Analysis and Trajectory Tracking Control of a Modular Multilevel Converter

The paper presents a control scheme for modular multilevel converters (M2Cs) where the property of differential flatness of the model of the load connected to the converter is exploited. This is done by encapsulating the subsystem of the load such that it appears in the model of the converter as a current source. The controller comprises a trajectory planning algorithm and a tracking controller. This way of modeling leads to a de-coupling of the controller for the load and the controller for the converter, especially for the design of the tracking controller. All developments rely on a single-phase model of an M2C, and it is shown that it shares the properties relevant for control design with the original three-phase model. All results are verified experimentally.