Research On Design Of A New Dual Stator Doubly-fed Hybrid Excitation Machine Applied In Electric Vehicles Of Master Thesis

With the energy crisis and environment pollution increasing,energy saving and environmental protection have been on the agenda and paid much attention.Traditional internal combustion vehicles emissions and consumption of fossil fuels are contributing to environment and energy problems.Due to the advantages of low pollution and high efficiency,electric vehicles(EVs)are supported strongly by governments and bring unprecedented opportunities to car industries.In the near future,if EVs intend to replace internal combustion vehicles completely,the driving performances are comparable to that of internal combustion vehicles and even more excellent.Thus,complex operation conditions of EVs set higher requirements for the motor drive system.Tradition permanent magnet synchronous machine(PMSM)possesses high power density,high torque density,high efficiency and other advantages,which become the main research scheme of drive machine in electric vehicles.However,there are two major problems in traditional PMSM: difficult airgap field regulation and demagnetization of permanent magnets,which limit its promotion and application.Therefore,developing the high output capability,high reliability and wide speed range new motor drive system is particularly important and meaningful.Compared with Stator-PM machine,Rotor-PM machine is more mature in application of EVs.How to achieve high output,high reliability and wide speed range in rotor-pm machine is the key problem to be solved and has broad market prospects.Breaking through the shackles of the traditional Rotor-PM brushless hybrid excitation machine and by incorporating dual-stator,consequent-pole and AC excitation theory,a new dual-stator doubly-fed hybrid excitation machine is proposed in this thesis.The characteristics of this new machine topology are as follows:(1)the armature winding and excitation winding are housed in the outer stator and inner stator respectively in order to reduce coupling between them and take advantage of inner space of machine;(2)NS consequent-pole is adopted in the rotor,namely,NS magnetized PM-pole and ferromagnetic-pole are arranged alternatively.This can save the amount of PMs and ferromagnetic-pole acts as the pole that fluxes can be regulated;(3)the excitation winding is in the inner stator which can avoid brushes and slips,and the design of AC excitation can regulate outer airgap field and can provide output torque in inner airgap;(4)the armature winding is composed of three-layer interval concentrated winding which incorporates NS consequent-pole and concentrated winding effectively,thus improving the deterioration of waveforms of induced voltage caused by unbalanced outer airgap flux of NS consequent-pole and achieving the high reliability and fault-tolerance of concentrated winding.The new dual-stator doubly-fed hybrid excitation machine is as a new machine topology which can be applied to EVs require high output,high reliability and wide speed range,its operation principle,design method and control strategy differs from that of traditional Rotor-PM hybrid excitation machine,so many fundamental problems remain to be researched.In this thesis,the state of less-rare-earth machine and Rotor-PM brushless hybrid excitation machine are introduced firstly.Then,electromagnetic performances of consequent-pole permanent magnet synchronous machine are analyzed.Based on the analysis,a new dual-stator doubly-fed hybrid excitation machine is proposed and its topology and operation principle are also introduced.Then,the design of the 2kW prototype is discussed in detail,including the number of phases,pole/slot combination,armature winding,excitation winding and so on.Besides,by adopting finite element analysis software Ansoft,a two-dimension simulation model of the proposed machine is established and the electromagnetic performances are analyzed.And the effect of the main structure specifications such as PM-pole and ferromagnetic-pole on performances of machine is investigated.Based on the forward studies,the machine is optimized.The mathematical model of the proposed machine is established and the simulation model is built on Matlab/Simulink to simulate speed characteristic of this machine.Finally,a 2kW prototype is tested including resistance and inductance,back-EMF and so on,which validate rationality and correctness of proposed new dual-stator doubly-fed hybrid excitation machine.