According to one aspect, embodiments herein provide a UPS comprising a first input configured to receive input power, a second input configured to receive backup power, an output, a bypass line selectively coupled between the first input and the output via a bypass switch, wherein in a bypass mode of operation, the bypass switch is closed and the input power is provided directly to the output, an inverter comprising an input configured to receive at least one of the input power and the backup power and an output selectively coupled to the output of the UPS via an inverter switch, wherein in an online mode of operation, the inverter switch is closed and the inverter converts the input power into the output AC power, and means for operating the inverter to force commutate current in the bypass line after a transition from the bypass to the online mode of operation.