Modeling And Control System Design Of Bearingless Permanent Magnet Synchronous Motors For Flywheel Batteries

Bearingless permanent magnet synchronous motor(BPMSM)is very suitable for the flywheel battery system due to its small size,high efficiency and high reliability.Compared with conventional motor and mechanical bearing system,the flywheel battery using BPMSM is smaller,more efficient and can reach the higher speed.Supported by the National Natural Science Foundation of China(51305170)and Six Categories Talent Peak of Jiangsu Province(2015-XNYQC-003),the studies on the suspension force modeling,performance analysis,nonlinear modeling of flux linkage and design of digital control system of BPMSM are carried out.Specific research contents are as follows:Firstly,the principle of BPMSM is introduced,and the mathematical model of suspension force of BPMSM is deduced by using Maxwell stress tensor method.Then,a surface mounted BPMSM(SBPMSM)and an interior BPMSM(IBPMSM)finite element model are built to verify the accuracy of the suspension force model.The SBPMSM and IBPMSM have the same stator,winding,and permanent-magnet air-gap flux density amplitude values.The simulation results show that the error between suspension force produced by IBPMSM and mathematical model are small,and IBPMSM can produce a larger suspension force than SBPMSM in the same suspension current.Finally,the flux linkage,inductance and torque are compared between SBPMSM and IBPMSM.The results show that the SBPMSM has small flux linkage harmonic and cogging torque.Secondly,due to the strong coupling and nonlinear relationship between flux linkage,rotor angle,torque winding current and suspension winding current,it is difficult to build precision flux linkage model based on the Least Squares Support Vector Machine(LSSVM).The adaptive weighted least squares support vector machine AWLSSVM is proposed to establish the nonlinear model between the flux and rotor angle,torque winding current and suspension winding current.By using this algorithm,the influence of gross error can be eliminated(or weaken),and the accuracy of flux linkage model can be improved.Then the Matlab is used to verify the accuracy of flux linkage model,and the results show that the flux linkage model established by AWLSSVM has high accuracy.Thirdly,torque winding and suspension winding systems are controlled by using space vector pulse width modulation(SVPWM)algorithm to realize the double closed loop and high precision control.High performance digital control system of BPMSM is developed based on TMS320F2812.For the hardware of the digital control system,the power circuit,current feedback system,photoelectric coding interface circuit,displacement interface circuit and dead zone protection circuit are investigated and designed.As for the software system,the main program design process,rotor initial position determination,rotor position and speed calculation are proposed.Finally,the experiment of BPMSM system is carried out based on the digital control system platform.The main contents of the experiment include the installation and debugging of the four displacement sensors,the SVPWM principle verification,the verification of static and dynamic suspension characteristics of the BPMSM.The experimental results show that the BPMSM can be work stably and generate suspension force in two cases.The experiment verifies the feasibility of BPMSM system,which provides a reference value for the future research.