Apparatus and method for operating an uninterruptible power supply

• US 8,228,046 B2
• Filed: 06/16/2009
• Issued: 07/24/2012
• Est. Priority Date: 06/16/2009
• Status: Active Grant

• Current Assignee: American Power Conversion Corporation (Schneider Electric SE)
• Original Assignee: American Power Conversion Corporation (Schneider Electric SE)
• Inventors: Ingemi, Michael J., Klikic, Damir
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): Mehari, Yemane
• Application Number:
  US12/485,285
• Publication Number:
  US 20100315849A1
• Time in Patent Office: 1,134 Days
• Field of Search: 323222-225, 323282-283, 363/21.05, 363/86, 363/123, 307 64- 66
• US Class Current: 323/222
• CPC Class Codes: H02J 9/062 for AC powered loads
• CPC Class Codes: H02J 9/063 Common neutral, e.g. AC input neutral line connected to AC output neutral line and DC middle point
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• CPC Class Codes: H02M 1/10 Arrangements incorporating converting means for enabling loads to be operated at will from different kinds of power supplies, e.g. from ac or dc
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

Systems and methods for operating an uninterruptable power supply are provided. The uninterruptable power supply may include a rectifier that has a transistor and an inductor. The uninterruptable power supply may also include a controller. A current sensor can be configured to detect inductor current and to provide a detected inductor current value to the controller to generate a current error value based and to generate a pulse width modulation control signal based in part on the current error value. The controller can apply the pulse width modulation control signal to the transistor to adjust a switching frequency of the transistor.

Claims

1. An uninterruptable power supply, comprising:

an input circuit including a first transistor and a first inductor, the input circuit being configured to receive an AC voltage at an input and provide a DC voltage at an output;

a controller having a digital signal processor and a field programmable gate array, the controller being coupled to the input circuit to detect inductor current and to provide a detected inductor current value to the digital signal processor, the controller being configured to apply a pulse width modulation control signal to the first transistor to adjust a switching frequency of the first transistor to generate the DC voltage at the output; and

wherein the first transistor forms part of a first boost converter circuit;

wherein the second transistor forms part of a second boost converter circuit;

wherein the input circuit includes a three phase rectifier;

wherein the controller is further configured to apply the pulse width modulation control signal to the first transistor to switch a mode of operation of the first boost converter circuit between variable frequency just-discontinuous and fixed frequency continuous modes of operation during a first portion of a line cycle; and

the controller is further configured to apply a second pulse width modulation control signal to the second transistor to switch a mode of operation of the second boost converter circuit between variable frequency just-discontinuous and fixed frequency continuous modes of operation during a second portion of the line cycle.

2. The uninterruptable power supply of claim 1, wherein:

the digital signal processor is configured to generate a current error value based in part on the detected inductor current value and to provide the current error value to the field programmable gate array; and

the field programmable gate array is configured to generate the pulse width modulation control signal based in part on the current error value.

3. The uninterruptable power supply of claim 1, wherein in one mode the first boost converter circuit operates in the variable frequency just-discontinuous mode of operation, and the second boost converter circuit simultaneously operates in the fixed frequency continuous mode of operation.

4. The uninterruptable power supply of claim 1, the controller is further configured to apply the pulse width modulation control signal to one of the first transistor and the second transistor to reversibly switch the mode of operation of one of the first boost converter circuit and the second boost converter circuit between variable frequency just-continuous and fixed frequency continuous modes of operation based on a detected phase angle of the line cycle.

5. The uninterruptable power supply of claim 4, wherein at least one of the first transistor and the second transistor switches to an on state when the detected inductor current value falls to substantially zero.

6. The uninterruptable power supply of claim 4, wherein:

the three phase rectifier is configured for operation during a line cycle having a first phase voltage, a second phase voltage, and a third phase voltage; and

the controller is further configured to switch the operating mode of one of the first boost converter circuit and the second boost converter circuit during a part of the line cycle where each of the first phase voltage, the second phase voltage, and the third phase voltage are mutually exclusive.

