Uninterruptible power supply

Embodiments of the present disclosure relate to an uninterruptible power supply. The uninterruptible power supply comprises a switch, a power management module, an inverter and a controller. The switch is arranged between a load and a power source, the power source configured to supply power to the load. The power management module comprises a main energy storage and configured to reduce a ripple experienced by the main energy storage. The inverter is arranged between and coupled to the power management module and the load. The controller is coupled to the power management module, the inverter and the switch, the controller configured to control the inverter to regulate output voltage magnitude and frequency by regulating the power exchange between the inverter and the power source. According to embodiments of the present disclosure, the overcharging of the energy storage during sudden load rejections or utility phase jumps can be avoided.