Errors of a Linear Current Approximation in High-Speed PMSM Drives

Current sampling techniques and predictive algorithms used in the digital control of electric drives rely on a simple mathematical model that assumes linear current changes upon constant supplying voltages. This paper identifies rotor movement as a factor that makes this assumption invalid when the rotor covers an angular distance of a few tens of degrees during the control interval duration. The errors of the linear current approximation were quantified both by simulation and by experiment for an exemplary high-speed permanent magnet synchronous motor drive.