Control of a Modular Multilevel Converter With Reduced Internal Data Exchange

Modularmultilevel converters (MMC) are penetrating due to their superior performances. Due to the modular structure of the converter, communication platform has to be established between the submodules (SMs) and a central controller unit (CCU). When the communication platform is designed for such an application, several key parameters have to be considered such as high-speed data transfer with low propagation delay, data integrity, and ability for accurate synchronization. In order to minimize the data flow in the MMC, a hierarchical control is proposed where a CCU calculates an identical reference for all the SMs, while the modulation and capacitor voltage balancing is performed in the controller from the SM. Thus, at each sampling instance, only four bytes references are sent by the central controller to the controllers from the SM, while one or two bytes are received from SMs. Furthermore, the control algorithm is validated through experiments.