MAXIMIZED BATTERY RUN-TIME IN A PARALLEL UPS SYSTEM

• US 20070007825A1
• Filed: 06/29/2006
• Published: 01/11/2007
• Est. Priority Date: 07/06/2005
• Status: Active Grant

• Current Assignee: Vertiv Corporation (Vertiv Holdings Co.)
• Original Assignee: Liebert Corporation (Vertiv Holdings Co.)
• Inventors: Heber, Brian, Eschhofen, Kevin, Marwali, Mohammad, Bush, Terry
• Granted Patent: US 7,668,624 B2
• Time in Patent Office: Days
• US Class Current: 307/67
• 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 a plurality of battery voltages in a plurality of uninterruptible power supply (UPS) modules, each of the UPS modules having an inverter for providing power to a load, each of the inverters receiving power from a battery, the method comprising:

determining the average voltage of the batteries from at least two of the UPS modules;

comparing the battery voltage for the batteries from the at least two UPS modules to the average battery voltage; and

generating a control signal responsive to the comparison that causes the inverters to adjust the amount of power delivered by the batteries to the load such that the battery voltage of the batteries from each of the at least two UPS modules is about the average battery voltage.

2. The method of claim 1, wherein comparing the battery voltage comprises providing a first signal responsive to the average battery voltage and a second signal responsive to one of the at least two battery voltages to a controller.

3. The method of claim 2, wherein generating a control signal comprises generating an output signal from the controller and passing the signal to the inverter causing the inverter to shift the phase of its output relative to the phase of the power being supplied to the load.

4. The method of claim 3, wherein shifting the phase includes advancing the phase angle of the inverter output with respect to the phase angle of the power being supplied to the load to decrease the battery voltage relative to the average battery voltage.

5. The method of claim 3, wherein shifting the phase includes decreasing the phase angle of the inverter output with respect to the phase angle of the power being supplied to the load to increase the battery voltage relative to the average battery voltage.

6. A method of controlling battery voltages in each of a plurality of uninterruptible power supply 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.

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

determining an overload runtime of an inverter;

determining the 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.

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

a plurality of UPS modules, each of the UPS modules 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 calculates the average battery voltage of the plurality of batteries and adjusts the amount of energy provided by at least one of the batteries such that the battery voltage is about the average battery voltage.

9. The UPS system of claim 8, wherein the controller compares the battery voltage for the at least one battery to the average battery voltage.

10. The UPS system of claim 8, wherein the controller receives a first signal responsive to the average battery voltage and a second signal responsive to the voltage of the at least on battery.

11. The UPS system of claim 8, wherein each of the UPS modules includes an inverter receiving power from a battery to provide power to the protected load, and wherein the controller outputs a signal to the inverter causing the inverter to shift the phase of its output relative to the phase of the power being supplied to the load.

12. 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.

13. 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.