Research On Control System Of High Speed Permanent Magnet Synchronous Motor Based On Multilevel Inverter

High-speed Permanent Magnet Synchronous Motor(PMSM)has many advantages that the constant speed Motor cannot match: small moment of inertia,high power density,small volume,high efficiency and fast dynamic response,so it has been widely applied in high precision machining and high performance machinery.As the speed of high-speed PMSM is much higher than that of constant speed motor,the current frequency of the motor winding is also higher than that of the constant speed motor.Therefore,the current harmonic content of the inverter driving the motor is also higher than that of the constant speed motor,which has a great impact on the operation efficiency and torque stability of the high-speed PMSM.In order to improve the performance of the control system of the high-speed PMSM the research on the harmonic suppression method of stator current of the high-speed PMSM is particularly important.In addition,the sensors applied to rotor speed detection of high-speed PMSM is rare,thus the sensorless technique is needed in most cases to estimate rotor speed.So it is of certain theoretical and application value to develop the research on sensorless technique for high-speed PMSM.This paper will mainly probe into some key techniques applied in the high-speed PMSM's control system,such as stator current harmonic suppression and sensorless technique.The main research contents are as follows:Firstly,in this paper,three rotor structures of PMSM are described in this paper,and mathematical models of PMSM are established respectively in three-phase static ABC frame,two-phase static DQ frame and two-phase rotating dq frame.The torque and flux estimation principle of PMSM are described as well.The Direct Torque Control(DTC)method of PMSM is introduced.Secondly,in view of the high current harmonic content of high-speed PMSM,the algorithm for simplified three-level Space Vector Pulse Width Modulation(SVPWM)is studied in depth,the vector synthesis principle and realization process of the traditional three-level SVPWM algorithm are introduced,the advantages and disadvantages of traditional SVPWM are analyzed,a simplified three-level SVPWM five-stage vector synthesis algorithm based on the decomposition of reference voltage vector is proposed,which further simplifies the complexity of SVPWM algorithm and makes it suitable for high-speed PMSM control system.A simulation model is built to compare the performance of the two algorithms.Finally,the sensorless control method for high-speed PMSM is studied,the principle of Luenberger observer is introduced,the problem of the traditional observer algorithm is improved by adding relation function to correct the observed speed deviation in the traditional observation algorithm.A simulation model of DTC system for high-speed PMSM based on Luenberger observer is built in Matlab/Simulink and the simulation of the PMSM at various speeds is carried out.The simulation results verified the correctness and feasibility of the improved method.