Research On Modeling And Control Of Aircraft Variable Speed Variable Frequency AC Generator

At present,the proportion of aircraft electric power system（EPS）in the aircraft energy system is increasing.EPS is developing from more electric to all-electric,and the demand for power generation system is also increasing.From the initial low voltage DC EPS to variable speed variable frequency EPS,variable speed variable frequency AC generator has become the mainstream of aircraft power system generators.Because of the increase of power system power,people also put forward higher requirements for the dynamic and steady-state performance of power generation control system.There are many problems in the research of power generation control system directly on the physical object,such as long development time of controller and easy damage to the physical object.The establishment of accurate and fast system simulation model and the research of control system based on the simulation model can accelerate the development of controller and improve the economy.Therefore,this thesis conducts the research on modeling and control of aircraft variable speed variable frequency AC generator system,and the research work is as follows.The mathematical models of permanent magnet synchronous generator,excitation synchronous generator,rectifier and excitation power circuit in variable speed variable frequency AC generator are analyzed,and the circuit characteristics under two working modes of excitation power circuit module are deduced in detail.The transfer function model of power generation system is established,and the transfer function model is verified by circuit simulation model.The transfer function of power generation system under different working conditions is obtained by system identification.The effects of engine speed disturbance,load disturbance and harmonic of measurement signal in power generation system are analyzed.Three system simulation models are established:circuit simulation model,improved transfer function simulation model and discrete simulation model.In view of the long running time of the circuit simulation model and the problem that the traditional transfer function simulation model cannot directly reflect the system response when the parameters of the controlled object change,the transfer function simulation model is improved.The output of the controller is provided to the controlled object under different working conditions at the same time,and then the output of the corresponding controlled object is selected as the feedback to simulate the response of the control system when the parameters of the controlled object change.When the simulation step length is 10^-7s and the simulation time length is 0.1s,the running time of the model is reduced from 100s to 4.7s.Aiming at the problem that the circuit simulation model and the improved transfer function simulation model are inconvenient to use the optimization algorithm to optimize the controller parameters,the improved transfer function simulation model is discretized to obtain the discrete simulation model.The running time of the model is reduced to 0.04s,and the optimization algorithm is convenient to use.A kind of Fuzzy PID controller,namely Matrix Fuzzy PID controller,is proposed.In view of the problem that the parameters in the design of the traditional Fuzzy PID controller are coupled with each other,and it is difficult to obtain the parameters by using the optimization algorithm,the Matrix Fuzzy PID controller uses the second-order tracking differentiator to replace the classical differentiator.The establishment of coefficient matrix replaces the establishment of rule base,fuzzy reasoning and defuzzification in fuzzy control;the two-dimensional coefficient matrix is reduced to one-dimensional vector,and the numerical solution of the matrix is equivalent to the solution of one-dimensional vector.Aiming at the optimization problem of coefficient matrix parameters of Matrix Fuzzy PID controller,a global optimization algorithm-state transition algorithm is improved to solve the optimization problem.The improved state transition algorithm is State-Driven State Transition Algorithm（SDSTA）.Based on the difference between before and after the state solution replacement,SDSTA changes the size of the state set in real time,and verifies the performance of SDSTA by comparing three test functions.An error evaluation method for the performance of the control system in this thesis is designed,that is,the weighted integral absolute error,weighting the errors of different sizes to different degrees,and using the new error evaluation method as the loss function of SDSTA.The effectiveness of the optimized Matrix Fuzzy PID controller for the power generation control system is verified on the circuit simulation model,and the dynamic and steady-state performance of the power generation control system is improved.