Interline dynamic voltage restorer: a novel and economical approach for multi-line power quality compensation

Voltage deviations, often in the form of voltage sags, can cause severe process disruptions and result in substantial economic loss. The dynamic voltage restorer (DVR), a custom power device, has been proposed to protect sensitive loads from the effects of voltage sags on the distribution feeder. One of the main factors which limits capabilities of a particular DVR in compensating long duration voltage sags is the amount of stored energy within the restorer. This paper proposes a new concept of interline dynamic voltage restoration (IDVR) where two or more DVRs in different feeders are connected to a common DC-link. While one of the DVRs compensates for a voltage sag, the other DVRs connected to common DC-link replenish the DC-link energy storage. A current mode control strategy is incorporated into the IDVR system in both working modes, voltage sag compensation and power flow control. The reference voltage for power flow control mode is derived from instantaneous active current calculated using DC-link voltage error signal. Simulation results are presented for a simple system in order to demonstrate the efficacy of the proposed IDVR system.