Finite-control-set model predictive control with a fixed switching frequency vs. linear control for current control of a single-leg inverter

In this paper a finite-control-set model predictive control (FCS-MPC) scheme for achieving a fixed switching frequency is compared with a linear regulator for current control of a single-leg inverter driving a resistive-inductive load with a back-EMF. This comparison is motivated by the fact that finite-control-set MPC is often regarded as having an inferior output waveform quality compared to PWM due to a variable switching frequency. In this paper, an oversampled FCS-MPC control scheme that achieves a fixed switching frequency through hard constraints is compared to an oversampled and well-tuned linear resonant regulator. It will be shown that by oversampling the predictive controller and forcing a fixed switching frequency scheme, the output waveform quality of FCS-MPC can produce results similar to that of a PWM-based controller. It will further be shown that the typical one-sample delay during reference step changes and the effects of model uncertainties such a DC bus ripple are greatly reduced if the predictive controller is sampled at a much higher rate than the switching frequency.