Research On The Dead-time Effect Suppression Of The Permanent Magnet Synchronous Motor System

Permanent Magnet Synchronous Motors(PMSM)are widely utilized due to their compact structure,high power density and high torque-current ratio.But the dead-zone induced by the inverters will lead to the torque ripple and current distortion,which will degrade the performance of the PMSM system and limit their application in the highprecision cases.A lot of research has been done on the torque ripple suppression,but seldom has been done on the harmonic current suppression caused by the dead-zone of the inverter.The current distortion of the motor will lead to the overheat problem,efficiency decrease and the result of the control strategy.So it's quite important to suppress the harmonic current caused by the inverter dead-zone.This paper concluded the principle of the PMSM,and built its mathematical model.Since there's not much particularly research on the PMSM system with the inverter dead-zone,the harmonic current mathematical model of PMSM with dead-zone was built.Some other parameters and state variables,which might influence the harmonic current caused by the dead-zone,including the PWM tuning mode,were also considered.In order to suppress the harmonic current caused by the inverter dead-zone,two kinds of controllers were designed.One was based on the specific harmonic wave suppression and the other one was based on all of the harmonic waves.To the second way,the dead-time effect was regarded as a periodic disturbance.A controller based on the Active Disturbance Rejection Control(ADRC)was utilized.Since there's no specific way to tune the parameters of the ADRC,frequency-domain was utilized in discovering the influence of the different parameters to the controller.The ability to suppress the harmonic current of ADRC was proved by mathematical deduction before designing the ADRC controller.The simulation results of ADRC were compared with the ones of PI controller,proving that ADRC could suppress the dead-zone effect.The optimization of the ADRC included three aspects: the optimization of the band of ESO;the optimization of proportionality factor of the input factor and the order of the controller,proving that1-order ADRC performed better in suppressing the current harmonic.The noise input was added to the feedback signal to test the robustness of the controller.As to the specific harmonic current suppression,the harmonic current injection was used to balance the harmonic current induced by the inverter.The rotation axis was induced first.When designing the filter,an average filter was designed to solve the confliction between the band and the speed of response in the 1-order digital filter.Feedforward control and cross coupling were induced to achieve a quicker and more precise control.The simulation results shows that the harmonic injection controller could achieve the suppression of the dead-zone effect.The content of 5th and 7thharmonic current were reduced significantly.A comparison was given between the ADRC and harmonic injection controller,along with all of the harmonic waves suppression and the specific harmonic wave suppression.On the basis of the theoretical analysis and simulation,with the help of the designed hardware experiment platform based on DSP,the above two control strategies were tested by experiment.The experiment results showed that these two control strategies could suppress the harmonic current caused by the inverter dead-zone and their feasibility were verified.