Research On Vector Control Of Multi-level Permanent Magnet Synchronous Motor

Medium-high voltage motor occupies a large proportion of the whole motor field,so it also promotes the development of multi-level high-voltage frequency converter industry.The system composed of multi-level high-voltage frequency converter and high-voltage motor is an important part of the industrial control system.In metallurgy,petrochemical,electric power industry and other industries have a wide range of applications.Compared with high-voltage asynchronous motor,high-voltage permanent magnet synchronous motor has obvious advantages,such as high power density,high efficiency and high power factor,so it will have better energy-saving effect when variable-frequency speed regulation of high-voltage permanent magnet synchronous motor is carried out.Based on this,the system composed of multilevel high voltage converter and permanent magnet synchronous motor(380V system)is studied in this paper.First of all,the type of multilevel converter is cell series multilevel converter in this paper,and the unit mainly considers the control of the inverter side,and the bus voltage is default to the constant value,and the modulation mode of the inverter side adopts the bipolar carrier phase-shift modulation strategy.Afterwards,in the high power drive system,in order to reduce the switching loss,the switching frequency of the inverter is usually not too high,which not only limits the bandwidth of the current loop,but also leads to a large delay in the control loop,on the other hand,the cross-coupling of the dq axis voltage of the permanent magnet synchronous motor will also be increased and the performance of the current loop will be further reduced.In view of this,a complex vector current controller is designed in this paper to further improve the performance of the system.In the next place,the speed loop is usually controlled by PI in vector control,but this control mode is affected by the parameters of the motor,when the parameters of the motor are changed for a long time,the system will have the problem of poor robustness of the parameters.In this paper,the sliding mode controller is designed to improve the shortcomings of the PI controller,and the traditional sliding mode controller is improved,a global fast Teminal sliding mode controller is introduced to eliminate the inherent chattering phenomenon.Once more,this paper studies the speed sensorless vector control strategy of permanent magnet synchronous motor:the I/F is studied at low speed;the model reference adaptive and back EMF correction method is studied at medium and high speed,and the operation of the speed sensorless in the full speed range of the permanent magnet synchronous motor is realized through a smooth switching strategy.Finally,the three-unit cascade H-bridge inverter,complex vector current controller,global fast Terminal sliding mode controller and speed sensorless control of permanent magnet synchronous motor are integrated,and the whole system is preliminarily verified by MATLAB simulation and experiment.