A simple active damping method for Active Power Filters

Abstract

Active Power Filters (APFs) are widely applied devices in the power quality field for control flexibility and effective attenuation of the harmonic, reactive and negative components of the grid current and voltage. As the interface connecting an APF with the grid, an LCL-filter is preferred over an L-filter for its smaller size and lower price. However, the LCL-filter is a third-order system and hence causes stability problems by its resonance phenomenon. To suppress resonances, either active or passive damping methods should be conducted. Passive methods are simple but result in more energy loss and reduce system's efficiency. Meanwhile, active methods result in no energy loss but often require more sensors and complicate the controller. In this paper, a simple active damping method for APFs without additional sensors is proposed. The method is analyzed theoretically and verified with simulations and experiments.