System and Method for Exchangeable Capacitor Modules for High Power Inverters and Converters

• US 20130094262A1
• Filed: 03/01/2012
• Published: 04/18/2013
• Est. Priority Date: 10/18/2011
• Status: Active Grant

• Current Assignee: Tigo Energy, Inc
• Original Assignee: Tigo Energy, Inc
• Inventors: Avrutsky, Mordechay
• Granted Patent: US 8,982,591 B2
• Time in Patent Office: Days
• US Class Current: 363/125
• 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 of monitoring condition of a capacitor connected across an output of a rectifier circuit in an operating electrical power transmission circuit, the method comprising:

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.

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

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.

9. The inverter according to claim 7, wherein the monitoring circuit senses voltage ripple across the capacitor.

10. The inverter according to claim 7 wherein the capacitor health monitoring circuit senses ripple current through the capacitor.

11. The inverter according to claim 10 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.

12. The inverter according to claim 11 wherein the monitoring circuit issues an output signal when the ripple current and ripple voltage exceed the predetermined threshold.

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

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

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

16. A health monitoring system for monitoring a condition of a capacitor in a power inverter circuit, the system comprising:

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.

17. The system according to claim 16 wherein the measuring module includes an analog-to digital-converter connected to a microprocessor which generates the output to the controller.

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

19. The system according to claim 18 wherein the ripple current detector is a rectifier and amplifier module.

20. The system according to claim 19 wherein outputs of the voltage divider module and rectifier and amplifier module are fed to an analog-to-digital converter.