Low Frequency Load Reduction Optimization Strategy For Power System Considering Wind Power And Flexible Load

Low-frequency load reduction is the last line of defense to maintain the safe and stable operation of the power system.When serious active power shortage occurs in the system,the low-frequency load reduction device can recover the system frequency by removing certain non-important loads,and the active power tends to balance again.With the rapid development of wind power primary frequency modulation and virtual inertia control technology as well as the increasing number of flexible adjustable loads,it has a very important research significance for stabilizing the frequency stability defense line of power system and improving the safety and reliability of system operation.Therefore,it is necessary to optimize and adjust the low-frequency load reduction scheme considering wind power and flexible adjustable loads.On the basis of avoiding the phenomenon of load overcutting,the economy of low frequency load reduction process is guaranteed.The research contents and ideas of this thesis are as follows:Aiming at the model of wind power and flexible load participating in low frequency load reduction,the frequency response model of doubly-fed induction wind turbine is elaborated,and the wind speed and fan model,the two-mass based transmission shafting model,pitch Angle control model and power support model are analyzed in detail.Secondly,the air conditioning load in the flexible adjustable load is studied.The frequency response model,response process and principle of fixed-frequency air conditioning and variable frequency air conditioning involved in the system are analyzed,which lays a good foundation for the study of frequency characteristics and low-frequency load reduction of power system considering wind power and flexible load in the following thesis.Aiming at the study on the influence of wind power and flexible load participating in frequency modulation on the system frequency change and the removal amount of low-frequency load,the frequency characteristics of power system,wind power and flexible load are modeled and analyzed,and the influence of the access of wind power and flexible load on the dynamic frequency change process of power grid and the steady-state value of frequency under low-frequency events is analyzed in the actual regional power grid in Northeast China.In addition,the influence of wind power and flexible load participating system frequency response on low frequency load reduction process under different operating conditions is analyzed.Based on the above content,the optimization entry point of low frequency load reduction scheme is analyzed.Aiming at the low frequency load reduction and anti-overcutting optimization setting of power grids containing wind power and flexible load,a parameter setting method of load reduction scheme based on power deficit offset was proposed considering wind power and flexible load participating in the system frequency response.Improved grey Wolf optimization algorithm was used to solve the optimization model.The load reduction scheme parameters were adjusted through load reduction reduction values of different weights assigned to each basic level load reduction ratio parameter.The indicators such as low frequency load reduction and load reduction and frequency recovery value were solved through the example of northeast regional power grid.The load overcutting situation of load reduction optimization scheme was analyzed,and the effectiveness and superiority of the low frequency load reduction and anti-overcutting setting method based on the power gap principle was verified.Aiming at the low frequency load reduction optimization strategy considering the flexible load regulation cost and load excision cost,in order to minimize the total cost on the load side of low frequency load reduction,a multi-objective optimization model was constructed with the minimization of the flexible load regulation cost and the minimization of the load excision cost respectively,and the multi-objective grey Wolf optimization algorithm was used to solve the model.Through the example of northeast regional power grid,the flexible load regulation cost and load removal cost were solved,the total cost of load side under the optimization scheme was analyzed and compared with the original scheme,and the low frequency load reduction optimization strategy considering the flexible load regulation cost and load removal cost was verified to improve the overall economy of the system.