A series-LC-filtered active damper for ac power electronics based power systems

Abstract

This paper proposes an active damper with a series LC-filter for suppressing resonances in an ac power 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 power systems by the active damper.

Current control of grid converters connected with series ac capacitor

“…It is clear that V f can only be in the second or third quadrant in order to be sure that |V i | is lower than the grid voltage at PoC |V poc |. Further on, due to the 90̊ phase lead of grid current i L over the voltage V f , the allowed region of i L is thus limited to the third quadrant [12].…”

“…A lowfrequency transformer with the step-down or step-up functions is usually needed for these grid-connected converters, which increases the system volume and weight. The transformerless ac/dc power converter with a series-connected ac capacitor has recently been reported in hybrid active filters and dampers [4]- [7], [11], [12], and in distributed generation systems [8]- [10]. Fig.…”