System and method for limiting losses in an uninterruptible power supply

• US 8,450,876 B2
• Filed: 07/02/2012
• Issued: 05/28/2013
• Est. Priority Date: 01/27/2009
• Status: Active Grant

• Current Assignee: Schneider Electric IT Corporation (Schneider Electric SE)
• Original Assignee: Schneider Electric IT Corporation (Schneider Electric SE)
• Inventors: Rodenhiser, Fred William, Deokar, Vishwas Mohaniraj, Paik, Namwook, Sheng-Hsien, Fang
• Primary Examiner(s): Amrany, Adi
• Application Number:
  US13/539,924
• Publication Number:
  US 20130002029A1
• Time in Patent Office: 330 Days
• Field of Search: 307 64- 66
• US Class Current: 307/64
• CPC Class Codes: H02J 9/00 Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
• CPC Class Codes: H02J 9/062 for AC powered loads

Abstract

Aspects of the invention are directed to systems and method for limiting losses in an uninterruptible power supply. In one aspect, the present invention provides an uninterruptible power supply (UPS) comprising an input to receive input power having an input voltage, an output to provide output power having an output voltage, a neutral line, an automatic voltage regulation (AVR) transformer coupled to the input and the output of the UPS and having an input, an output, a core and at least one switch controllably coupled to at least one of the core, the input and the output, and a means for isolating the core of the AVR transformer from the neutral line when the input voltage is substantially equal to a defined output voltage.

Claims

1. An uninterruptible power supply (UPS) system comprising:

an input to receive input power having an input voltage with an AC voltage waveform;

an output to provide output power;

a neutral line;

an automatic voltage regulation (AVR) transformer having an input coupled to the input of the UPS system, an output coupled to the output of the UPS system, and a core;

a bypass switch configured to selectively couple the core of the AVR transformer to the neutral line; and

a controller configured to determine whether the input voltage is in a normal or abnormal condition and in response to a determination that the input voltage is in a normal condition, to control the bypass switch to decouple the core from the neutral line.

2. The UPS system of claim 1, wherein the controller is further configured to, in response to a determination that the input voltage is in an abnormal condition, control the bypass switch to couple the core to the neutral line.

3. The UPS system of claim 2, wherein the controller is further configured to control the bypass switch to decouple the core from the neutral line at a zero crossing of the AC voltage waveform and to couple the core to the neutral line at a zero crossing of the AC voltage waveform.

4. The UPS system of claim 1, further comprising a DC voltage source and an inverter coupled to the DC voltage source, wherein the inverter is coupled to the input of the AVR transformer and is configured to provide regulated AC power to the AVR transformer.

5. The UPS system of claim 4, further comprising a transfer relay configured to selectively couple the input of the AVR transformer to one of the inverter and the input of the UPS system.

6. The UPS system of claim 5, wherein the controller is further configured to, in response to a determination that the input voltage is in a second abnormal condition, control the transfer relay to couple the inverter to the input of the AVR transformer and to control the bypass switch to decouple the core from the neutral line.

7. The UPS system of claim 4, wherein the DC voltage source includes a battery.

8. The UPS system of claim 1, wherein the bypass switch is an electromagnetic switch.

9. A method of providing stable power in an uninterruptible power supply (UPS) including an automatic voltage regulation (AVR) transformer, an input to receive input power having an input voltage with an AC voltage waveform, an output to provide output power having an output voltage, and a neutral line, the AVR transformer having an input, an output and a core selectively coupled to the neutral line, the method comprising:

determining whether the input voltage to the UPS is in a normal condition;

determining whether the input voltage to the UPS is in an abnormal condition; and

in response to a determination that the input voltage to the UPS is in a normal condition, decoupling the core of the AVR transformer from the neutral line.

10. The method of claim 9, further comprising in response to a determination that the input voltage to the UPS is in a normal condition, configuring the AVR transformer to provide output power to the output of the UPS with an output voltage equal to the input voltage at the input of the UPS.

11. The method of claim 10, wherein decoupling the core of the AVR transformer from the neutral line includes decoupling the core of the AVR transformer from the neutral line at least one half cycle after a determination that the input voltage to the UPS is in a normal condition.

12. The method of claim 9, wherein determining whether the input voltage to the UPS is in an abnormal condition includes determining whether the input voltage to the UPS is in a blackout, sag or swell condition.

13. The method of claim 12, wherein the UPS further includes a DC voltage source and an inverter, the inverter coupled to the DC voltage source and selectively coupled to the input of the AVR transformer, wherein the method further comprises:

in response to a determination that the input voltage to the UPS is in a blackout condition, coupling the inverter to the input of the AVR transformer and decoupling the core of the AVR transformer from the neutral line; and

providing regulated AC power from the inverter to the input of the AVR transformer.

14. The method of claim 12, further comprising in response to a determination that the input voltage to the UPS is in a sag condition, coupling the core of the AVR transformer to the neutral line and configuring the AVR transformer to provide output power to the output of the UPS with an output voltage greater than the input voltage at the input of the UPS.

15. The method of claim 14, wherein configuring the AVR transformer to provide output power to the output of the UPS with an output voltage greater than the input voltage includes coupling the input and the output of the AVR transformer to the core in a first configuration at least one half cycle after the core of the AVR transformer is coupled to the neutral line.

16. The method of claim 15, further comprising in response to a determination that the input voltage to the UPS is in a swell condition, coupling the core of the AVR transformer to the neutral line and configuring the AVR transformer to provide output power to the output of the UPS with an output voltage less than the input voltage at the input of the UPS.

17. The method of claim 16, wherein configuring the AVR transformer to provide output power to the output of the UPS with an output voltage less than the input voltage includes coupling the input and the output of the AVR transformer to the core in a second configuration at least one half cycle after the core of the AVR transformer is coupled to the neutral line.

18. The method of claim 9, wherein decoupling the core of the AVR transformer from the neutral line includes decoupling the core of the AVR transformer from the neutral line at a zero crossing of the AC voltage waveform.

19. An uninterruptible power supply (UPS) system comprising:

an input to receive input power having an input voltage with an AC voltage waveform;

an output to provide output power;

a neutral line;

an automatic voltage regulation (AVR) transformer having an input coupled to the input of the UPS system, an output coupled to the output of the UPS system, and a core; and

means for preventing energy losses in the AVR transformer when the input voltage is in a normal condition.

20. The UPS system of claim 19, further comprising means for maintaining output power at the output of the UPS within a predetermined threshold while the input voltage is in an abnormal condition.