Renewable energy fed interline DVR for voltage sag mitigation in distribution grids

Two-line Interline Dynamic Voltage Restorer (IDVR) consists of two back-to-back Dynamic Voltage Restorers (DVRs) connected to independent distribution feeders with a common DC link. One of the involved feeders is feeding a critical load (critical feeder). When this critical feeder is subjected to voltage sag, its DVR will compensate this sag via voltage injection (voltage control mode). The voltage control mode may absorb active power from the DC link, so the other DVR will be responsible for maintaining a constant DC link voltage via pumping the required active power into the DC bus (power control mode). The maximum active power can be pumped from the healthy feeder is mainly depend on its load displacement factor. So, if the pumped power is not sufficient, the voltage restoration will fail. This paper suggests adding renewable energy sources as a support to this system, which may be coupled across the DC link to share, if needed, in supplying the required active power during voltage sag problem. Complete analysis supported with simulations is presented in this paper.