An uninterruptible power supply includes a rectifier coupled to an input of an uninterruptible power supply and converts a first alternating current having a first alternating current voltage to a direct current. An inverter is coupled to an output of the uninterruptible power supply and converts the direct current to a second alternating current having a second alternating current voltage. A bypass switch bypasses the rectifier and the inverter and provides a bypass power from the input to the output when in a bypass state. A control module switches the bypass switch to the bypass state when in a bypass mode and switches the bypass switch to a non-bypass state when in a UPS mode. The control module adjusts the second alternating current voltage between first and second voltage levels when in an adaptive voltage control mode after switching from the bypass mode to the UPS mode.