Modeling and Design of Internal Energy Balance Controller with Circulating Current Suppression for Modular Multilevel Converter

This paper provides an in-depth investigation of the modeling and design of an internal energy balance controller for MMC in the context of a three-phase grid-connected converter. Given the inherent complexity of MMC's internal dynamics, this paper aims to address the critical challenges associated with the transient performance, including high circulating currents, which are prevalent under open-loop operation. The proposed energy balance controller has been designed to ensure that the energy distribution remains balanced across the submodules (SMs), thereby significantly enhancing the transient performance and reducing the circulating currents. A mathematical model of the energy balance controller has been developed, with a detailed analytical foundation for its implementation and design. The controller's performance is assessed through a simulation study in MATLAB/Simulink.