Development of a Modular Multilevel Converter Demonstrator with EtherCAT Communication

The Modular Multilevel Converter (MMC) is a proven topology in HVDC, but it is also a suitable solution for medium voltage applications such as wind turbines. To increase the modularity and the scalability of this topology for medium voltage applications, a real-time communication bus between the submodules and the central control unit is implemented as an efficient way of control. This real-time communication is realized using EtherCAT communication. To verify the advantages of this control strategy a 3-kV 350-kVA demonstrator of a medium voltage MMC topology with EtherCAT communication is constructed and set up. The description and the analysis of this demonstrator with focus on the EtherCAT communication are presented in this paper. The communication path, the synchronization and the control including the modulation method are discussed, investigated and validated within this paper.