Research Of Selective Harmonic Analysis And Suppression On Permanent Magnet Synchronous Motor Vector Control System

The permanent magnet synchronous motor does not contain excitation coils,but relies on permanent magnet material excitation,which is a key difference between PMSM and electrically excited synchronous motor.There are many types of permanent magnet materials used in PMSM,in which the magnetic properties of rare earth materials including rare-earth cobalt and NdFeb are excellent.After several generations of development,the operation of PMSM is reliable and efficient,the structure without excitation coils has less loss,these outstanding advantages promote the wide application of PMSM in the fields including high-precision AC servo,electric vehicle drive,wind power generation,and marine electric propulsion.With the wide application of PMSM,the problem of high order harmonic in the stator current has been paid more attention by scholars.In PMSM vector control system,a series of high harmonic current will appear in the stator current of PMSM,with the highest content of the fifth-order and seventh-order harmonic,owing to the common effect of non-ideal conditions including air-gap field distortion of PMSM itself,the dead time added to the inverter circuit and the voltage drops of the power devices.The harmonic current components mixed with the fundamental phase current will not only cause more additional losses,generate a lot of heat and reduce efficiency of PMSM,but also destroy the output torque smoothness of PMSM,which will seriously restrict the use of PMSM in the high-level fields.Therefore,this paper makes the suppression of stator phase current high order harmonic on the PMSM vector control system as the focus.Firstly,this paper introduces the internal structure of PMSM,expounds the working principle of PMSM,derives the mathematical model of PMSM and the coordinate transformation matrix,analyzes the phase current of PMSM system based on vector control with the help of the fast Fourier analysis unit in Simulink,found that the fifth-order and seventh-order harmonic is much higher than other high harmonic components.Then this paper introduces the SVPWM that will be used in the PMSM vector control system and its implementation in Simulink.Next,the composition of the harmonic component of the phase current caused by different factors is quantified,and a method based on transformation of coordinates and current average method to extract the fifth-order and seventh-order harmonics on the PMSM vector control system is proposed,and harmonic control signal can be obtained through PI controller and transformation of coordinates,and then harmonic control signal can be put into current loop to compensate the harmonic.Finally,in the Simulink simulation environment,the algorithm module is introduced into the PMSM vector control system to compensate the specific fifth-order and seventh-order harmonic,the change of the PMSM phase current and output torque before and after compensation is compared and analyzed.