Research On Torque Control Methods Of High Power Density Permanent Magnet Synchronous Motor

With the development of industry and new energy vehicles,Internal Permanent Magnet Synchronous Motor is one of the most widely used motors in industry and transportation which is required to have the characteristics of simple structure,high power density,wide speed range and so on.The high power density IPMSM has a high electromagnetic load,which is easy to saturate the magnetic circuit,resulting in nonlinear change of motor parameters.Meanwhile,the d-q axis is not completely decoupled,resulting in cross-coupling inductance.Both the traditional model and the traditional control method are based on constant parameters and complete decoupling of d-q axis,so the traditional control method is no longer suitable for high power density IPMSM.In order to solve above problems,this paper takes high power density IPMSM as the research target,the nonlinear model,Maxwell motor simulation considering cross coupling and saturation of magnetic circuit,nonlinear parameter change and control strategy are analyzed,in order to make high power density IPMSM have better torque control performance,less loss,wide speed range and high torque output capacity.This paper has researched the above issues :(1)The traditional linear model is no longer suitable for high power density IPMSM because of the nonlinear change of motor parameters and the strong coupling of motor.Based on the analysis and derivation of linear models of permanent magnet drive motors in different coordinate systems,this paper analyzes the inductance calculation model of high power density IPMSM,and Then,a nonlinear IPMSM model considering cross saturation effect is built.On this basis,the torque and loss of highpower density motor are analyzed and deduced,and the corresponding conclusion and loss calculation formula are obtained.(2)In order to analyze the influence of magnetic cross saturation on the nonlinear variation of IPMSM parameters,a finite element simulation model of high power density IPMSM was established.The relationship between flux and current is solved by simulation model,and the nonlinear variation of inductance is calculated by frozen permeability,then the nonlinear variation of IPMSM torque caused by cross coupling and magnetic circuit saturation is calculated.(3)In order to account for the influence of cross coupling and magnetic saturation on the control performance of IPMSM,an improved control algorithm of motor torque considering the influence of nonlinear inductance is proposed in this paper.According to the optimal stator current and given torque,the difference between the target value of voltage and torque and the actual value is calculated,and then the current increment is calculated for IPMSM torque control.In order to ensure the accurate control,the change of motor parameters needs to be calculated into current trajectory control in each iteration of.Finally,the simulation model is established to verify the new control algorithm.