| With the large-scale integration of renewable energy represented by wind power into the power grid,the intermittence and fluctuation of its power generation mode increase the difficulty of power system scheduling,and the safety and stability of the power grid operation are seriously threatened.Moreover,the wind turbine is connected to the power grid through power electronic devices,and the speed is decoupled from the system frequency,so it does not have inertia.Although it has a certain frequency response capability under the control of the existing control method,the frequency regulation output power of wind turbine is not stable considering its power generation affected by natural conditions,which brings problems to the system frequency stability.Therefore,the study of wind power frequency modulation technology is an inevitable requirement of power grid development.Therefore,this paper focuses on the collaborative control strategy of wind farm participating in primary frequency regulation of power system.The main work is as follows:(1)Aiming at the problems of wind farm participating in primary frequency regulation of power system without energy storage,a double-layer control method for wind farm was proposed,which divided primary frequency regulation control into station-layer control and equipment-layer control.The station-layer controller considers the dynamic process of wind turbine in the frequency regulation process and uses the model predictive control method to optimize the power distribution of wind turbine.The equipment-layer controller takes the control results of the station layer as reference and adopts the distributed Newton method with super linear convergence to correct the unreasonable control results caused by prediction error and wind turbine model error.The effectiveness of the double-layer control method is verified by actual data.Compared with the traditional method,the synchronous frequency characteristics of wind farms are better,and the power distribution between wind turbines is more reasonable.(2)Aiming at the problem of wind farm with energy storage participating in primary frequency regulation control of power system,a double-layer control method for combined wind turbine-energy storage system was proposed.Considering the prediction error of system frequency,the model predictive control method is used to optimize frequency regulation coefficient of the wind turbine and energy storage.According to the prediction error and real-time speed state of wind turbine,the equipment-layer controller adopts the rotor speed adaptive control and prediction error adaptive control methods based on the prediction error coefficient and rotor speed coefficient to correct the unreasonable control results caused by wind turbine state prediction error.The effectiveness of the double-layer control method is verified by the actual data.Compared with the traditional method,it has stronger ability to deal with the frequency prediction error and better synchronous frequency characteristics.Moreover,it has better ability to deal with wind speed prediction error,and the power distribution among wind turbines and energy storage is more reasonable.(3)Aiming at the problem of rotor speed recovery of wind turbine in wind farm,a double-layer control method for rotor speed recovery of wind turbines was proposed.Firstly,the recovery process of wind turbines’ rotor speed is divided into the process of rotor speed decline and rotor speed rise,and the overall power characteristics of the wind farm are set well.Then,in order to ensure the overall power characteristics of the wind farm and consider the dynamic characteristics of the fan in the process of speed recovery,the station-layer controller adopts the model predictive control method to optimize wind turbines power.Then,in view of the unreasonable control results caused by wind turbines’ prediction error,the controller of the equipment layer adopts the adaptive control method to correct the unreasonable control results in real time.Finally,the effectiveness of the double-layer control method is verified by simulation.Compared with the traditional method,not only wind turbines can recover to the ideal speed in the final stage,but also the external power characteristics of the wind farm are more ideal,which can prevent the secondary drop of the system frequency. |
