State control of modular multilevel converters utilizing pole restraining

The modular multilevel converter (MMC) topology is characterized by excellent scalability. Converters with direct connection to high voltages in the range of several 100 kV can be built by stacking comparatively simple modules. The drawback of the technology is the single-phase structure, causing, among others, oscillations of the capacitor voltages which mainly depend on the AC currents. Therefore, dynamic control of MMC is still a challenge. A novel state-control approach is introduced using the pole-restraining control principle.