Study On Control Strategy Of DFIG Participating In Frequency Regulation And Operation Control In Power Systems

With the depletion of traditional energy sources,the environmental problems caused by the use of traditional energy sources have become increasingly serious,and people's awareness of environmental protection and energy crisis has continued to increase.The development and utilization of new energy has become an important way to solve the energy shortage and environmental pollution problems that are facing today.Thanks to the rapid development of aerodynamics and power electronics,wind power technology has developed rapidly.The wind turbine has been pitched from the very beginning to the pitch.Double-fed wind turbine(DFIG),as a typical variable-pitch wind turbine,can not only improve the wind energy utilization rate,but also can achieve variable-speed constant-frequency operation.Therefore,doubly-fed wind turbines are becoming more and more popular among people and have become the primary choice for the construction of wind farms.However,due to its own control system,the DFIG completely decouples the rotor speed of its generator from the frequency of the grid and cannot respond to changes in the system frequency.When more and more non-frequency-modulated doubly-fed wind turbines are integrated into the power grid,the frequency-regulation pressure of conventional turbines will increase.Therefore,it is great significance to study how to implement the frequency regulation capability of the DFIG and the cooperative tuning strategy of the grid-connected and conventional generators.In order to DFIG has enough active power reserve to adjust the output when participating in grid frequency tuning,fans will usually perform load shedding to save some of the active power.In this paper,according to different wind speed regions,frequency control links are introduced on the basis of load shedding operation control,and different frequency tuning capabilities of DFIG are realized.Simulation analysis was carried out by MATLAB/Simulink simulation product to verify the effectiveness and feasibility of the control method.With the gradual expansion of wind farm scale,in order to simplify the model and shorten the calculation time,this paper proposes an equivalent method based on the fan operation mode to divide the fleet,and comprehensively considers the wake effect and time-delay effect existing in the wind farm..Equivalent modeling through the method proposed in this paper can not only obtain a more accurate equivalent model,but also can quickly calculate the active reserve in the wind farm,which can provide a certain basis for wind power participation in frequency modulation of the grid.When more and more frequency-adjusted DFIGs are connected to the power grid,they are bound to cooperate with traditional synchronous machines.Therefore,according to different wind speed regions and system frequency deviations,this paper proposes a cooperative frequency modulation strategy for DFIG and traditional synchronous generators.The related parameters in the synchronous generator and frequency modulation controller were set.Finally,it was verified in the MATLAB/Simulink simulation product.Through the simulation results,through the adjustment of the tuning coefficient,DFIG was able to use the reserve active reserve for the adjustment of the system frequency as much as possible within the allowable range of frequency deviation.Not only reduces the pressure of the synchronous machine's frequency modulation,but also reduces the "discarding wind" brought about by the deloading operation and improves the economy.