Research On Vector Control And Fault Tolerant Technology Of Six-phase Permanent Magnet Synchronous Motor For Electric Vehicles

Since the beginning of the 20 th century,with the continuous development and improvement of power electronic devices,inverters have been used more and more in many motor control systems.The use of inverters not only makes motor control easier,but also limits the number of motor phases.Compared with the traditional three-phase motor,it can be found that the torque of the multi-phase motor is smoother,and the system has the characteristics of multiple redundancy,so that the multi-phase motor needs high safety,low voltage,high power and high transmission ratio in ships,aviation,etc.More and more fields are used.This paper takes the six-phase permanent magnet synchronous motor as the controlled object,and conducts in-depth research on vector control and fault-tolerant control.This article first establishes the mathematical model of the six-phase permanent magnet synchronous motor,first analyzes the mathematical model of the six-phase permanent magnet synchronous motor in the natural coordinate system,and then follows the two different ideas of the dual three-phase motor and the overall six-phase motor.The mathematical model in the natural coordinate system is passed through different transformation matrices to finally obtain the motor model of the double d-q transformation and the motor model of the space vector decoupling transformation.Secondly,the vector control strategy of the motor is deeply studied.First,the established motor model is verified through traditional current hysteresis control.After that,the PWM algorithm of double zero sequence injection is used to control the six-phase permanent magnet motor.This method can obtain a centersymmetrical PWM waveform,and the number of switching times of each power device is fixed approximately once in each switching cycle.The voltage modulation range is the same as the four-vector SVPWM,and it is easier to implement hardware.Thirdly,the fault-tolerant control of the motor is studied.First,the magnetomotive force and torque of the six-phase permanent magnet motor during normal operation and when one phase is open are analyzed.Then,based on the principle that the magnetomotive force remains unchanged before and after the fault,two optimization schemes are proposed,which are the minimum copper loss and the torque.After the two schemes with the maximum output torque,the residual current is calculated according to different optimization schemes.In order to improve the current tracking performance,this paper adopts a new digital current hysteresis method,using the programmability of the digital microprocessor to reduce the peak value and improve the tracking performance.Finally,a dual-mode operating mode is proposed,so that the motor can select the operating mode according to different operating states.Finally,in order to experimentally verify the feasibility of the abovementioned control strategy,a verification scheme is proposed,and then the hardware and software part of the work is completed,and the experimental platform is finally completed,and the correctness of the control strategy is verified.