Research On Frequency Regulation Strategy Of Doubly-fed Induction Wind Generator With High Wind Power Penetration

The demand for rapid economic development and the desire for a better living environment make renewable energy have broad prospects for development,in which wind energy has developed rapidly in recent years with its cost and technology advantages.Doubly-fed induction generator is the most mainstream model in the world wind power market,but the operation mode of its power decoupling control makes its rotor speed decoupled from the power grid frequency,which makes the DFIG unable to respond to the change of system frequency.With the large-scale integration of DFIG into the power grid,the frequency stability of the system decreases and the pressure of frequency regulation increases.Therefore,it is of great significance to study the control strategy of DFIG participating in system frequency adjustment for the further development of wind power industry.In this paper,doubly-fed induction generator is taken as the research object to study the frequency regulation strategy based on the existing methods.Firstly,this paper establishes the mathematical model of DFIG,studies the power decoupling control strategy and analyzes the response process of DFIG when the system load changes.Then it is pointed out that the large-scale interconnection of DFIG will reduce the equivalent inertia of the system and change the frequency response characteristics because of its external performance of “zero” inertia.In view of this situation,the frequency response characteristics of traditional power system and high wind power permeability system are analyzed and compared,and it is pointed out that the higher the wind power permeability,the worse the frequency stability of the system.In order to enable DFIG to respond to the frequency change,the theoretical analysis and simulation verification of the control method of DFIG participating in the system frequency regulation are carried out.In order to further improve the frequency regulation capability of DFIG,this paper focuses on the selection of control coefficients in DFIG comprehensive inertial control strategy,analyzes the influence of inertial control coefficient and droop control coefficient on DFIG frequency regulation performance,and optimizes the control coefficient to meet the frequency regulation demand under different wind speed.In addition,because the traditional inertial control strategy can not balance the two control objectives of reducing frequency deviation and avoiding frequency oscillation,an inertial control strategy with additional variable coefficient fuzzy control is proposed.The proposed strategy only retains the droop control loo,takes the frequency deviation and the frequency deviation change rate as the input of the fuzzy controller,and the Droop control coefficient as the output of the fuzzy controller,so as to optimize the utilization the rotational kinetic energy of DFIG and improve the frequency regulation ability.The simulation model of the relevant control strategy is built in MATLAB/Simulink platform,and the influence of DFIG on system frequency under traditional power control,traditional inertial control and improved inertial control is analyzed,compared and verified.Finally,an experiment platform with DSP28335 as the control unit is set up,and the hardware circuit and software program of the experimental platform were introduced in detail.Some relevant theories are verified by the experimental platform,and the experimental results prove the correctness and feasibility of the theory.