CAN-based distributed control of a MMC optimized for low number of submodules

In recent years, the Modular Multilevel Converter (MMC) has gained a lot of interest in industry due to its modularity and scalability for different power and voltage levels. However, the control of a MMC consisting of several submodules is often implemented in a central control system, so that the whole MMC system cannot be considered as modular. The thought to distribute control tasks to each submodule arises. Therefore, high speed serial communication protocols such as EtherCAT and CAN have been proposed. This paper presents a distributed control of a scaled MMC test bench using the CAN communication protocol. We are focusing on medium voltage applications using phase shifted PWM technique. Voltage balancing control implemented as state machine optimizes the sort and select balancing method for a MMC with a low number of submodules. A solution for the synchronization of the control modules is also presented.