Research On Wind Farm Frequency Modulation Based On Virtual Inertia Control

New energy generation is usually connected to the power grid through power electronic converters.When the system is disturbed,the inverters can not provide the necessary inertia and damping for the system quickly,which is not conducive to the stable operation of the power grid.As a kind of clean energy with abundant reserves,wind energy has many advantages.In recent years,more and more countries use it to generate electricity.Wind energy is time-varying and non-linear.In order to make efficient use of wind energy,the output of wind turbine only follows the change of wind speed,and can not provide inertia and frequency support to the system.To solve the above problems,a control strategy of virtual synchronous generator(VSG)is proposed in this paper.By means of control,power electronic inverters can simulate traditional synchronous generators in external characteristics,play a role in maintaining the frequency and voltage stability of the system,and improve the friendliness of new energy grid-connected generation.Firstly,this paper introduces the conventional constant voltage control strategy of the inverter unit,aiming at its weakness that the inertia is small and the frequency can not be adjusted,the idea of virtual synchronous generator is introduced.According to the traditional synchronous generator,the virtual synchronous generator mathematical model is designed.In the off-grid mode,the traditional constant voltage control and VSG control inverters are established to supply power to the load separately.By comparing the power,frequency and moment of inertia,the ability of VSG model to provide virtual inertia for the system is verified.Then the VSG-controlled inverters are connected to the grid to verify their grid-connected regulation performance.Then the VSG strategy is applied to the doubly fed wind power generation system,and a model of wind farm combined with VSG controlled energy storage unit is established in Matlab/Simulink,which is equivalent to a new virtual synchronous generator and merged into the grid.The simulation results show that the control strategy of virtual synchronous generator can effectively increase the inertia of the system,assist the wind turbine to participate in the primary frequency regulation of the system and improve the stability of the wind power Grid-connected by comparing with the wind farm grid-connected system without energy storage and the wind farm grid-connected system with traditional constant voltage control.Finally,aiming at the shortcomings of traditional PID control,a fuzzy-PID controller is designed and applied to the control algorithm of virtual synchronous generator,which further improves the dynamic performance of virtual synchronous generator.The conclusion that the response speed of virtual synchronous generator based on fuzzy-PID control is faster and the overshoot is smaller in the regulation process is drawn,which has certain reference value for practical engineering application.