METHOD FOR CONTROLLING A PARALLEL LINE-INTERACTIVE UNINTERRUPTIBLE POWER SUPPLY SYSTEM

摘要

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.