Back-to-Back 31 Level Modular Multilevel Converter with EtherCAT Communication

The high number of submodules in the Modular Multilevel Converter(MMC) results in a superior output performance with a very small or no output filter requirement over any other converter topology. However, this advantage comes with a complexity in the control implementation due to multiple high speed processor requirement to generate the submodule gating signals and process the various information. Apart from each processor playing its own role, a high speed and stable communication is needed to synchronize the operation among them. A conventional high speed serial communication method can be established only with so many wire works and hardware devices that the probability of system failure happening is high. In this paper, EtherCAT communication method is explained and used in 31 level MMC system. EtherCAT is a robust communication method based on the industrial Ethernet technology. All the controllers, central controller and low level controllers, of the MMC system are connected in a sequence (daisy chain) and synchronized with processing MMC data through EtherCAT frame.