Design And Control Of Axial Field Flux-switching Fault-tolerant Machines

With the development of electric vehicle(EV),the reliability and security of the motor drive system has been demanded highly in the recent years.EV can still work reliably when the motor drive system encounters some failures.Therefore,the design of fault-tolerant motor and control system has become the focus research all over the world.Axial field flux-switching fault-tolerant(AFFSFT)machine is a novel axial field permanent magnet machine.It combines the advantages of axial field permanent magnet machine and fault-tolerant machine,such as short axial size,small volumes,large power and torque density,and high fault tolerant capability,which make it suitable to the application field of direct drive electrical vehicles.In this dissertation,these key issues for AFFASFT machine are deeply and systematically studied,including the design theory,the method of analysis and optimization,the different topologies,the electromagnetic performance,and the control method.Both the simulant and experimental results are given to verify the theoretical analysis.This work lays an important foundation of the theory and technology in order to further improve the reliability of drive system,and increase alternative schemes of drive system for EV.The research works of this dissertation are as follows:1.The structure,the working principle and the windings' complementarity of a three-phase AFFSFT machine are analyzed in details.The power equation of AFFSFT machine and permeance between stator tooth and rotor pole are deduced,which lay theoretical base for the design of AFFSFT machine.2.The influence of structural parameters on inductances are investigated,including stator/rotor pole numbers,split ratio(Dsi/Dso),stator side tooth width,stator middle tooth width,thickness of permanent magnet,rotor pole width,air-gap axial length,and rotor axial length.Based on these,the design parameters of AFFSFT machine are optimized in order to attain the fault-tolerant design object of large self-inductance and small mutual-inductance,and the design scheme of AFFSFT machine is established.Taking advantage of three-dimensional finite element method,the static characteristics of AFFSFT machine are studied,and the FE-predicted results validate the correctness of the design theory and optimal method.3.The AFFSFT machines with different stator core shapes are proposed.Under the condition of the same outer dimensions,the performances of AFFSFT machines with different stator cores are studied and compared,including U-,C-,and E-shaped structures.The influences of rotor pole numbers,stator tooth/slot shape,and rotor pole shape on the machines are analyzed,and the three machines are optimized according to the back-EMF and cogging torque.The electromagnetic performances such as the flux density,back-EMF,cogging torque,inductance,and loss of the three machines are compared and analyzed,which validate E-core AFFSFT machines has better performances in contrast to the other machines.4.The math model of three-phase AFFSFT machine is established,and the system simulation models are done by MATLAB.The control method in normal and fault operation are proposed,respectively.The motor drive system are simulated and analyzed before and after the fault happens.The feasibility and effectiveness of control method is validated by the simulation results.5.Based on the structure of AFFSFT machine,a hybrid excitation AFFSFT machine is proposed.In this dissertation,the topologies of two different AFFSFT machines are compared,and the principle of regulating magnetic field by the DC field current is analyzed.Based on the design specifications of 6/14 pole AFFSFT machine,the electromagnetic performances of the two fault-tolerant machines are compared and analyzed,including the flux density distribution,back-EMF,inductance,torque,and fault characteristic.The fault-tolerant control for the hybrid excitation AFFSFT machine can be carried out by regulating the DC field current.6.The hardware circuit based on dSPACE is designed and developed,including the power converter,the drive circuit,the current detection circuit,and the conditioning circuit.The control software is also done,including the control and fault detection modules,and then the experimental platform is built,on the basis of which the performances of the AFFSFT machine are tested in normal and fault operation.The experimental results validate the design scheme of the motor and control system is effective and feasible.