Hierarchical DC Current Balancing Strategy for Multilevel Current Source Converters Based on Differential Mode Sectional Power and Dual Redundant Vector Regulation

Unbalanced DC inductor currents in multilevel current source converters (MCSCs) can degrade power quality and potentially lead to overloading of individual modules or bridge arms. Traditional current balancing strategies either require extensive processing of redundant vectors or exhibit limited degrees of freedom, which increases complexity or directly affects current balancing performance. This paper proposes a novel hierarchical current balancing control strategy based on the analysis of differential-mode (DM) and common-mode (CM) components of DC currents. By adjusting the component aligning with the capacitor voltage in the module current reference, the AC DM-sectional power of the module is regulated, thereby balancing the DC DM components across modules. Furthermore, by adjusting the duration allocation ratio of two distinct zero vectors within the vector sequence of the module, the DC CM components are suppressed, ensuring balanced currents in the upper and lower branches. The proposed method is easily implementable, eliminating the need for complex redundant vector management and intricate multi-variable sorting, while introducing minimal additional switching frequency. Simulation and experimental results validate the effectiveness and superiority of the proposed strategy.