Predictive torque control of induction motor with integrated DC-link voltage optimisation

This study proposes a new method leading to a reduction in the current and torque ripple of an induction motor (IM) drive controlled by predictive torque control (PTC). The method lies within the optimisation of a DC-link voltage magnitude by the PTC cost function. Using a three-phase silicon-controlled rectifier, the DC-link voltage can be adjusted in such way that the current and torque ripple, caused mainly by treating the inverter as a source of only eight voltage vectors, is significantly reduced. The DC-link optimisation algorithm is integrated into the PTC that is used for the torque and flux control. In another prediction stage, the influence of the DC-link voltage on the torque and flux ripple is directly evaluated and then optimised by a second cost function. The theoretical analysis of the DC-link voltage influence on the drive behaviour is supported by simulation and experimental results conducted on a 5.5 kW IM drive, which confirm the benefits of the PTC with the DC-link voltage optimisation, especially if the drive operates in a region below the nominal speed.