Three-phase uninterruptible power system and operation method

An operation method of a three-phase uninterruptible power system, the three-phase uninterruptible power system comprising a DC bus and three power conversion circuits, each power conversion circuit being electrically coupled to the DC bus, a battery pack and one phase of a three-phase power, and each power conversion circuit being configured to perform an AC-DC conversion and a DC-DC conversion, the operation method comprising the steps of:

• determining whether the three-phase uninterruptible power system enters a line mode from a battery mode;
• and
• when the determination is positive, performing a huge current suppression for each power conversion circuit according to a predetermined sequence, the huge current suppression performed for any of the power conversion circuits comprising the steps of:
• disabling the DC-DC conversion of the power conversion circuit, and having the other two power conversion circuits to additionally share the original load of the disabled power conversion circuit;
• and
• after the DC-DC conversion of the power conversion circuit is disabled, enabling the AC-DC conversion of the power conversion circuit, and having the power conversion circuits revert to their original load.