Optimization Research And Design Of Brushless Doubly-fed Machine Based On Improved Multi-Objective Particle Swarm Algorithm

Brushless Doubly-fed Machine(BDFM)is a special AC motor of a new structure that developed in recent years.Because of its excellent performance in AC Drive System,especially the high power frequency control system,it has a wide range of application prospects.The BDFM is different from an ordinary AC machines,it originated from the two cascade wound-rotor asynchronous motor.It has two stator windings that are power windings and control windings.The magnetic field generated by the two stator windings is indirectly coupled with the rotor,and by adjusting the frequency of the control winding to reach goal of speed adjusting.Because of the above reasons,it has a huge energy saving potential in the load speed control system such as fans,pumps and so on.The performance of BDFM mainly depends on its rotor.There are some disadvantages of the reluctance rotor BDFM widely used at home and abroad so far,such as poor rotor coupling ability,low conversion efficiency of magnetic field,high harmonic content,high loss and low efficiency.To solve above-mentioned problems,in this essay the parameters of BDFM were optimized.According to the domestic and foreign references,this paper discusses the current research situation and development of BDFM.And the basic working principle and operation mode of the motor are analyzed in detail.Based on the above research,the mathematical model of BDFM in three-phase static coordinate system and d-q coordinate system was established,and its equivalent circuit was established based on mathematical model.Then the electromagnetic design features of BDFM are different from the general AC motor,so the electromagnetic design of BDFM is summarized in this paper.And on the basis of this summary,a reluctance rotor BDFM was designed that its power winding is 4 pairs poles and the control winding is 2 pairs poles.And next,according to the design principle of BDFM,the main parameters and magnetic circuit of the motor were calculated and the main body of BDFM was designed.The time-varying electromagnetic field and the magnetic vector potential equation of BDFM are derived by the Maxwell equations,and then the boundary conditions of the finite element analysis of the motor was established.Finally,the electromagnetic field,the magnetic flux density and the core loss of the reluctance type BDFM are calculated by using Ansoft software.It was concluded that the optimization design of the motor structure was the fundamental way to improve the effect of the magnetic field.At last,on the basis of the study of the improved multi-objective PSO algorithm,the improved multi-objective PSO algorithm was introduced to the optimization design of BDFM.In this paper,the optimization design mathematical model of BDFM was established,and the suitable optimization design variables and objective function are selected,and the design variables are restricted to the feasible range of variation.Finally,the optimization results of the motor parameters,the efficiency,the average torque and the torque ripple are obtained by the improved multi-objective PSO algorithm.