Research On Frequency Modulation Control And AGC Optimal Control Of Electrical Power System With Wind Power Generation

As the most potential renewable clean energy in the future,wind power plays a positive role in alleviating energy shortage,environmental pollution and optimizing power supply structure,so it attracts the world's wide attention and has been vigorously developed and utilized.Doubly-fed induction generator(DFIG)based on wind turbine has been the main type of wind generator in China,but it's decoupling control of rotor speed and power system frequency make it unable to respond to the change of power system frequency.In recent years,with large-scale wind farms gradually incorporated into the grid and the increasing permeability of wind power,the power grid frequency regulation pressure will be increasing.Therefore,how to reduce the impact of the system stability when the large-scale wind power on-line,and how to make the wind turbine output active power smoothly,and the method of connecting wind turbine to participate in the frequency adjustment,all above need to be addressed.In this paper,the mainstream DFIG is the research object,and on the basis of the existing research results,the following work was done:Firstly,aiming at the problem of frequency secondary drop caused by the speed recovery of a single DFIG,this paper presents a method of speed recovery based on Butterworth variable PI parameter control to slow down the active power absorption from the power grid.In the case of multiple DFIGs,the delayed speed recovery strategy based on Butterworth variable parameter PI and the optimal grouping strategy of wind farm are designed to alleviate the secondary frequency drop caused by wind farm withdrawing from frequency adjustment.Then,according to the advantages and disadvantages of DFIG virtual inertial control and pitch angle control,a control method combining DFIG virtual inertial and pitch angle control is presented.When the system is disturbed by load,the virtual inertial control provides active power support to the system in a short time,then DFIG need to enter the speed recovery link,and now the pitch angle control starts to operate,and it can provide active power for virtual inertia exit and continuously provide active power support for the system to reduce the frequency stability deviation.Aiming at the problem that DFIG and synchronous machine participate in the power distribution of frequency modulation in coordination,this paper analyzes the principle of power distribution of the primary and secondary frequency modulation system in the process of DFIG and synchronous machine through the proportion of the adjustment coefficient.The simulation results show that the coordinated control can alleviate the frequency modulation pressure of synchronous machine.Finally,aiming at the problem of wind power participating in the automatic generation control of interconnected power system,this paper presents the AGC optimal control based on PSO-GSA algorithm.The improved virtual inertial control has been introduced to make DFIG have better frequency response,at the same time,the parameters of PID controller and PI controller of DFIG's speed control unit are optimized by PSO-GSA algorithm in order to quickly eliminate the area control error and rotor speed error,improving the dynamic performance of the system.