Model-based cascade control of single-phase Modular Multilevel Converters ideal reference

Electrical power conversions are common in a large variety of engineering applications. With reference AC/DC and DC/AC power conversions, a strong research interest resides in multilevel converters, thanks the many advantages they provide over standard two-level converters. In this paper, a power-oriented model single-phase Modular Multilevel Converters (MMCs) is first provided, followed by a detailed harmonic analysis. The model is given in the form of a Power Oriented Graphs 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 converter. Next, a new model-based cascade control architecture for MMCs is proposed. Combined with real-time calculation of the ideal average capacitor voltages reference, the proposed control architecture allows to properly track the desired load current while minimizing the tracking error and the harmonic content the generated load current itself.