Modulated Model Predictive Control for Three-Phase Packed-U-Cells Multilevel Converter

Abstract

This paper proposes a Modulated Model Predictive Control (M2PC) algorithm for the three-phase Packed-U-Cells, PUC5, converter, that aims to minimize the output current error and balance the voltages of the DC bus capacitors. In order to do so, two cost functions are defined. The first one selects the sector in the SV diagram that minimizes the output current error, not taking into account the redundancies of the converter voltage vectors. After this, a second cost function for balancing the DC bus capacitor voltages is evaluated, considering only the voltage vectors of the chosen sector, including their redundancies. In this way, the proposed M2PC results in output voltages with fixed switching frequency, having a positive impact on the design of the output filter. Simulation results are shown, comparing the proposed M2PC and the standard variable frequency MPC strategies in terms of output current and voltage, internal capacitor voltage balancing and harmonic content.