Predictive current control of ac-ac modular multilevel converters

Multilevel converters can reach medium-voltage operation, increasing the efficiency in high power applications. Among the existing multilevel converter topologies, modular multilevel converter provides the advantages of high modularity, availability and high power quality. Moreover, the main advantage compared to cascaded multilevel converters is the absence of input transformer; reducing the size, cost and cooling requirements. When used as AC-AC converter, it usually requires a sophisticated controller to decouple the input and output frequency components. In this paper a predictive control approach is proposed to control a single-phase AC-AC modular multilevel converter. The controller minimizes the currents error and keeps the DC voltage balancing featuring a simple implementation, high input power factor and precise control of the output current. Moreover, the DC voltages are kept at the reference value. Simulation results showing the performance of the predictive control scheme are presented.