A model-based controller for a three-phase grid-connected modular multilevel converter

This paper presents the modelling and control of the three-phase grid-connected modular multilevel converter. Based on the obtained model, a combined controller is proposed with the aim to regulate and balance the total energy on each converter phase, minimize circulating currents, and inject a current in phase with the grid voltage. For this, the proposed controller builds a reference for each arm of the modular multilevel converter, which then can be used in a proper modulation scheme to obtain the switching sequence for each submodule of the converter. Numerical results are presented to validate the proposed control scheme.