| A flywheel battery is a new physical energy storage pattern,and it has advantages of high power density,high safety performance and non-polluting.It can improve the power performance and economy of electric vehicles when it is applied to electric vehicles.Bearingless permanent magnet synchronous motors(BPMSMs)which appeared in recent years are a new type motors with function of suspension and rotation.When it is applied to flywheel battery system,the rotate speed of flywheel can be improved furtherly,and the structure of system can be simplified.Under the supports of National Natural Science Foundation of China(51305170),Outstanding Youth Foundation of Jiangsu Province(BK20170071),and Key Project of Natural Science Foundation of Jiangsu Higher Education Institutions(17KJA460005),some studies are carried out,including math model of suspension force,electromagnetic characteristics,thermal field modeling,digital control system and experiments.The detailed contents are as follows:1.The Maxwell force in BPMSM is explained,and the principle of suspension force generation is introduced.According to the Maxwell stress tensor method,the equation of the magnetomotive force in air gap is deduced,and then the mathematical model of the suspension fore is deduced.2.Three kinds of BPMSMs with different rotor structures are built by using the method of finite element parameterized modeling,and then the torque performance and suspension performance are compared.Given that the BPMSM is used for flywheel battery,the interior BPMSM(IBPMSM)is selected as the main research object after comprehensive consideration.Then,the other electromagnetic characteristics,including magnetic field,inductance and induced electromotive force,are investigated in detail.3.There are two sets of stator winding in BPMSMs,resulting in more losses.Therefore,the study about thermal field modeling is needed to resolve this problem.The core loss and permanent magnet(PM)loss are calculated by finite element method,and then two losses are transformed into heart source.Then,the air gap and winding insulation are equivalently treated,and the steady thermal finite element model of the BPMSM is built in ANSYS/Workbench.In addition,the corresponding heart source,thermal conductivity coefficient and convective heat transfer coefficient are applied in ANSYS/Workbench,and then the thermal field of the BPMSM in three kinds of operation conditions are calculated and analyzed.4.Due to the disadvantage of the traditional control strategy,a control strategy based on space vector pulse width modulation(SVPWM)algorithm is proposed,which can realize high-efficient control for torque and suspension force of the BPMSM.Based on the core chip TMS320F2812,the hardware and software systems are built,which lay a basic for further experimental study of the BPMSM.The hardware systems,including power supply circuit,interface circuit of current signal,interface circuit of radial displacement signal,interface circuit of photoelectric encoder signal,PWM protection circuit and driving circuit,are designed.Furthermore,the software systems,including calculating module of rotor speed and position,initial positioning module of rotor and so on,are compiled.5.The experiment platform of BPMSM is constructed based on the design of hardware and software systems,and then some reliable experiments,including steady suspension experiment and suspension operation experiment,are carried out.The experiment results show that BPMSM can operate stably under both experimental conditions. |
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