The Research On Smoothing The Fluctuation Of The Permanent Magnet Direct-drive Wind Power Turbine Based On Hybrid Energy Storage System

In recent years,with the rapid development of the global wind power industry,the proportion of grid connected wind power increased gradually.Because of the randomness and volatility of wind power generation,large-scale grid connected wind power will have a great impact on the power quality and stability of power grid,making use of energy storage technology can effectively solve these problems in wind power system.Therefore,this paper proposes the two-stage VRB-SC hybrid energy storage system to smooth the power fluctuation of directly-drive permanent magnet synchronous wind turbine.The work done in this paper is as follows:Firstly,the operating principle of directly-driven permanent magnet synchronous generation(PMSG)wind power generation and the mathematical model of wind turbine,permanent magnet synchronous generator and back to back converter are analyzed.On this basis,the control strategies of the machine side converter and the grid side converter are established.And in Matlab/Simulink environment,2MW directly-drive permanent magnet synchronous wind turbine simulation mode is built.Secondly,the operating principle and equivalent circuit model of vanadium flow battery(VRB)and super capacitor(SC)are analyzed,and in Matlab/Simulink environment,the vanadium flow battery and the super capacitor are simulated.Thirdly,in order to make better use of storage system to smooth the fluctuation of wind power generation,two-stage VRB energy storage system is used to expand capacity.This paper proposes the optimization power distribution control strategies of two-stage VRB storage and the double closed loop control strategy which is established to switch charge-discharge style as a constraint of the state of charge(SOC)of VRB.The optimization power distribution control strategies of two-stage VRB storage are proposed by taking the SOC value of each VRB as priority target selection and using the maximum charge and discharge power as the constraint conditions.And in Matlab/Simulink environment,using two-stage VRB energy storage system with different SOC values to smooth wind power fluctuation under the wind speed variation is simulated,and the simulation results are compared by using the average distribution strategy of active power,The simulation results show that the proposed control strategy can not only smooth wind power fluctuation,but also ensure the battery work in the safe operation region,and could reduce the discharging and charging times of VRB,which can prolong battery life.Finally,this paper proposes the two-stage VRB-SC hybrid energy storage system to smooth the power fluctuation of directly-drive permanent magnet synchronous wind turbine.The power required for the energy storage system is distributed through the low-pass filter,the two-stage VRB undertakes low-frequency part and the SC undertakes the high-frequency part.Two-stage VRB energy storage system adopts the optimizationpower distribution control strategies of two-stage VRB storage and the double closed loop control strategy which is established to switch charge-discharge style as a constraint of the state of charge(SOC)of VRB,and SC energy storage system adopts the double closed loop control strategy,the outer loop of power and the inner loop of current.And in Matlab/Simulink environment,using hybrid energy storage system to smooth wind power fluctuation under the wind speed variation is simulated.The simulation results show the correctness and validity of the proposed control strategy.