simulating the wind power curtailment control based on the idea of constraining power variation rate with the model built on Matlab/Simulink and FAST software.And the experiment is further completed based on the test platform of power system with synchronous machine simulator,wind turbine simulator and feedback load.Simulation and experimental results verify the feasibility and effectiveness of the proposed control strategy.