A series-LC-filtered active damper for ac power electronics based power systems This paper proposes an active damper with a series LC-filter for suppressing resonances in an acpower electronics based power system. The added filter capacitor helps to lower the voltage stress of the converter to be used for implementing the damper. Unlike active filters for the compensation of low-order harmonics, the proposed active damper deals with the resonances caused by the interactions among grid-connected converters and reactive elements of the system, which are higher-order and vary in a wide frequency range. To confirm the validity of the damper, a three-phase experimental system is built, where the damper is integrated into a grid-connected converter. The results obtained from the experiments demonstrate the stability enhancement of ac power electronics based powersystems by the active damper.