A control scheme for utilizing energy storage of the modular multilevel converter for power oscillation damping

This paper presents a control scheme that utilizes energy storage of the Modular Multilevel Converter (MMC) for Power Oscillation Damping (POD) service. Such a service is used to enhance grid stability by providing damping power in the electromechanical (0.2-2Hz) dynamics range. The scheme uses compensated modulation with average energy control. The aforementioned service comes at the cost of additional energy storage requirement for the MMC. A worst case estimate of this additional capacity, together with potential options to obtain it, is also addressed in this paper. The scheme is validated by simulation studies on a four terminal HVDC test grid.