Uninterruptible power supply system and uninterruptible power supply

Patent metadata

Field	Value
Publication number	US-10790698-B2
Application number	US-201916260728-A
Country	US
Kind code	B2
Filing date	Jan 29, 2019
Priority date	Feb 21, 2017
Publication date	Sep 29, 2020
Grant date	Sep 29, 2020

Abstract

A plurality of uninterruptible power supplies of an uninterruptible power supply system controls start or stop of shared current supply from power converters to a load based on shared current commands, which indicate command values for determining a value of shared current to be supplied from the power converters of the plurality of uninterruptible power supplies to the load.

First claim

What is claimed is:

1. An uninterruptible power supply system, comprising:
a plurality of uninterruptible power supplies connected in parallel to each other to a load, wherein
each of the plurality of uninterruptible power supplies includes a power converter that supplies current to the load and a controller, and
the controller included in each of the plurality of uninterruptible power supplies controls start or stop of shared current supply from the power converter based on a shared current command in the power converter of its uninterruptible power supply, generated based on current shunted to the power converter of its uninterruptible power supply and the power converter of another uninterruptible power supply that are performing parallel operation.

2. The uninterruptible power supply system according to claim 1 , wherein the controller performs control of comparing a shared current level according to a magnitude of the shared current command with a first start threshold common to the plurality of uninterruptible power supplies, integrating a time in which the shared current level becomes equal to or higher than the first start threshold, and starting the shared current supply from the power converter when an integrated value becomes equal to or higher than a second start threshold provided for each power converter to determine whether or not the shared current supply is started from the power converter.

3. The uninterruptible power supply system according to claim 2 , wherein the controller performs control of comparing the shared current level according to the magnitude of the shared current command with the first start threshold common to the plurality of uninterruptible power supplies and subtracting a time in which the shared current level becomes lower than the first start threshold from the integrated value when the shared current level becomes lower than the first start threshold after the shared current level becomes equal to or higher than the first start threshold.

4. The uninterruptible power supply system according to claim 2 , wherein the second start threshold decreases as the shared current level increases.

5. The uninterruptible power supply system according to claim 2 , wherein the first start threshold increases as a number of power converters that supply shared current to the load increases.

6. The uninterruptible power supply system according to claim 2 , wherein
the plurality of uninterruptible power supplies includes at least three uninterruptible power supplies,
power converters provided in the at least three uninterruptible power supplies are assigned to a first power converter that constantly supplies shared current to the load and a plurality of second power converters that starts or stops the shared current supply according to a magnitude of the shared current to the load, and
priorities are set on the plurality of power converters, and smaller second start thresholds are assigned as set priorities are higher.

7. The uninterruptible power supply system according to claim 6 , wherein
the controller provided in each of the plurality of uninterruptible power supplies is connected by a signal line through which the power converters of the plurality of uninterruptible power supplies communicate their supply start states or supply stop states to each other, and
when the integrated value becomes equal to or higher than the second start threshold and the shared current supply from any of the plurality of second power converters is started, a priority of remaining second power converters is raised, and the second start threshold corresponding to a raised priority is assigned.

8. The uninterruptible power supply system according to claim 1 , wherein the controller performs control of comparing the shared current level according to a magnitude of the shared current command with a first stop threshold common to the plurality of uninterruptible power supplies, integrating a time in which the shared current level becomes equal to or lower than the first stop threshold, and stopping the shared current supply from the power converter when an integrated value becomes equal to or higher than a second stop threshold provided for each power converter to determine whether or not the shared current supply is stopped from the power converter.

9. The uninterruptible power supply system according to claim 8 , wherein the second stop threshold decreases as the shared current level decreases.

10. The uninterruptible power supply system according to claim 8 , wherein the first stop threshold decreases as a number of power converters that supply shared current to the load decreases.

11. The uninterruptible power supply system according to claim 8 , wherein
the plurality of uninterruptible power supplies includes at least three uninterruptible power supplies,
power converters provided in the at least three uninterruptible power supplies are assigned to a first power converter that constantly supplies shared current to the load and a plurality of second power converters that starts or stops the shared current supply according to a magnitude of the shared current to the load, and
priorities are set on the plurality of power converters, and larger second stop thresholds are assigned as set priorities are higher.

12. The uninterruptible power supply system according to claim 11 , wherein when the shared current supply from any of the plurality of second power converters is stopped, the controller of an uninterruptible power supply including a remaining second power converter temporarily stops control of determining whether or not the shared current supply is stopped from a second power converter of its uninterruptible power supply, and restarts control of determining whether or not the shared current supply is stopped from the second power converter of its uninterruptible power supply after an operation of stopping the shared current supply from any of the plurality of second power converters is completed.

13. The uninterruptible power supply system according to claim 1 , wherein
the plurality of uninterruptible power supplies includes at least three uninterruptible power supplies,
power converters provided in the at least three uninterruptible power supplies are assigned to a first power converter that constantly supplies shared current to the load and a plurality of second power converters that starts or stops the shared current supply according to a magnitude of the shared current to the load, and
a second power converter that has stopped the shared current supply to the load among the plurality of second power converters waits while a phase of an internal inverter command waveform is synchronized with a phase of a voltage waveform supplied by a second power converter that has started the shared current supply to the load in a stop state in which an inverter voltage is not generated.

14. An uninterruptible power supply comprising:
a power converter that shares and supplies current to a load; and
a controller that controls start or stop of shared current supply from the power converter based on a shared current command in its power converter, generated based on current shunted to its power converter and another power converter that are performing parallel operation.

15. The uninterruptible power supply according to claim 14 , wherein the controller performs control of comparing a shared current level according to a magnitude of the shared current command with a first start threshold common to the power converter and the another power converter, integrating a time in which the shared current level becomes equal

Assignees

• Fuji Electric Co Ltd

Inventors

• Umezawa Kazuyoshi

Classifications

• H02M7/493

  the static converters being arranged for operation in parallel · CPC title

• H02J3/46

  Controlling the sharing of generated power between the generators, sources or networks · CPC title

• H02M7/08

  arranged for operation in parallel · CPC title

• H02J9/062 Primary

  for AC powered loads · CPC title

• H02M7/77

  arranged for operation in parallel · CPC title