Voltage quality improvement by a dynamic voltage restorer based on a direct three-phase converter with fictitious DC link

In this study, a new topology for a three-phase dynamic voltage restorer (DVR) has been proposed. The proposed topology uses direct three-phase to three-phase converter with fictitious DC link to compensate for the balanced and unbalanced voltage sags/swells and voltage flickers. The used converter in the structure of the proposed DVR has two inverter and rectifier parts with an intermediate fictitious DC link. The converter is directly connected to the grid and takes the required compensation power from the grid. As a result, the DC link capacitor and energy-storage elements have been eliminated in the proposed topology. Therefore the voltage compensation can be accomplished for any long time interval. This topology has less volume, weight and cost owing to the elimination of the energy storage elements. Unlike other direct AC/AC converter-based topologies, the proposed topology uses unidirectional switches instead of bidirectional switches, which results in the reduction in the number of switching devices. The computer simulation using PSCAD/EMTDC software and a laboratory-scale experimental prototype verify the capabilities of the proposed DVR in voltage disturbances compensation.