Method and apparatus for measuring AC voltages

• US 8,299,776 B2
• Filed: 03/21/2011
• Issued: 10/30/2012
• Est. Priority Date: 03/26/2008
• Status: Active Grant

• Current Assignee: Enphase Energy Incorporated
• Original Assignee: Enphase Energy Incorporated
• Inventors: Fornage, Martin
• Primary Examiner(s): NGUYEN, HOAI AN D
• Application Number:
  US13/065,382
• Publication Number:
  US 20110169479A1
• Time in Patent Office: 589 Days
• Field of Search: 324/76.11, 324/522, 702/1, 702/57, 702/64, 340/660, 340/662, 340/663
• US Class Current: 324/76.11
• CPC Class Codes: G01R 1/203 Resistors used for electric measuring, e.g. decade resistors standards, resistors for comparators, series resistors, shunts resistors in general H01C; microwave or radiowave terminations H01P1/26; coupling devices H01R
• CPC Class Codes: G01R 15/22 using light-emitting devices, e.g. LED, optocouplers G01R31/31901 takes precedence
• CPC Class Codes: G01R 19/0084 measuring voltage only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• CPC Class Codes: G01R 19/2503 for measuring voltage only, e.g. digital volt meters (DVM's) G01R19/2506 - G01R19/257 take precedence

Abstract

A method and apparatus for measuring an AC voltage. In one embodiment, the apparatus includes an AC voltage monitor, including a solid state electrical isolation device, enabled to (i) generate at least a first voltage measurement of an AC power source, (ii) generate a serial data stream frame based on the at least a first voltage measurement, and (iii) transmit the serial data stream frame via the solid state electrical isolation device.

Claims

1. Apparatus for measuring an AC voltage, comprising:

an AC voltage monitor, comprising a solid state electrical isolation device, enabled to (i) generate a plurality of voltage samples, wherein each voltage sample of the plurality of voltage samples is from a different AC line of a plurality of AC lines;

(ii) generate at least a first voltage measurement based on the plurality of voltage samples;

(iii) generate a serial data stream frame based on the at least a first voltage measurement; and

(iv) transmit the serial data stream frame via the solid state electrical isolation device.

2. The apparatus of claim 1, wherein the AC voltage monitor (i) obtains a first and a second voltage sample from a first and a second AC line, respectively, of the plurality of AC lines and (ii) computes a difference between the first and the second voltage samples to generate the at least a first voltage measurement.

3. The apparatus of claim 2, wherein the AC voltage monitor comprises an analog-to-digital (ADC) bank that samples and digitizes voltages from the first and the second AC lines to generate the first and the second voltage samples, respectively.

4. The apparatus of claim 2, wherein voltages on the first and the second AC lines are at least one of scaled or low pass filtered prior to obtaining the first and the second voltage samples.

5. The apparatus of claim 2, wherein the AC voltage monitor further obtains a third and a fourth voltage sample from a third and a fourth AC line, respectively, of the plurality of AC lines and computes a difference between (iv) the third and the second voltage samples and (v) the fourth and the second voltage samples to generate the at least a first voltage measurement.

6. The apparatus of claim 5, wherein the first, the second, the third, and the fourth AC lines are a first phase, a neutral line, a second phase, and a third phase, respectively.

7. The apparatus of claim 1, wherein the serial data stream frame comprises data representing the at least a first voltage measurement and a frame word.

8. The apparatus of claim 7, wherein the AC voltage monitor comprises a universal asynchronous receiver-transmitter (UART) for generating the serial data stream frame.

9. The apparatus of claim 1, wherein the solid state electrical isolation device is an optocoupler.

10. The apparatus of claim 1, wherein the AC voltage monitor generates a DC voltage from an AC power source, coupled to the plurality of AC lines, for powering at least one component of the AC voltage monitor.

11. A method for measuring an AC voltage, comprising:

generating a plurality of voltage samples, wherein each voltage sample of the plurality of voltage samples is from a different AC line of a plurality of AC lines;

generating at least a first voltage measurement based on the plurality of voltage samples;

generating a serial data stream frame based on the at least a first voltage measurement; and

transmitting the serial data stream frame via a solid state electrical isolation device.

12. The method of claim 11, wherein generating the plurality of voltage samples comprises obtaining a first and a second voltage sample of a first and a second AC line, respectively, of the plurality of AC lines;

and wherein generating the at least a first voltage measurement comprises computing a difference between the first and the second voltage samples.

13. The method of claim 12, wherein obtaining the first and the second voltage samples comprises sampling and digitizing, via an analog-to-digital (ADC) bank, voltages from the first and the second AC lines to generate the first and the second voltage samples, respectively.

14. The method of claim 12, further comprising at least one of scaling or low pass filtering voltages on the first and the second AC lines prior to obtaining the first and the second voltage samples.

15. The method of claim 12, wherein generating the plurality of voltage samples further comprises obtaining a third and a fourth voltage sample from a third and a fourth AC line, respectively, of the plurality of AC lines;

and wherein generating the at least a first voltage measurement further comprises computing a difference between the third and the second voltage samples, and computing a difference between the fourth and the second voltage samples.

16. The method of claim 15, wherein the first, the second, the third, and the fourth AC lines are a first phase, a neutral line, a second phase, and a third phase, respectively.

17. The method of claim 11, further comprising generating a frame word, wherein the serial data stream frame comprises data representing the at least a first voltage measurement and the frame word.

18. The method of claim 11 further comprising generating, by a universal asynchronous receiver-transmitter (UART), the serial data stream frame.

19. The method of claim 11, wherein the solid state electrical isolation device is an optocoupler.

20. The method of claim 11, further comprising generating a DC voltage from an AC power source coupled to the plurality of AC lines;

and powering, by the DC voltage, at least one component of a device that generates the at least a first voltage measurement, generates the serial data stream frame, and transmits the serial data stream frame.