Application of optimal PWM of induction motor in synchronous machines at high power ratings

The proposed current harmonic model for high-power synchronous machines is dependent on the inductances of quadrature and direct axes. Variation of these parameters, as a consequence of modification in operating point, aging and temperature rise, in-progress pulse patterns, are no longer optimal solutions for minimization of harmonic losses. On the other hand, offline calculation of optimal pulse patterns for slight changes in these parameters, and storing them in read-only memories to serve as look-up tables, give rise to immoderate computational burden and unmanageable look-up tables. Notwithstanding performing online identification process and offline calculation of optimal pulse patterns, modification in switching scheme provokes transient condition which is a formidable task. In this study, we show that application of optimal pulse patterns of induction machine, whose total harmonic current distortion is independent of its parameters, is an appropriate alternative, provided that the deviation from minimum losses in a determined range is tolerable. Comparison results corroborate the efficacy of the proposed approach, particularly in high modulation indices.