Protection schemes for a dynamic voltage restorer

Grid-connected applications of power electronics, as dynamic voltage restorers and uninterruptible power systems require special attention in the concept and design of the protection scheme, since the equipment can be subjected to severe disturbances during abnormal conditions, such as voltage surges and short-circuits. This paper discusses the main aspects involved in the protection of a dynamic voltage restorer against this kind of abnormal conditions. Although focusing on the protection of a dynamic voltage restorer, many of the presented methodologies can be readily applied in the protection of other power electronics-based equipment, connected to the utility grid. A full-scale prototype of a dynamic voltage restorer (440 V/500 kVA) is used as a case study to illustrate the proposed methodologies. In addition, experimental results obtained with a small-scale prototype (5 kVA/220 V), are included to allow the evaluation of the proposed methodologies.