Design and simulation of a modular multi-level converter for MVDC application

A modular converter structure for medium voltage DC (MVDC) applications is presented in this paper. The new converter structure is designed in such a way that, the modularity is available not only for voltage but also for current ratings, using the available devices. The new converter will be applicable for a wide range of medium voltage applications and using its modularity it also can be scaled up for high voltage applications. The proposed-converter control is described and the overall operation is explained through simulation. A simple active-reactive power control is utilized for the converter control. It has been highlighted, through simulation, that the proposed converter has a high degree of design flexibility introduced by its high number of redundant switching states. These redundancies are implemented for controlling the capacitor voltages of the converter modules. More importantly, they provide the converter with a DC and AC sides fault-handling capability; a function that is essential for an MV converter. It is explicitly shown that the converter can provide ancillary services to the grid during DC faults.