# US 2013/0154378 A1 · Method for controlling a parallel line-interactive uninterruptible power supply system

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- Number: US 2013/0154378 A1
- Document ID: US20130154378A1
- Status: Published application
- Kind: A1
- Application number: 13/326,596
- Filed: 2011-12-15
- Published: 2013-06-20
- Earliest claimed: 2011-12-15
- Inventors: Kai-Tsung YANG; Jui-Hung Chou; Shih-Chien Tang
- Web page: https://patentgrep.com/patent/US20130154378A1

## CPC

- H02J 9/062: {for AC powered loads}
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY

## Abstract

A method for controlling a parallel line-interactive uninterruptible power supply (UPS) system having multiple line-interactive UPSs parallelly connected, in which each line-interactive UPS has a switching element and a power output terminal connected to a load through the switching element, has a step of acquiring a switching status from the switching element when the switching element is switched to determine next switching time of the switching element so that the switching time is adjacent to a zero phase angle point of an input voltage cycle of the mains power. The method further has the switching elements of all line-interactive UPSs switched at the same time for all the line-interactive UPSs to evenly share the load, thereby preventing the line-interactive UPSs from being damaged due to concentrated load current on single line-interactive UPS arising from dramatically different switching time of the switching elements.

## Claims

### Claim 1

A method for controlling a parallel line-interactive uninterruptible power supply (UPS) system having multiple line-interactive UPSs parallelly connected, wherein each line-interactive UPS has a switching element, a power output terminal connected to a load through the switching element, and a controller controlling the switching element to switch on or off and acquiring a switching status from the switching element, wherein the method is executed by the controller and comprises steps of:
switching the switching element;
acquiring the switching status from the switching element and recording a switching time of the switching element associated with the switching status;
determining if the switching element is switched again;
if the switching element is switched again, adjusting the switching time of the switching element associated with the switching status to be located within a preset range of an input voltage cycle; and
communicating with the controllers of other line-interactive UPSs to synchronously operate all the switching elements.

### Claim 2 (depends on 1)

The method as claimed in claim 1, wherein in the step of adjusting the switching time of the switching element, the switching time of the switching element is adjusted in the proximity of a zero phase angle point of the input voltage cycle.