Frequency Control Strategy Of Wind Turbine Under Different Operating Status

With the development of wind power,control of variable speed wind turbines(VSWT)to participate system frequency control has become a new requirement for grid development.But the weak inertia of VSWTs makes it difficult for wind power outp.u.t to respond to changes in system frequency.The volatility of VSWTs makes it more difficult to select the frequency control strategy and controller parameter.The frequency control method focuses on the additional control at a given wind speed.Hence,the frequency stability of the power system with large-scale wind turbines has been a severe challenge.Therefore,the research of this thesis on frequency control strategy of wind turbine under different operating status is important significance and practical value.The main contributions of this thesis are summarized below:(1)The frequency control strategies are divided into no-limited power control strategy and limited power control strategy in the thesis.Four improved frequency control methods are proposed.The available frequency capability is quantified under all operating status.The method to select the frequency controller parameter values is proposed.The frequency control effect of no-limited power control strategies are compared in the same system.(2)The synthetic frequency response model considering the VSWTs participating system frequency control is proposed in the thesis.In this model,the influence of synchronous machine control parameters,equivalent system parameters and wind power penetration on system frequency response is analyzed.A multi-objective function for evaluating the system frequency control effect quantitatively is proposed.The selection mechanism of optimal controller parameters using genetic algorithm is established.The test in the equivalent model of actual system verifies the method of optimizing frequency controller parameter to be correct.(3)On this basis,a wind farm frequency control method is proposed to control the wind turbines considering the operating status.The scheme of wind farm coordination frequency control is further proposed.The frequency control effect and effectiveness of coordinated control scheme is verified.