Study Of Dynamic Magnetic Equivalent Circuit Model And Design Optimization Of Brushless Doubly-Fed Machine

Brushless Doubly-Fed Machine(BDFM)eliminates brush and slip ring,improves the reliability of system.Less inverter capacity and adjustable power factor make it has good potential applications in the fields of variable-frequency adjustable-speed motors and variable-speed-constant-frequency generators.However,the efficiency of BDFM with cage rotor is not as high as desirable and few effective tools can be used to quickly and correctly analyze its operation performances due to its special winding structure and complex electromagnetic coupling mechanism.The methods of combining theoretical analysis,Finite Element Analysis(FEA)and experimental research are used to study the modeling and solving method of Dynamic Magnetic Equivalent Circuit(DMEC)model and design optimization method of BDFM with cage rotor.Firstly,the basic structures and operation theories of BDFM are briefly introduced.The DMEC model of a prototype BDFM with cage rotor was analyzed and built up by considering the influences of its special structure,iron saturation and rotor rotation.The topology and reluctances of the DMEC model were studied and analyzed.Secondly,referencing the method of analyzing electric circuits,three methods,including node method,mesh method and transmission line modelling method,were used respectively to build up the algebraic equations of the DMEC model of BDFM with cage rotor.By coupling the algebraic equations and the differential equations,the DMEC model was solved,and then the advantages and disadvantages of the three different methods were compared.Thirdly,the DMEC model was used to analyze the performances of BDFM with cage rotor at different operating conditions.The correctness of the DMEC model was verified by comparing its results with the FEA and test data.Fourthly,aiming to improve the efficiency of BDFM with cage rotor,the structure parameters of the prototype were analyzed by Taguchi method and 9 important design parameters were selected as optimal variables.Finally,the differential evolution algorithm(DEA)was improved and used to solve the design optimization problem of BDFM with cage rotor to get the optimal results.The optimal results were validated by FEA.The results show that the proposed DMEC model and improved DEA can be used to enhance the efficiency of BDFM with cage rotor.The prototype efficiency is significant improved after optimization.The research results of this thesis enrich the methods to analyze the operation performances of BDFM with cage rotor,provide the theoretical and the technical supports for improving electromagnetic design and efficiency of BDFM with cage rotor.