Prediction Window Selection in FCS-MPC for Two-Level VSI Applications

Semiconductors in power converters are operated in switched-mode. For a given sampling frequency, a digital controller computes the next actuation according to several objectives. Typically one desires to regulate current or voltage values with minimal error and harmonic distortion. Higher switching frequency of the semiconductor is helpful as the granularity of the problem is improved and the harmonic spectrum is shifted toward high-order harmonics that are easier to filter with passive elements. However, the switching losses increase. Finite control set model predictive control (FCS-MPC) is proven to be an excellent control method with a great ability to maximize harmonic quality in terms of the switching frequency, particularly when the controller is configured to consider long prediction horizons. Nonetheless, in order to avoid computational overruns, the prediction horizon and the sampling frequency cannot be indefinitely increased. In this article, the tradeoff between these two parameters is studied, providing guidelines on FCS-MPC tuning for different configurations.