Research Of SVM-DTC System For Permanent Magnet Synchronous Motor Based On Variable Cutoff Frequency Trapezoidal Discrete Flux Observation

Permanent Magnet Synchronous Motor(PMSM)has numerous excellent performance,and is a key energy conversion equipment in modern industrial production,and is widely used in new energy vehicles,intelligent robots and other fields.Therefore,it is very necessary to choose the appropriate control methods to improve the performance of PMSM.Direct Torque Control(DTC)is a commonly used PMSM control method.Hysteresis controller is used in traditional DTC control,which makes the system torque and flux ripple too large.In order to solve the problem of large torque and flux ripple,this paper introduces space vector modulation into the DTC system to form SVM-DTC system,which can effectively reduce the flux and torque ripple.This thesis conducts the research based on the SVM-DTC system,and the main contents are as follows:(1)Aiming at the problem of power consumption during the operation of the permanent magnet synchronous motor,an approach of given changing reference flux linkage,which reasonably regulates dq currents to produce the desired torque with the minimum stator current,is further introduced to achieve the optimal control of the stator current so that the motor efficiency is improved.The simulation results prove that a system with a given changing reference flux produces smaller current values than a system with a constant reference flux.(2)In order to solve the problem of poor anti-interference ability of the permanent magnet synchronization motor in the SVM-DTC system,the speed loop adopts the active disturbance rejection controller(ADRC)to replace the traditional PI controller,and reduces the burden of the ADRC through introducing the load observation to feedforward compensation on the speed loop.The simulation results show that the speed loop compensation active disturbance rejection controller can not only improves the anti-interference ability of the SVM-DTC system,but also effectively reduces the speed overshoot of the system output.(3)The stator flux observer is the key part of SVM-DTC system,however,the conventional voltage-based flux linkage observer fails to remove the bias component of the back electromotive force,which leads to the issue of DC accumulation.In this paper,by adopting a new voltage model,the issue of DC accumulation is effectively solved,furthermore,following the analysis of the influence of frequency abrupt change on the output flux linkage,this paper exchanges the amplitude phase compensation link and the filtering link to enhance the dynamic performance of the system.Considering the change of electric angular velocity during motor operation,it is necessary to set the cutoff frequency of the observer to change with the change of electric angular velocity,so that the bandwidth of the observer is in a reasonable position.At the same time,considering the accuracy of the backward integral discrete method,in order to further improve the observation accuracy of the observer,the trapezoidal discrete method is used for discrete processing,thus a trapezoid discrete flux observer with variable cutoff frequency is proposed.The simulation results show that the electromagnetic torque and stator flux observed by the system have high precision,and the maintained the stability of flux linkage in the case of offset under the condition of induced electric motive force and has good dynamic response performance.(4)Finally,a test bench was built for verification.The experimental results showed that the flux and torque waveform observed by the system fluctuated very little,and the flux waveform was stable without deviation.The output current value of the system was small,the motor speed fluctuation was small,and the stability of the whole system was high.