System and method for exchangeable capacitor modules for high power inverters and converters

• US 8,982,591 B2
• Filed: 03/01/2012
• Issued: 03/17/2015
• Est. Priority Date: 10/18/2011
• Status: Active Grant

• Current Assignee: Tigo Energy, Inc
• Original Assignee: Tigo Energy, Inc
• Inventors: Avrutsky, Mordechay
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): Mehari, Yemane
• Application Number:
  US13/410,175
• Publication Number:
  US 20130094262A1
• Time in Patent Office: 1,111 Days
• Field of Search: 363/35, 363/37, 363/95, 363/97, 363/98, 363123-125, 363/131, 363/132
• US Class Current: 363/95
• CPC Class Codes: G01R 31/42 AC power supplies
• CPC Class Codes: G01R 31/64 Testing of capacitors
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 7/04 by static converters
• CPC Class Codes: H02M 7/4807 having a high frequency intermediate AC stage

Abstract

A method of and system for monitoring condition of a large capacitor connected across an output of a rectifier circuit in an operating electrical power transmission circuit in order to anticipate capacitor failure and facilitate appropriate corrective action is disclosed. The method includes measuring a ripple voltage on the capacitor and ripple current through the capacitor, determining from a representative signal whether the signal exceeds a predetermined threshold; and sending an output to a controller on a system operator if the signal exceeds the predetermined threshold. The ripple current and ripple voltage measurements may be provided as inputs to a digital to analog converter which produces and sends the representative signal to a microprocessor to generate the output to the controller.

Claims

1. A method comprising:

providing a capacitor having a cutout switch to selectively remove the capacitor from electrical connection to a circuitry of a power inverter;

measuring a ripple voltage on the capacitor;

measuring a ripple current through the capacitor;

determining a representative signal from the ripple voltage and current measurements;

determining whether the signal exceeds a predetermined threshold; and

sending an output to a controller if the signal exceeds the predetermined threshold.

2. The method according to claim 1 wherein the ripple current and ripple voltage measurements are provided as inputs to a digital to analog converter and wherein the converter produces and sends the representative signal to a microprocessor to generate the output to the controller.

3. The method according to claim 1 wherein the measuring of ripple current is performed by a rectifier and amplifier module to produce a direct current representative signal.

4. The method according to claim 1 wherein the measuring of ripple voltage is performed by a voltage divider module.

5. The method according to claim 2 further comprising sensing a temperature of the capacitor and sending a temperature signal to the digital to analog converter.

6. The method according to claim 2 further comprising recommending to a master module replacing the capacitor when the controller receives an output from the microprocessor.

7. A power inverter comprising:

a box housing an electrical circuit therein including a dc to ac converter;

at least one electrolytic capacitor mounted to an exterior of the box, the capacitor being connected with the electrical circuit within the box, the capacitor including a cutout switch for selectively removing the capacitor from electrical connection to the circuitry within the box; and

a capacitor health monitoring circuit operably connected to the capacitor to measure a ripple voltage on the capacitor, and

measure a ripple current through the capacitor.

8. The inverter according to claim 7 wherein the monitoring circuit includes a microprocessor programmed to perform operations of:

determining a representative signal from the ripple voltage and current measurements;

determining whether the signal exceeds a predetermined threshold; and

sending an output to a controller if the signal exceeds the predetermined threshold.

9. The inverter according to claim 7 wherein the ripple current and ripple voltage are analyzed in a microprocessor programmed to compare a signal representative of the ripple current and ripple voltage to a predetermined threshold.

10. The inverter according to claim 9 wherein the monitoring circuit issues an output signal when the ripple current and ripple voltage exceed the predetermined threshold.

11. The inverter according to claim 7 wherein the health monitoring circuit has a current sensor in series with the capacitor.

12. The inverter according to claim 7 wherein the health monitoring circuit is connected in parallel with the capacitor.

13. The inverter according to claim 7 wherein the health monitoring circuit includes a temperature sensor operable to sense ambient temperature around the capacitor.

14. A health monitoring system, the system comprising:

a capacitor having a cutout switch to selectively remove the capacitor from electrical connection to a circuitry of a power inverter;

a ripple voltage detector connected across the capacitor;

a ripple current detector connected in series with the capacitor;

a measuring module connected to the voltage and current detectors operable to produce a signal representative of the ripple voltage and current and send an output to a controller if the signal exceeds a predetermined threshold.

15. The system according to claim 14 wherein the measuring module includes an analog-to-digital converter connected to a microprocessor which generates the output to the controller.

16. The system according to claim 14 wherein the ripple voltage detector is a voltage divider module.

17. The system according to claim 16 wherein the ripple current detector is a rectifier and amplifier module.

18. The system according to claim 17 wherein outputs of the voltage divider module and rectifier and amplifier module are fed to an analog-to-digital converter.