Patent ID: 8552589

Claim:
An uninterruptible power supply configured to operate in parallel with a second uninterruptible power supply in a power distribution system, the uninterruptible power supply comprising: an inverter configured to provide power to a load; a communication interface configured to provide a measured value of inverter output current of the uninterruptible power supply to the second uninterruptible power supply, and to receive a measured value of inverter output current of the second uninterruptible power supply; and a controller coupled to the inverter and the communication interface and configured to control the uninterruptible power supply to operate in one of a master state and a slave state, wherein in the master state the uninterruptible power supply is configured to control voltage to the load, and in the slave state the uninterruptible power supply is configured to determine a reference output current value based the measured value of inverter output current of the second uninterruptible power supply and to drive inverter output current of the uninterruptible power supply toward the reference output current value.