Research On Grid-connected Frequency Stability Of Doubly Fed Wind Turbines Considering Wake Effect

As a new type of energy,wind power has continued to develop in recent years,and large-capacity wind power grid connection has become an inevitable trend.The vigorous development of wind power generation technology is a response to the strategic goal of energy structure adjustment,and it also has an adverse effect on the frequency stability of the system.There are problems to be solved urgently when the double-fed wind turbine is connected to the grid.When the doubly-fed wind turbine is connected to the grid,the rotor is decoupled from the grid frequency,which prevents it from responding to the frequency fluctuations of the power system like a conventional synchronous generator,which reduces the system’s frequency modulation capability;the wind farm is affected by wake effects,and each doubly-fed wind turbine The working state of the wind turbine is different due to different wind speeds,which increases the difficulty of frequency control of the wind turbine.This paper discusses and analyzes the existing frequency regulation technology of wind turbines,and conducts research work on the grid-connected frequency stabilization technology of doubly-fed wind turbines.Firstly,the basic structure and operating characteristics of doubly-fed wind turbines are discussed and analyzed.The mathematical model of each part of doubly-fed wind turbines,the mathematical model of wind speed,and the mathematical model of wind farm considering wake effect are established,and the simulation is carried out in Matlab/simulink.On this basis,the frequency modulation capability of the power system under different wind power penetration rates is analyzed.In order to reduce the system frequency stability caused by large-capacity wind power grid connection,this paper improves the system frequency stability by using doubly-fed wind turbines to participate in frequency modulation.Considering the wake effect in the actual operation of the doubly-fed wind turbine in the wind farm,the wind turbines are divided into regions based on the similarities and differences of the wind speed of the wake,and the wind turbines in the same area are operated in the same state.The additional frequency controller is adopted to make the current doubly-fed wind generating set have frequency modulation capability.By improving the inertial controller,the self-inertia of the doubly-fed wind turbine is coupled with the system frequency,and by controlling the wind turbine to keep part of the active output during normal operation for power backup.The control modes are mainly divided into three types.The frequency controller can determine the operating mode of the doubly-fed wind turbine based on the wind speed in the wind farm area,and maximize the frequency modulation potential of the doubly-fed wind turbine.The frequency modulation effect of the wind farm considering the wake effect is verified in Matlab / simulink.The simulation results show that the wind farm has a certain frequency modulation ability and the frequency stability of the system is improved.