Modular Multilevel Converters: State of the Art and Future Progress

Modular multilevel converters (MMCs) have paved the way for power electronics in very demanding application areas. While becoming the worldwide standard for high-voltage dc (HVDC), many other future applications are emerging. More and more, the functionality and cost of power electronics must be judged from a superordinate system view. Passive components "around" the converter, such as mechanical switchgear, fuses, overvoltage surge suppressors, and filters offer very low potential for future progress. With respect to protection, the scope must be widened from the semiconductors to the protection of the associated equipment (e.g., motors, drive trains, power net, and so on).