7. The uninterruptable power supply of claim 1, wherein:

the digital signal processor is further configured to generate a voltage error value based on a value of the DC voltage at the output and to provide the voltage error value to the field programmable gate array; and

the field programmable gate array is further configured to generate the pulse width modulation control signal based in part on the voltage error value.

8. The uninterruptable power supply of claim 1, wherein:

the input circuit includes a three phase rectifier; and

the switching frequency of the first transistor remains between 20 kHz and 130 kHz during a line cycle of the three phase rectifier.

9. The uninterruptable power supply of claim 1, wherein:

the input circuit includes a three phase rectifier having the first inductor, a second inductor, and a third inductor; and

the detected inductor current includes current from at least two of the first inductor, the second inductor, and the third inductor.

10. The uninterruptable power supply of claim 1, wherein the first transistor is in an off state for at least a predetermined amount of time before switching to an on state.

11. The uninterruptable power supply of claim 1, wherein the first transistor is in an on state for at least a predetermined amount of time before switching to an off state.

12. The uninterruptable power supply of claim 1, wherein one of the first transistor and the second transistor reversibly switches between a plurality of on states and off states, and wherein a time period between a first on state and a subsequent on state is approximately 12.5 μ

s.

13. A method of operating an uninterruptable power supply including an input circuit, the input circuit having a first transistor and a first inductor, a controller having a digital signal processor and a field programmable gate array, and a second transistor, wherein the first transistor forms part of a first boost converter circuit and wherein the second transistor forms part of a second boost converter circuit, the method comprising:

detecting inductor current of the input circuit;

providing a detected inductor current value to the digital signal processor;

generating a current error value based in part on the detected inductor current value;

providing the current error value to the field programmable gate array;

generating a pulse width modulation control signal based in part on the current error value;

applying the pulse width modulation control signal to the first transistor to control a switching frequency of one of the first transistor and the second transistor;

applying the pulse width modulation control signal to the first transistor to switch a mode of operation of the first boost converter circuit between variable frequency just-continuous and fixed frequency continuous modes of operation during a first portion of a line cycle; and

applying a second pulse width modulation control signal to the second transistor to switch a mode of operation of the second boost converter circuit between variable frequency just-continuous and fixed frequency continuous modes of operation during a second portion of the line cycle.

14. The method of claim 13, further comprising:

reversibly switching the mode of operation of one of the first boost converter and the second boost converter between variable frequency just-continuous and fixed frequency continuous modes of operation based on a detected phase angle of the line cycle.

15. The method of claim 13, further comprising:

generating a voltage error value of the input circuit;

providing the voltage error value to the field programmable gate array; and

generating the pulse width modulation control signal based in part on the voltage error value.

16. The method of claim 13, wherein the input circuit includes a three phase rectifier having a plurality of inductors including the first inductor, and wherein detecting inductor current of the input circuit further comprises:

detecting inductor current from at least two of the plurality of inductors.

17. An uninterruptable power supply, comprising:

an input circuit including a first transistor, a second transistor, and an inductor, the first transistor forming part of a first boost converter circuit, the second transistor forming part of a second boost converter circuit;

a controller having a digital signal processor and a field programmable gate array and coupled to the input circuit to detect inductor current and to provide a detected inductor current value to the digital signal processor; and

means for applying a pulse width modulation control signal to one of the first transistor and the second transistor to adjust a switching frequency of one of the first transistor and the second transistor to switch a mode of operation of the first boost converter circuit between variable frequency just-discontinuous and fixed frequency continuous modes of operation during a first portion of a line cycle and to switch a mode of operation of the second boost converter circuit between variable frequency just-discontinuous and fixed frequency continuous modes of operation during a second portion of a line cycle.

18. The uninterruptable power supply of claim 17, wherein the means for applying the pulse width modulation control signal further comprises means for:

generating a current error value based in part on the detected inductor current value and to provide the current error value to the field programmable gate array;

limiting the switching frequency between an upper frequency and a lower frequency; and

generating the pulse width modulation control signal based in part on the current error value.