Comparison of direct and PWM model predictive control for power electronic and drive systems

In this paper, we compare the performance of the different Model Predictive Control (MPC) approaches for power electronic and drive systems: Finite Control Set (FCS) MPC directly applies the voltage vectors and Continuous Control Set (CCS) MPC uses voltage modulation (PWM, SVM). A unified system formulation is proposed to design both FCS-MPC and CCS-MPC for three-phase resistive-inductive loads with an internal voltage source. The controllers are implemented with the explicit MPC technique and they are evaluated with a permanent-magnet-synchronous-machine drive system. The steady-state performance is assessed in terms of current quality and switching frequency and the dynamic performance is evaluated estimating the control bandwidth. Although CCS-MPC and FCS-MPC have different characteristics (harmonic spectrum, constant or variable switching frequency, THD, etc.), they achieve similar performance. However, CCS-MPC can work with larger sampling-times, i.e. it has lower requirements on the control architecture. This makes it more versatile for application on different systems and power levels.