A simple modulation strategy for a Reduced Multilevel Converter using Predictive Control

Multilevel converters have many advantages in power electronics. This paper presents a new topology of multilevel converter based on flying capacitors that allows to increase the number of output voltage levels reducing the numbers of semiconductors necessary in comparison with the standard multilevel converters like Flying Capacitor Converter (FCC) and Stacked Multicell Converter (SMC). In particular, the proposed converter, Reduced Multilevel Converter (RMC), is an attractive choice as it can generate high quality output waveforms and reach high power levels. Several works have been presented in the literature for voltage capacitor balancing, relying on self-balancing properties for FCC and SMC. Nevertheless, the conditions for self-balancing operation cannot be guaranteed or achieved easily in the proposed multilevel converter. In this paper, a simple closed-loop scheme, based on Model Predictive Control (MPC), is used to properly modulate the converter output voltage in order to keep the capacitor voltages at the desired values. As the proposed modulation strategy regulates the capacitor voltages, fast linear controllers can be used for the current tracking, improving the dynamic behavior of the overall system.