Abstract

The modular multilevel matrix converter (M3C) is an ac to ac power converter composed of 9 arms and is proposed for high power applications such as motor drive and wind energy conversion systems. Energy Control of the M3C is achieved using four circulating currents, and is frequently divided into the different frequency mode (DFM) and equal frequency mode (EFM). EFM is more challenging, because of the larger capacitor voltage oscillations that can be produced. The control schemes are typically different for EFM/DFM operation and this further increases the complexity. In this article, a continuous-control-set model predictive control for energy management of the M3C is proposed. The control scheme is based on solving an equality constrained quadratic programming problem, where the optimal solution is analytically obtained. The result is a single and simple control law to obtain the circulating current references, where good performance is achieved for both EFM and DFM. The proposed strategy is experimentally validated using a scaled-down M3C prototype composed of 27 power cells.