Importance

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Abstract

Series voltage compensation is provided in an ac power line by connecting the inverter unit of a dynamic voltage restorer (DVR) in series with the primary winding of a load transformer, which may already be present, thereby eliminating the need for injection transformers. For three-phase ac power lines the three primary phase windings can be either wye or delta connected. If they are wye connected, a three-phase inverter with a common dc source is preferred. For delta connected primary phase windings, separate single-phase inverters each with its own floating dc source can be directly connected in series with each primary phase winding. Preferably however, the poles of a two-phase inverter are direct connected in series between two of the primary phase windings and a common source phase, and share a common dc source referenced to the common source phase. While a single-phase inverter with its isolated dc source can be used for the third delta connected primary phase winding, it is further preferred that this single-phase inverter share the common dc source used by the two-phase inverter. In that case, one injection transformer is needed to isolate the compensation voltage inserted by this single-phase inverter in series with the third delta connected primary winding. Similar DVR arrangements can be used to provide series voltage compensation on the load side of a transformer with a delta connected secondary winding.

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