Adjustable battery charger for UPS

• US 7,944,182 B2
• Filed: 08/03/2007
• Issued: 05/17/2011
• Est. Priority Date: 08/03/2007
• Status: Active Grant

• Current Assignee: American Power Conversion Corporation (Schneider Electric SE)
• Original Assignee: American Power Conversion Corporation (Schneider Electric SE)
• Inventors: Beg, Mirza Akmal, Masciarelli, Francis, Petrovic, Luka
• Primary Examiner(s): Muralidar; Richard V
• Application Number:
  US11/833,600
• Publication Number:
  US 20090033283A1
• Time in Patent Office: 1,383 Days
• Field of Search: 320/157, 320/158, 320162-164, 307/64, 307/66, 702/64
• US Class Current: 320/162
• CPC Class Codes: H02J 9/062 for AC powered loads

Abstract

An uninterruptible power supply (UPS) having an adjustable battery charger that generates a charger current, and a controller, coupled to the adjustable battery charger, that receives a signal representative of a system constraint and provides a reference, based on the signal, to the adjustable battery charger to control an amplitude of the charger current supplied by the adjustable battery charger based on the system constraint. The system constraint may include, for example, a maximum input current to the UPS, maximum charging current of the battery cell, and maximum and/or minimum charger current values.

Claims

1. A method of optimizing battery charger power in an uninterruptible power supply (UPS), the method comprising:

generating a charger current;

supplying the charger current to a battery array coupled to the UPS;

monitoring an input current to the UPS by comparing the amplitude of the input current with a signal representative of a first predetermined limit;

if the amplitude of the input current exceeds the first predetermined limit, reducing the charger current; and

if the amplitude of the input current is less than a second predetermined limit, increasing the charger current;

wherein increasing the charger current includes;

increasing the charger current by a predetermined increment; and

repeating the acts of comparing the amplitude of the input current with the signal representative of the first predetermined limit and increasing the charger current by the predetermined increment until the amplitude of the input current reaches the first predetermined limit.

2. The method as claimed in claim 1, further comprising:

comparing an amplitude of the increased charger current with a predetermined maximum charger current value; and

if the amplitude of the charger current is greater than the predetermined maximum charger current value, decreasing the charger current to the predetermined maximum charger current value.

3. A method of optimizing battery charger power in an uninterruptible power supply (UPS), the method comprising:

generating a charger current;

supplying the charger current to a battery array coupled to the UPS;

monitoring an input current to the UPS by comparing the amplitude of the input current with a signal representative of a first predetermined limit; and

if the amplitude of the input current exceeds the first predetermined limit, reducing the charger current;

wherein decreasing the charger current includes;

decreasing the charger current by a predetermined increment; and

repeating the acts of comparing the amplitude of the input current with the signal representative of the first predetermined limit and decreasing the charger current by the predetermined increment, until the amplitude of the input current falls below the first predetermined limit.

4. The method as claimed in claim 3, further comprising:

comparing an amplitude of the reduced charger current with a predetermined minimum charger current value; and

if the amplitude of the reduced charger current is below the predetermined minimum charger current value, increasing the charger current to the predetermined minimum charger current value.

5. An uninterruptible power supply comprising:

an input module configured to receive input power;

at least one battery;

an output module configured to provide output power derived from at least one of the input power and battery power;

an adjustable battery charger, coupled to the at least one battery, that generates a charger current; and

a controller, coupled to the adjustable battery charger, that receives a signal representative of a system constraint and provides a reference, based on the signal, to the charger to control amplitude of the charger current based on the system constraint;

wherein the system constraint includes a maximum input current to the uninterruptible power supply; and

wherein the controller is configured to monitor input current to the uninterruptible power supply and to adjust the reference to decrease the charger current responsive to the input current exceeding the maximum input current.

6. The uninterruptible power supply as claimed in claim 5, further comprising a comparator, coupled to the controller, that receives the signal and the input current to the uninterruptible power supply, compares an amplitude of the input current with a maximum amplitude specified by the signal, and produces an error signal based on the comparison.

7. The uninterruptible power supply as claimed in claim 6, wherein the controller is configured to adjust the reference based on the error signal.

8. The uninterruptible power supply as claimed in claim 7, wherein the controller is further configured to decrease the reference by a predetermined increment responsive to the error signal indicating that the input current exceeds the maximum input current, to monitor the error signal, and to incrementally decrease the reference by the predetermined increment until the amplitude of the input current falls below the maximum input current.

9. The uninterruptible power supply as claimed in claim 5, further comprising a current limiter coupled to the controller, wherein the current limiter is configured to receive the reference and to adjust the reference to limit the charger current to within a predetermined range of amplitudes.

10. The uninterruptible power supply as claimed in claim 5, wherein the system constraint further includes a maximum charger current value.

11. The uninterruptible power supply as claimed in claim 10, wherein the controller is configured to compare an amplitude of the charger current to the maximum charger current value and to dynamically adjust the reference to maintain the charger current amplitude substantially at the maximum charger current value without allowing the input current to exceed the maximum input current.