Control Strategy Of Dfig Participating In Secondary Frequency Control And Corresponding Coordinated Operation Of AGC

With the depletion of fossil energy and the gradual seriousness of climate change caused by greenhouse gases,renewable energy represented by wind power has become a trend of energy development due to its environmental protection and sustainability.However,the randomness and volatility of the output of the wind turbine cause the disturbance of the power supply to increase,which brings a series of challenges and problems to the automatic generation control(AGC)in the power system.In the past,wind farms were only treated as “negative” loads,and AGC stabilized load disturbances by systematically adjusting power output.With the increasing penetration of wind power,it is difficult to effectively suppress the power fluctuation of large-scale wind power by relying on the rotating standby of traditional power supply.Therefore,it is of great practical significance to explore the new method of wind farm participation in AGC control.Firstly,in view of the existing hysteresis effect of the wind power curtailment control(WPCC),this paper proposed an improved control strategy,namely wind power curtailment control considering secondary frequency control using self-reset integrator(WPCC-CSFC-USI).In order to achieve the required limit power level,the solution preferentially controls the wind turbine speed by adjusting the electromagnetic torque,and adjusts the pitch angle to limit the power output when necessary,which optimizes the operating condition of the pitch angle servo mechanism.By introducing the AGC control signal,the wind turbine converts the above-mentioned rotating standby into active support,thereby realizing its active response to the AGC under emergency conditions.The simulation results show that the proposed strategy effectively eliminates the adverse effects of the above-mentioned hysteresis effect,and realizes an organic combination between WPCC and secondary frequency control.Secondly,taking the improved 4-machine 2-area system as an example,this paper adopted the fixed frequency and tie-line power control(FBC)as the load frequency control coordination strategy of the two-area power grid,and further built the AGC three-layer control model that takes into account wind power generation.Finally,based on the above research,this paper designed an AGC coordination strategy that takes into account wind power generation.Under the premise of considering the active reserve capacity of the wind farm,the strategy calculates the area control error(ACE)and selects the behavior of the generator set by referring to the four control areas of the ACE,and coordinates the output of wind turbines and synchronous generators by setting different participation factors.Consequently,the priority is given to the wind power generation to participate in the secondary frequency control of the grid under certain conditions.The simulation results show that the proposed strategy effectively reduces the active power of synchronous generators,and continuously shares the secondary frequency control pressure of synchronous generators,which improves the utilization rate of wind power.