Low Speed Performance Improvement Using Selective Synthetic Voltage Vector in Predictive Direct Torque Control IM Drive

In direct torque control induction motor drive, low speed performance is deteriorated due to demagnetisation effect. In predictive torque control (PTC) or predictive direct torque control, low speed operation greatly affects the torque and flux ripples with high harmonic distortions in the current. In conventional PTC, low speed performance is improved by synthetic voltage vectors at the expanse of higher switching frequency and longer computation time. This paper presents the predictive direct torque control with selective synthetic voltage vector to provide improvement in switching frequency, current THD, torque and flux ripple from low to rated speed range. This algorithm provides appropriate choices between the active and synthetic voltage vectors based on the flux location and deviation to compensate the demagnetisation effect. This algorithm is tested on the laboratory prototype to verify the 3-phase induction motor drive performance.