Research On Current Harmonic Suppression Of PMSM Based On SiC Inverter

The third-generation wide-bandgap SiC power devices are widely used in PMSM(permanent magnet synchronous motor)control systems due to their advantages of fast switching speed,high power density,low loss and high thermal conductivity to achieve high-efficiency and low-noise drive.Compared with the traditional silicon IGBT,the new SiC MOSFET can significantly increase the switching frequency,improve the sampling and control accuracy,in addition to the smaller dead time,and higher efficiency.Therefore,in order to improve the control performance of PMSM and reduce current harmonics,this paper mainly focuses on the drive control strategy and current harmonic suppression technology of PMSM based on SiC MOFET inverter.The specific research contents are as follows:Firstly,the basic mathematical model of PMSM is established,and the vector control strategies widely studied at present are analyzed.With vector control as the core control algorithm,the static decoupling of the d-q axis current can be realized.In order to solve the digital control delay problem caused by the dynamic coupling of the d-q axis current and improve the current control accuracy,the complex vector mathematical model of PMSM is derived.Based on the traditional PI controller design method,a complex vector digital current regulator is designed by the discrete domain direct design method,which improves the dynamic performance of the controller at high speed conditions.Secondly,by analyzing the switching process of SiC MOSFET and the influence of SiC parasitic parameters on the switching process,this paper provides a theoretical basis for the subsequent hardware circuit design.Aiming at the aggravation of dead zone effect at high switching frequency of SiC inverter,an effective dead zone compensation measure is proposed.By improving the dead zone compensation algorithm,the problem of poor current polarity detection accuracy caused by current zero-crossing distortion is solved,and it has better dead zone compensation effect.At the same time,in order to simplify the implementation of the algorithm and reduce the calculation delay,an improved dead zone compensation strategy based on zero-sequence component injection method is designed by combining the SVPWM normalized scalar modulation strategy.Thirdly,in order to realize the effective suppression of the low-frequency 5th and 7th current harmonics in the stator current and reduce torque ripple and vibration noise,the generation mechanism of current harmonics is analyzed,and the current harmonic suppression algorithm based on proportional resonance controller is studied.Meanwhile,in order to solve the problem of poor current harmonic suppression effect caused by fixed resonance parameters in the full speed range,the parameter design method of the proportional integral resonance controller is optimized and improved,and the stability of the discrete control system is proved according to the second Lyapunov method sex.The effect of suppressing the current harmonics before and after the improvement of the proportional integral resonant controller is compared in the simulation.Finally,in order to improve the control accuracy of the system,DSP digital controller is adopted to implement the algorithm,and SiC MOSFET is used as the power component of the inverter to increase the switching frequency of the inverter.In order to simplify the digital implementation process of the control algorithm and save time and cost,the control system software is designed through Simulink code generation technology based on the model design.Moreover,the experimental test platform is built to verify the feasibility and effectiveness of the proposed methods.