Constant v/f induction motor drive with synchronised space vector pulse width modulation

Three-level voltage source inverters are preferred for high-power variable speed drives. Owing to low switching frequency the inverter output voltage will be rich in harmonics. The synchronised space vector pulse width modulation (SVPWM) guarantees half-wave, quarter-wave and three-phase symmetry in the output voltages, resulting in improved harmonic distortion even at low switching frequency. This study presents the experimental implementation details of the synchronised SVPWM algorithm for the complete operating region of the drive including the overmodulation region and six-step operation. The synchronised SVPWM is applied and tested on a constant v/f induction motor drive powered from a three-level cascaded H-bridge inverter. The performance of the algorithm at transient and steady-state conditions are studied. The experimental results are presented.