Central control and distributed protection of the DSBC and DSCC modular multilevel converters

The benefits of modular multilevel converters come at a price: Their high level of complexity demands for an intricate design methodology and a sophisticated control structure. This is especially true for converters that need to be able to recover from short-circuits, grid faults, communication faults or module faults. In order to build a reliable system, it is thus important to understand the effect that the control structure has on the converter design. When protecting each module against over-voltages and overcurrents individually, the performance of the central controller is no longer immediately safety critical. This allows to communicate the switching times and measurements with a daisy-chain-like communication architecture that does not require point-to-point connections from the central controller to every module. The presented approach is verified by time-domain simulations and validated on a downscaled hardware prototype system.