Generalized Control Approach for a Class of Modular Multilevel Converter Topologies

This paper presents a generalized control concept that can be applied to a class of modular multilevel converter topologies. Examples for such topologies are the Modular Multilevel Converter, the Modular Multilevel Matrix Converter, and the Hexverter. The presented control approach consists of a current control based on the state-space representation and a branch energy balancing control. For the branch energy balancing, an optimization process leading to minimal additional current stress is presented. After describing the control approach in general form, it is applied exemplarily to the Modular Multilevel Matrix Converter. A comparison with the branch energy balancing for the Modular Multilevel Matrix Converter from previous publications is conducted, which shows the improvement achieved by the presented control. In fact, the previously published controllers are boundary cases of the presented optimized solution. The generalized control concept is verified by simulation and experimental results for the Modular Multilevel Matrix Converter. It can be easily applied to new configurations.