An uninterruptable power supply system is disclosed with a precharge converter for connecting to a DC link of the uninterruptable power supply system to a DC power supply, whereby the DC link comprises a first and a second DC bus line, which are both coupled to a common reference point, whereby the common reference point can be an AC power supply neutral of the uninterruptable power supply system, comprising power connectors for connecting to the DC power supply, a first and second output connector for connecting to the first and the second DC bus line, respectively, a converter circuit for receiving DC power from the power connectors and providing DC power to the first and second output connector, and a control unit for controlling operation of the converter circuit.