Research On Primary Frequency Regulation Of Wind Farm Based On Energy Storage

With the development of wind power and the increase of capacity and scale of wind farm,wind power generation,due to the uncertainty of output power and the decoupling of doubly-fed generator and system frequency,does not possess the inertia of traditional units.After its grid-connected operation,it will bring different impacts on system peak-shaving and frequency-shaving,increasing the load of system peak-shaving and frequency-shaving units,and energy storage system with it.Rapid response ability and high energy conversion efficiency can help to absorb new energy and improve the effect of peak shaving and frequency regulation.Therefore,it is of great significance to study and improve the frequency regulation capability of wind power system itself and the primary frequency regulation strategy of wind energy storage and wind power participation system.Firstly,the structure of doubly-fed generator and the mathematical models of each module are analyzed,and the control mode of converter on machine side and network side is also analyzed.The frequency response of power system and the frequency characteristics of power system with wind power under different permeability are analyzed.Subsequently,the characteristics of different types of energy storage are compared.Super capacitor and battery-based energy storage systems are selected.The models of super capacitor and battery internal resistance are established respectively.The models of battery and super capacitor are built by matlab,and their charging and discharging characteristics are obtained.On this basis,a power switching circuit based on DC-DC converter is designed,and a suitable hybrid energy storage topology is selected to realize bidirectional and fast energy exchange between the outside and the energy storage system.Then the frequency regulation method of doubly-fed generator and energy storage module is studied.The virtual inertia control and load-shedding mode are designed to make the fan participate in the system frequency regulation.The virtual inertia control can get the reference value of the rotor side current through the additional frequency control link,release the rotor energy.The load-shedding mode can reserve the pitch angle,release the pre-power through the response frequency deviation,and verify the two by simulation.For energy storage participating in frequency regulation mode,the frequency flow of single energy storage support system under droop control mode is designed,and the control effect is verified.Finally,aiming at the problem that frequency oscillation and traditional sag control may lead to battery overcharge and overdischarge caused by single energy storage frequency regulation mode,an adaptive hybrid energy storage control mode is designed,which improves the traditional sag mode,and combines the advantages of two single energy storage frequencyregulation modes.The simulation results show that the control method can not only avoid the overcharge and overdischarge of energy storage system,prolong the life of energy storage system,but also effectively reduce the vibration amplitude and time of system frequency.