Research On Suppression Method Of Rotor Position Estimation Error Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor(PMSM)position sensorless control technology can reduce the size and cost of the motor,which is research hotspot in the field of motor control.However,because the motor is effected by the non-linear effects of the inverter and the space harmonics of the magnetic field,harmonic components appear in the stator current,which further leads to harmonic components appearing in the back electromotive force(EMF),ultimately results harmonic errors in the rotor position value estimated by the traditional sliding mode observer(SMO).In addition,a DC offset error due to the delay of the low-pass filter(LPF)of the SMO will appear in the estimated rotor position.The rotor position error will cause the motor torque ripper,and increasing additional losses.In order to reduce the error and improve the control accuracy of the system,this paper studies the harmonic suppression strategy and the DC offset error suppression method.Firstly,the mathematical model of the PMSM under ideal conditions is derived.Then,this paper analyzes and deduces the production process of the harmonic error and the DC offset error in the rotor position estimation obtained by the SMO combined with the extended back-EMF model.Secondly,in view of the inverter output voltage error and stator current harmonic problems caused by the inverter nonlinearity effect,an inverter nonlinearity compensation strategy is proposed.This compensation strategy first observes the error value of the inverter output voltage and the given voltage through the disturbance observer online.Takeing the zero current clamping effect into account,the compensation voltage is obtained by correcting the voltage error through the gain correction function.Finally the compensation is performed on the inverter,thus,the output voltage error of the inverter and the harmonic content in the three-phase current are reduced,the harmonic error of the estimated rotor position are reducd.This compensation strategy can update the compensation voltage in real time.Simulation shows the strategy is valid.Thirdly,aiming at that as the speed increases,the influence caused by the inverter nonlinearity decreases,and the inverter nonlinear compensation effect will be weaken,and the DC offset error caused by the delay of the low-pass filter is not suppressed,this paper proposes a multi-specified harmonic adaptive filter structure,based on the improved second-order generalized integrator(SOGI).The filter can filter out the 5th and 7th harmonics in the estimated back-EMF,reducing the harmonic error of the rotor position estimation error,track the fundamental frequency of the back-EMF in real time during the variable speed regulation process,and suppress the rotor position DC offset error.The filter significantly improves the accuracy of the estimated rotor position value.Finally,in the position sensorless control system,the combination of the inverter nonlinear compensation strategy and the multi-specified harmonic adaptive filter,jointly improve the accuracy of the rotor position estimation information and ensure the stability of the motor.Through the PMSM experiment platform,the experimental results of the two methods under different motor conditions are compared and analyzed.The results illustrate the combination of two methods effectively suppresses the rotor position estimation error,and the accuracy of the rotor position information and the control performance of the PMSM sensorless system are improved.