Research On Harmonic Elimination Technology Of Permanent Magnet Synchronous Motor System With Low Carrier Ratio

In recent years,high-power permanent magnet synchronous motor drive system has been widely used in the metallurgical,electric vehicles,subway traction and other industrial life,the power loss is mainly from the switching losses of the inverter switching device.Reducing the switching frequency can effectively reduce the switching losses,but for the traditional motor control strategy,the inverter output voltage harmonic content will increase,and the dynamic performance of the motor will be greatly affected.Aiming at the problems existing in the control of high power permanent magnet synchronous motor with low switching frequency,this paper proposes the Selective harmonic mitigation PWM to achieve the motor control,and the solving algorithm of its switching angles is studied.The main contents are as follows:Firstly,the mechanism of the three optimal PWM methods is analyzed,and the harmonic constraint equations are given respectively,including Selective harmonic elimination pulse width modulation(SHEPWM),Synchronous harmonic optimum pulse width modulation(SHOPWM),Selective harmonic mitigation pulse width modulation(SHMPWM).Aiming at the problem of poor dynamic performance of the motor with the optimal PWM,the method of realizing the direct control of the motor with the switching angle is given.Secondly,based on the harmonic constraint equations of the three optimal PWM methods,the solving algorithms of switching angles is studied,including the traditional particle swarm optimization algorithm,genetic algorithm,and the proposed Differential Evolution with Composite Trial Vector Generation Strategies and Control Parameters(CoDE).The theoretical research and implementation of the above algorithms are carried out respectively.After comparing the results,the advantages of the proposed algorithm are expounded.Thirdly,based on the problem of poor dynamic performance of the optimal PWM,the hybrid modulation technique is proposed to meet the dynamic and static performance of the system.Change the motor speed with SVPWM and maintain the speed with SHMPWM.And the simulation research is carried out to verify the validity and feasibility of the hybrid modulation technology.Finally,the experimental platform of the control system is constructed,and the performance of the optimal PWM modulation algorithm is studied.And the the experiment of permanent magnet synchronous motor(PMSM)under low carrier ratio is studied with SHMPWM,The proposed control strategy is mainly evaluated from the harmonic content of the inverter output voltage and the motor current,the dynamic characteristics of the motor and the running stability.