Research On Fault-tolerant Control Strategy Of Polyphase Permanent Magnet Synchronous Motor

With the continuous development of society,people put forward higher requirements for the reliability of motor systems in electric vehicles,ships,aerospace and other fields.Because the traditional three-phase motor drive system is difficult to meet the increasingly stringent requirements,and polyphase motor drive system has the characteristics of high power,high reliability and small output torque fluctuation,polyphase motor has received more and more attention.In polyphase motor control system,the fault of drive unit and sensor takes the largest proportion.When the drive system fails,it is difficult to meet the requirements of high precision control by using traditional PI controller to adjust the current loop;When the position sensor fails,the traditional control strategy cannot obtain accurate angle and speed information.Therefore,it is of great theoretical significance and practical value to study the key technical problems in the application of dual Y phase shifted 30 degree six phase permanent magnet synchronous motor,such as fault tolerant control,sensorless detection and deadbeat current control strategies.This paper first introduces the basic structure of the six phase permanent magnet synchronous motor,gives the mathematical models of the six phase motor in the static coordinate system and the rotating coordinate system,introduces the working mechanism of the space voltage vector and four vector modulation technology of the six phase inverter,and introduces the vector control strategy based on id=0.Secondly,the magnetic potential and torque before and after the fault are analyzed.According to the principle that the composite magnetic potential is unchanged,the amplitude and phase of residual phase current are obtained by using the optimal solution function in MATLAB with the minimum stator copper loss and maximum torque output as the optimization objectives respectively;In addition,the reduced dimension fault-tolerant control strategy is analyzed,that is,the six phase motor after the phase failure is regarded as a five phase motor,and the transformation matrix and the six phase PMSM mathematical model after the phase failure state are re deduced;At the same time,the quadratic coordinate transformation is introduced to reduce the coupling effect,and the MATLAB/Simulink software is used for verification and analysis.Thirdly,the technology of sensorless detection is studied.Aiming at the problem that the traditional back EMF method contains a large number of harmonic high-frequency signals at low speed,this paper proposes to use flux observer to obtain speed and position information.The estimated angle error parameter is introduced into the flux observer,the estimated speed feedback is used to improve the estimation accuracy,and the stator current frequency converter tracker is used to track the current frequency to reduce the current error;At the same time,in order to improve the estimation accuracy and the ability to resist disturbance of the observer,the rotor position error is taken as the disturbance term,and a third-order extended state observer is constructed through the mechanical motion equation of the motor to estimate the speed and rotor position,and a simulation model is built to verify the proposed algorithm.Fourthly,in order to improve the control effect after phase failure,a new deadbeat current prediction strategy is proposed.The problem of traditional deadbeat current prediction is that when the motor parameters and control parameters do not match,the steady-state performance of the motor system will be seriously affected.Therefore,an adaptive deadbeat current prediction model only related to the inductance parameters is proposed;At the same time,for the problem of control delay,the method of delay compensation is adopted to further eliminate the delay in the system control.the system simulation results verify the correctness of the proposed algorithm.Finally,taking 10 k W double Y phase shift 30 degree six-phase permanent magnet synchronous motor as an example,the system design and platform construction are carried out;The experimental results verify the correctness and feasibility of the proposed fault tolerant control strategy.