Constrained MPC for Intercluster Energy Control of Modular Multilevel Matrix Converters

This article presents a circulating current reference generator based on a constrained model predictive control approach to perform the intercluster capacitor voltage balancing in modular multilevel matrix converters (M3C). The proposed reference generator incorporates nominal current limits as bound constraints into the optimal control problem. This approach enables the reference generator to efficiently provide the necessary circulating current in each cluster, thereby balancing the energies of the converter's clusters. As a result, the M3C can operate even during critical frequency points, significant power steps, and severe imbalance levels while ensuring that every cluster current remains within its feasible limits. Experimental results on a M3C prototype of 36 submodules are provided to validate the effectiveness and high-quality performance of the proposed strategy.