An uninterruptible power supply (UPS) includes a line terminal, a load terminal, a double-conversion circuit coupled in series, and further includes a bypass circuit, and a synchronize circuit. The line terminal couples to a doubly fed induction generator (DFIG). The load terminal couples to a load having a demanded power. The double-conversion circuit regulates grid power from the line terminal to the demanded power at the load terminal. The bypass circuit is coupled between the line terminal and the load terminal, and configured to deliver regulated power generated by the DFIG to the load terminal when the grid power is lost. The synchronize circuit is coupled between the double-conversion circuit and the DFIG, and, when the grid power is lost, the synchronize circuit injects a current through the double-conversion circuit and into the DFIG, synchronizing the regulated power generated by the DFIG to the demanded power.