Research On The Grid Connected Characteristics Of Wind Farm Based On Virtual Synchronous Generator

Coping with climate change has been a common problem in the 21st century,and the application of new energy is an important measure to alleviate the contradiction with nature.Wind energy is easy to obtain and China's total wind energy reserves are huge,ranking the third in the world,and wind power generation is pollution-free,with small investment and broad prospects for development.But the wind in nature is changing at any time,so the wind power generation has uncertainty and volatility.The grid connection of wind turbine is controlled by frequency converter,which is usually decoupled from the system frequency,so it is not like the traditional synchronous generator that can respond to the system frequency change by changing the generator speed.From the point of view of system,wind farm is like a generator without inertia,and its moment of inertia is zero.With the increasing permeability of wind power,the frequency modulation ability of the system will be weakened.As a control method which can make the new energy generation system have certain inertia and damping coefficient,virtual synchronous generator emerges as the times require.It plays a supporting and mitigating role in the power system with new energy generation equipment connected to the grid.The main contents of this paper are as follows:(1)This paper studies the working principle,mathematical model and equivalent circuit of wind turbine power generation,as well as the regulation and control of wind turbine.In this paper,the fixed pitch control is used,that is,only changing the wind speed to control the power generated by the wind turbine,in which the combined wind model is added to more closely simulate the change of wind speed in nature.(2)The working principle,mathematical model and equivalent circuit of the virtual synchronous generator are studied.Based on the simplest second-order model of the synchronous generator,an adaptive model is added to the control strategy to make the frequency change of the system more moderate.(3)Firstly,the system model of single wind turbine connected to the grid is built.With the help of virtual synchronous generator and energy storage,the wind turbine can input electric energy with smooth waveform to the system.Then,the small-scale power system model of three steps and nine nodes composed of traditional steam turbine is built.On this basis,when the wind turbine is incorporated into the system,the virtual synchronous generator regulates the system frequency and works The role of rate moderation.The results show that with the participation of virtual synchronous generator,the power fluctuation of the system is well suppressed,and the control strategy is verified in Matlab / Simulink platform.