| Multiphase permanent magnet synchronous motors have the advantages of low voltage,high power,small torque fluctuations,good speed regulation performance,and strong fault tolerance,and are widely used in fields such as ship propulsion,rail transit,aerospace,and so on.The rotor position,as an essential feedback variable for controlling multiphase permanent magnet synchronous motors,is usually obtained using mechanical sensors such as photoelectric encoders and rotary transformers.However,in some special envoy situations,such as ship shaftless thrusters and bearingless motors,mechanical position sensors cannot be installed,and the acquisition of rotor position can only be achieved through sensorless control technology.Therefore,the position sensorless control technology of multiphase permanent magnet synchronous motors has become a research hotspot.Sensorless control technology has significant advantages over mechanical position sensors in terms of cost,space,weight,reliability,integration,power density,and adaptability to working conditions.Therefore,rotor position detection technology with low cost,high reliability,and no dependence on traditional position sensors has become a research hotspot at home and abroad.Therefore,this article conducts research on the rotor position estimation method of a six-phase permanent magnet synchronous motor based on auxiliary coils.Firstly,the mathematical model of the six-phase permanent magnet synchronous motor was established,the air gap magnetic density of the auxiliary coil was analysed and the induced potential of the auxiliary coil was derived.The corresponding Matlab/Simulink simulation model is also built according to the mathematical model and the theoretical simulation is verified.Next,the rotor position estimation method based on the conventional phase-locked loop is introduced and its rotor position error function is analysed.In view of the poor filtering effect of the conventional phase-locked loop,an adaptive filter is designed to pre-process the auxiliary coil induction signal and improve the signal-to-noise ratio of the signal.The rotor position estimation method based on the improved phase-locked loop is also designed according to the mathematical model of the motor,which solves the problem of non-convergence of the error function of the traditional phase-locked loop.Finally,the corresponding Matlab/Simulink simulation model is built and the theoretical simulation is verified.Again,the overvoltage of a six-phase motor Si C inverter driving a resistive load such as a motor through a critical length of cable and the mechanism of overvoltage oscillation generation are analysed.The effects of the inverter bus voltage and the length of the supply cable between the inverter and the motor on the overvoltage of the resistive load are further analysed.Based on the overvoltage generation mechanism,an adaptive quasi-three-level PWM modulation method is used to suppress the overvoltage and reduce the overvoltage amplitude at the resistive load from 3 times the DC bus voltage to1.2 times the DC bus voltage,while reducing the high frequency noise in the load current and thus the induced noise signal in the auxiliary coil.Finally,in order to verify the correctness of the rotor position estimation method,a six-phase permanent magnet synchronous motor drive system is designed according to the experimental requirements and some of the main circuit design ideas and schematics are given.Then,the software control program was developed jointly by Matlab/Simulink and CCS according to the inverter control and experimental requirements.Finally,experiments are carried out on a six-phase permanent magnet synchronous motor based on a modified phase-locked-loop rotor position detection method with an auxiliary coil.The results demonstrate that the improved phase-locked loop-based rotor position estimation method has better accuracy and stability than the conventional phase-locked loop-based rotor position estimation method. |
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