MAXIMIZED BATTERY RUN-TIME IN A PARALLEL UPS SYSTEM

• US 20100082173A1
• Filed: 12/03/2009
• Published: 04/01/2010
• Est. Priority Date: 07/06/2005
• Status: Active Grant

• Current Assignee: Vertiv Corporation (Vertiv Holdings Co.)
• Original Assignee: Liebert Corporation (Vertiv Holdings Co.)
• Inventors: Eschhofen, Kevin, Marwali, Mohammad Nanda, Heber, Brian P., Bush, Terry D.
• Granted Patent: US 8,271,146 B2
• Time in Patent Office: Days
• US Class Current: 700/292
• CPC Class Codes: H02J 3/007 Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources for providing uninterruptable power supply H02J9/00
• CPC Class Codes: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02M 7/493 the static converters being arranged for operation in parallel

Abstract

An uninterruptible power supply (UPS) includes a plurality of UPS modules. Each of the UPS modules has a battery that provides power to a protected load in the event of a utility power failure. A plurality of controllers control how much power each of the batteries deliver to the protected load, and a communication bus allows the controllers to exchange information about the battery voltages. One of the controllers calculates the average battery voltage of the plurality of batteries and adjusts the amount of energy provided by an individual battery such that the battery voltage is about equal to the average battery voltage.

Claims

1. A method of controlling battery voltages in each of a plurality of uninterruptible power supply (UPS) modules, comprising:

reducing the energy delivered from at least one battery to a protected load to about zero;

determining whether an inverter delivering power to the protected load is overloaded; and

increasing the energy delivered from the at least one battery until the inverter is not overloaded.

2. The method of claim 1, further comprising:

determining an overload runtime of the inverter;

determining the battery runtime of the at least one battery;

if the battery runtime of the at least one battery is less than the overload runtime of the inverter, reducing the energy of the battery such that the inverter is overloaded.

3. The method of claim 1, further comprising the step of balancing the battery runtime against the overload runtime of the inverter intentionally placed in the overload condition.

4. The method of claim 1, wherein the battery is associated with a UPS module that has lost utility power.

5. The method of claim 4, wherein the reducing step is triggered by the UPS module losing utility power.

6. A method of controlling an uninterruptible power supply comprising:

determining an overload runtime of an inverter;

determining a battery runtime of at least one battery delivering power to a protected load;

if the battery runtime of the at least one battery is less than the overload runtime of the inverter, reducing the energy of the battery such that the inverter is overloaded.

7. The method of claim 6, further including the step of balancing the battery runtime against the overload runtime of the inverter intentionally placed in the overload condition.

8. The method of claim 6, wherein the at least one battery is associated with a UPS module that has lost utility power.

9. The method of claim 8, wherein the determining steps are triggered by the UPS module losing utility power.

10. An uninterruptible power supply (UPS) system, comprising:

a plurality of UPS modules, each UPS module including a battery that provides power to a protected load in the event of a utility power failure;

a plurality of controllers that control how much power each of the batteries deliver to the protected load;

a communication bus that allows the controllers to exchange information about the battery voltages;

wherein at least one of the controllers reduces the amount of power provided by at least one of the batteries to about zero and, if an overload condition is indicated on the communication bus, increases the power provided by the at least one of the batteries until the overload condition is corrected.

11. The system of claim 10, wherein the at least one controller further—

determines an overload runtime of the inverter;

determines the battery runtime of the at least one battery;

if the battery runtime of the at least one battery is less than the overload runtime of the inverter, reduces the energy of the battery such that the inverter is overloaded.

12. The system of claim 10, wherein the at least one controller further balances the battery runtime against the overload runtime of the inverter intentionally placed in the overload condition.

13. The system of claim 10, wherein the least one battery is associated with a UPS module that has lost utility power.

14. The system of claim 13, wherein the controller reduces the amount of power provided by the at least one battery in response to the UPS module losing utility power.

16. The system of claim 12, wherein the at least one controller further balances the battery runtime against the overload runtime of the inverter intentionally placed in the overload condition.

17. The system of claim 12, wherein the battery runtime is related to at least one battery associated with a UPS module that has lost utility power.

18. The system of claim 17, wherein the controller compares the estimated battery runtime with the inverter overload runtime in response to the UPS module losing utility power.

15. An uninterruptible power supply (UPS) system, comprising:

a plurality of UPS modules, each UPS module including a battery that provides power to a protected load in the event of a utility power failure;

a plurality of controllers that control how much power each of the batteries deliver to the protected load;

a communication bus that allows the controllers to exchange information about the battery voltages;

wherein at least one of the controllers compares an estimated battery runtime with an inverter overload runtime and if the estimated battery runtime is less than the overload runtime reduces the power provided by the battery to the protected load.