On the Benefit of Long-Horizon Direct Model Predictive Control for Drives with LC Filters

Even though direct model predictive control (MPC) schemes almost exclusively use a prediction horizon of one in power electronics applications, the use of longer horizons offers significant performance benefits. This statement is underlined in this paper for a medium-voltage variable speed drive system, which consists of a three-level inverter, an LC filter and an induction machine. The proposed MPC controller simultaneously regulates the inverter current, capacitor voltage and stator current along given references, by manipulating the switch positions of the inverter. As will be shown, extending the prediction horizon significantly reduces the oscillations due to the filter resonance. For sufficiently long horizons, such as ten, low total harmonic distortions of the stator current can be achieved at low device switching frequencies. An additional active damping loop is not required, adding to the conceptual simplicity of the proposed control scheme.