Model-Based Adaptive Control of Modular Multilevel Converters

Electrical power conversions are common in a large variety of engineering applications. With reference to AC/DC and DC/AC power conversions, a strong research interest resides in multilevel converters, thanks to the many advantages they provide over standard two-level converters. In this paper, we first provide a power-oriented model of Modular Multilevel Converters (MMCs), followed by a detailed harmonic analysis. The model is given in the form of a block scheme that can be directly implemented in the Matlab/Simulink environment. The performed harmonic analysis gives a deep and exact understanding of the different terms affecting the evolution of the voltage trajectories in the upper and lower arms of the converter. Next, we propose a new model-based adaptive control scheme for MMCs. The proposed control allows to determine the optimal average capacitor voltages reference in real-time, thus allowing to properly track the desired load current while minimizing the harmonic content in the generated load current itself.