Research Of Wind-Storage Frequency Regulation Control Based On Hybrid Energy Storage System

Under the energy strategy of sustainable development,wind energy has been greatly developed as a renewable clean energy.The frequency regulation ability of the system is reduced because that the original part of the conventional generator in the power system is out of operation with large scale wind turbines incorporated into the power grid.Therefore,improving the frequency modulation ability of the wind power system,so that it can provide frequency regulation assistance to the power grid like the conventional generator,has become active.In this thesis,firstly,the DFIG wind turbine and the hybrid energy storage system(HESS)containing the supercapacitor and the battery are modeled.The mathematical models of the modules of the doubly fed induction generator(DFIG)are detailedly analyzed,and the maximum power point tracking(MPPT)principle is realized;Besides,the decoupling control method of the rotor side converter and the grid side converter are studied.Moreover the mathematical model of battery and supercapacitor is modeled,and the strategy of constant power charge and discharge is used to control the energy storage system.Secondly,the frequency regulation method of DFIG wind turbine and energy storage system is studied.The influence of wind power permeability on the frequency regulation of power system is analyzed.By using virtual inertial control and pitch angle control method,DFIG wind turbine is involved in frequency regulation.The effectiveness of virtual inertial control in frequency modulation is verified by simulation,and the influence of control parameters of virtual inertial control is analyzed.The P-f droop control of energy storage system to participate in the system frequency regulation is proposed,and the effectiveness of the energy storage system to participate in frequency regulation is demonstrated by simulation.At last,the frequency regulation control strategy of DFIG wind-storage system under full wind speed is proposed according the frequency modulation characteristics of DFIG wind turbine and energy storage system.Firstly,the active power output of DFIG wind turbine participating in the system frequency regulation under differentwind speeds is analyzed,and a combined frequency control method based on virtual inertial control and pitch angle control is designed under high wind speed.The strategy of energy storage system participating in system frequency regulation is that supercapacitor is first used to regulate frequency.Then different wind-storage frequency regulation methods are adopted according to the difference of wind speed and the frequency deviation.Last,simulation results show that the proposed full wind speed frequency regulation strategy is effective.