Research On Parameter Identification And Torque Control Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor(PMSM)is widely used in various driving and control occasions requiring high performance because of its high efficiency,high torque inertia ratio,wide speed range and other advantages.With the development of the electric vehicle industry,interior permanent magnet synchronous motor(IPMSM)with the characteristics of large torque and high speed is widely used in the electric vehicle industry.Because IPMSM has the characteristic of asymmetric rotor magnetic circuit,which can produce reluctance torque,it is necessary to design an appropriate maximum torque per ampere(MTPA)control strategy to make full use of the reluctance torque of the motor and improve the torque output efficiency and system efficiency of the motor.In order to control the PMSM with large torque stability.This paper studies the control strategy of MTPA considering the motor magnetic saturation,and puts forward some control strategies based on the research.First,this paper introduces the internal structure and mathematical model of IPMSM.Second,the mathematical model of IPMSM is transformed to DQ axis system by coordinate transformation,which makes us can use vector control to simplify motor control.Then the principles of different current control methods of PMSM vector control are introduced.According to the basic principle of MTPA control,the expression of the optimal stator current vector angle can be find by making the value of the motor torque equation takes the derivative of the stator current vector angle equals to zero.It is shown that the flux linkage and the inductances of the DQ axis will affect the optimal stator current vector angle,and then affect the control accuracy of the formula MTPA control.In this paper,an on-line inductance identification strategy of PMSM is studied.By applying a sinusoidal rotating voltage to the DQ axis voltage,the current response of PMSM will contain the signal components that reflect the inductance information.The corresponding inductance information can be extracted by digital signal processing.The results of inductance identification are used in formula MTPA control,and the control progress of formula MTPA control is improved.A calibration method of MTPA curve by d-axis current search method is studied.Under constant torque condition,the minimum stator current of current condition can be searched by using variable step to modify the given current of d-axis,besides the corresponding current value of DQ axis can be got,and calibrate the MTPA curve by repeatedly modifying the given torque value.A control strategy of maximum torque current ratio of IPMSM with virtual high frequency signal injection is studied.According to the formula derivation,a small high frequency sinusoidal signal is directly added to the detected motor current vector angle,and the mechanical power response of the calculated motor contains the signal component reflecting the torque change information.The corresponding power signal is extracted by signal processing method,and the optimal stator current vector angle is adjusted by PI controller,which helps to realize online MTPA control.On the basis of theoretical analysis,the above research strategies are simulated with Simulink simulation tools,and the correctness of the theory is verified.The hardware in loop simulation system based on DSP and RT-LAB realizes the MTPA control strategy.The hardware in loop simulation experiment is carried out with the Prius second generation motor as the object to further verify the effectiveness of the MTPA control method.