A synchronized sinusoidal PWM based rotor flux oriented controlled induction motor drive for traction application

This paper proposes a vector controlled induction machine drive with a wide field weakening zone. The proposed scheme integrates methods of field weakening, synchronized pulse width modulation, overmodulation and harmonic current estimation and proposes a consolidated scheme which ensures good dynamic response with wide speed variation. A triangular carrier comparison based Synchronized Sinusoidal Pulse Width Modulation (SPWM) for medium voltage inverters with low switching frequency (less than 500Hz) is proposed in this paper. To have very good dynamic behavior of the synchronization scheme, the triangular carrier is generated from the instantaneous voltage references in a phase locked manner. An overmodulation scheme which ensures linearity between the reference voltage and the fundamental motor terminal voltage is proposed. An inverse gain based linearization method is used to match the reference and inverter output voltage fundamental. This overmodulation strategy fails at the zone of high values of modulation index and a reference modification approach is used in that zone. The proposed PWM and overmodulation schemes integrate methods of field weakening and harmonic current estimation available in the literature and propose a consolidated scheme which ensures good dynamic response with wide speed variation for rotor flux oriented induction motor drive. The scheme is experimentally verified and the results are presented.