The Application of Optical Communication in the Sub-Module Design of Modular Multilevel Converter

With the sub-module number and scale growing on, the whole control system of MMC (Modular Multilevel Converter) tends to be much more complicated because of the cascade structure, which also intensifies the pressure of the converter main controller. To distribute the converter main controller’s task, the design of sub-module tenders itself extremely important. However, there is no explicit and comprehensive study on how to design the sub-module. This study, according to the characters of MMC, introduces a feasible architecture of hardware and software for the sub-module with optical communication. Each sub-module has its own independent controller and control system. That is to say, every sub-module is a complete system, which can do calculation and communication with outside. Sub-modules connect with the main controller of converter through communication using optical fibers. By adopting the optical communication, sub-modules not only can receive the control references data from the main controller, but also can send its own condition information back, which creates an interactive communication between the two sides. Additionally, through detailed experiments, the validity and feasibility of the design are demonstrated under two different control strategies.