Research On Parameter Identification Based Maximum Torque Per Ampere Control For IPMSM

At present,more and more attention has been paid to the environmental protection,and energy-saving and emission-reduction has become the focus of attention in various industries.Air pollution and carbon dioxide emissions in cities caused by traditional automobiles have long been criticized by all social circles,so the automobile industry,the pillar industry of the national economy,is accelerating transformation towards electrification.Interior permanent magnet synchronous motor(IPMSM)has been widely used in electric vehicle drive system thanks to its high efficiency,high torque density,high starting torque,wide speed range and small size.Because the q-axis inductance of IPMSM is greater than to the d-axis inductance,the Maximum Torque Per Ampere(MTPA)control is often adopted below the base speed of the electric vehicle to make full use of the reluctance torque of the driving motor,improve the torque output capability of the driving motor.In this paper,MTPA control is deeply studied from two aspects: relying on motor parameters and independent of motor parameters.The core problems of two control algorithms need to be solved are analyzed,and the corresponding solutions are given.(1)In this paper,MTPA control based on motor parameters is studied.MTPA control strategy based on motor parameters is simple and easy to realize,and is the most widely used scheme in engineering field.However,under the influence of load change,motor aging,demagnetization and temperature rise,the parameters of the motor will change accordingly,which will reduce the dynamic and static performance and control accuracy of the MTPA controller algorithm.How to identify the direct axis and quadrature axis inductances and permanent magnet flux of permanent magnet synchronous motor accurately by model reference adaptive control(MRAS)is studied in this paper,and then the parameters of MTPA controller is adjusted to improve the control accuracy and torque output.(2)In this paper,two typical MTPA control strategies independent of motor parameters are studied.MTPA control based on search algorithm is studied.Under given load and speed,the optimal vector angle is searched online.By comparing the two stator vector currents,the search direction is determined,and the corresponding current vector angle of MTPA control is finally searched.In addition,MTPA control based on high frequency signal injection method is also st udied in this paper.By superimposing high frequency small amplitude current signal on stator current,and then detecting the response of input power to injection signal through signal processing,MTPA control vector angle can be locked.(3)In this paper,the search algorithm based on optimal judgment is further studied.the search algorithm needs to compare the electrical signal of front and back of two moments to determine the search direction,which inevitably leads to the search algorithm can not lock the optimal value,and the current vector angle will oscillate near the optimal value.For this reason,the search algorithm based on optimal judgment is further studied in this paper,which divides the search process into two intervals,not only accurately judges whether the search process reaches the optimal value interval,and can also accurately identify and stably output the optimal vector angle.So it could reduce the torque ripples and improve torque output.In summary,the control strategies of MTPA are deeply studied through simulation and experiment,The core problems of MTPA control algorithm based on motor parameters and search algorithm are analyzed,and the corresponding solutions are given.The MTPA control algorithm studied in this paper c an effectively solve the shortcomings of traditional MTPA control algorithm based on fixed motor parameters and search algorithm,and has good theoretical significance and engineering application value.