Design Strategy for Optimum Rating Selection of Interline DVR

This paper is concerned with calculating the optimum rating for two dynamic voltage restorers (DVRs) when used in an interline DVR (IDVR) structure. An IDVR consists of two or more DVRs which have a common dc link and, thus, can exchange active power. This can increase the compensation range of an IDVR compared with separate but otherwise similar DVRs. The basic operation of the DVR and IDVR is briefly explained. The limitations of IDVR operation in terms of active power exchange are explained and, based on that, the expressions governing the steady-state operation of IDVR are derived. The compensation range of an IDVR is compared with that of two separate DVRs. This paper also explores how the limitations in absorbing power from a healthy feeder can narrow the compensation range of an IDVR. After identifying and formulating various limitations in IDVR operation, a design procedure is presented to determine the optimum size (or rating) of the DVRs in an IDVR structure. In the proposed approach, all possible scenarios concerning healthy and faulty feeders are taken into consideration. Examples along with graphs and tables aid in conveying the proposed approach.