Analysis of communication based distributed control of MMC for HVDC

Modular Multilevel Converter (MMC) has gained a lot of interest in industry in the recent years due to its modular design and easy adaption for applications that require different power and voltage level. However, the control and operation of a real MMC consisting of large number of sub modules for high power and high voltage application is a very challenging task. For the reason that distributed control architecture could maintain the modularity of the MMC, this control architecture will be investigated and a distributed control system dedicated for MMC will be proposed in this paper. The suitable communication technologies, modulation and control techniques for the proposed distributed control system are discussed and compared. Based on the frequency domain modeling and analysis of the distributed control system, the controllers of the different control loops are designed by analytical methods and Matlab tools. Finally, sensitiveness of the distributed control system to modulation effect (phase-shifted PWM), communication delay, individual carrier frequency and sampling frequency is studied through simulations that are made in Matlab Simulink and PLECS.