Five level neutral-point clamped inverter for a dynamic voltage restorer

DVRs are of utmost importance to secure sensitive loads from voltage sags. Especially, in medium-voltage grids the demand for securing larger loads has increased significantly. Installing higher power levels leads to the consideration of multi-level converters with an increased number of levels. Therefore, the 5-level NPC could be an interesting solution. The drawback of this topology is that its voltage levels are not stable for active power transmission. This paper presents a method to allow a short-time stable operation of this topology - without oversizing the DC-link capacitor - and therefore the usage of this converter for DVR applications