Model Predictive Direct Torque Control of a variable speed drive with a five-level inverter

Model predictive direct torque control (MPDTC) is a newly developed computational control method for medium-voltage drives, which, based on the principles of model predictive control, reduces the converter´s switching losses and improves the torque´s total harmonic distortion (THD) with respect to standard direct torque control (DTC), while maintaining DTC´s favorable dynamic and robustness properties. In this paper, MPDTC is adapted and applied to a five-level converter driving a high frequency induction machine. This application poses the challenge to produce five-level waveforms within the (short) fundamental period while respecting the converter´s thermal limitations. The MPDTC methodology is tailored to the specific application by decomposing the controller into a machine and three phase controllers. Initial results suggest that, with respect to pulse width modulation (PWM), MPDTC is capable of simultaneously reducing the switching losses and the torque THD, both by roughly 50 %.