Studying the performance of modular multilevel converter under arm voltage control during normal and faulty conditions

Modular multi-level converter (MMC) is one of the promising voltage source converter (VSC) topologies in recent years due to its modularity and scalability. Generally, the main technical challenge of different VSC topologies is the voltage balancing of sub-modules capacitors. Conventional sensor-based balancing techniques require a large number of voltage sensors which increases system cost and complexity. In this paper, a new balancing technique with a reduced number of voltage sensors is proposed. In the proposed technique, only one sensor per arm is needed (arm voltage control). The basic role of the proposed balancing technique is controlling the arm voltage to follow its instantaneous voltage reference by selecting appropriate combination from the available states of arm sub-modules. The proposed technique is tested during normal as well as abnormal operating conditions. A simulation model has been built to validate the proposed balancing technique.