Reduced cost automatic meter reading system and method using locally communicating utility meters

• US 20050024234A1
• Filed: 08/06/2004
• Published: 02/03/2005
• Est. Priority Date: 08/15/1997
• Status: Active Grant

• Current Assignee: Aclara Meters LLC (Hubbell, Inc.)
• Original Assignee: Daniel Arthur Staver, Daniel David Harrison, Daum D. Wolfgang, Ertugrul Berkcan, Glen William Brooksby, Kenneth Brakeley Ii Welles, Ralph Thomas Hoctor
• Inventors: Daum, D. Wolfgang, Berkcan, Ertugrul, Harrison, Daniel David, Hoctor, Ralph Thomas, Welles, Kenneth Brakeley II, Staver, Daniel Arthur, Brooksby, Glen William
• Granted Patent: US 7,548,223 B2
• Time in Patent Office: Days
• US Class Current: 340/870.100
• CPC Class Codes: G01D 4/004 Remote reading of utility meters to a fixed location
• CPC Class Codes: G01R 21/133 by using digital technique
• CPC Class Codes: G01R 22/00 Arrangements for measuring time integral of electric power or current, e.g. electricity meters
• CPC Class Codes: H04Q 2209/30 using a wired architecture
• CPC Class Codes: H04Q 2209/43 using wireless personal area networks [WPAN], e.g. 802.15, 802.15.1, 802.15.4, Bluetooth or ZigBee
• CPC Class Codes: H04Q 2209/60 for transmitting utility meters data, i.e. transmission of data from the reader of the utility meter
• CPC Class Codes: H04Q 2209/823 where the data is sent when the measured values exceed a threshold, e.g. sending an alarm
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom
• CPC Class Codes: Y02B 90/20 Smart grids as enabling technology in buildings sector smart grids supporting the management or operation of end-user stationary applications in general, or like technologies with no associated climate change mitigation effect Y04S20/00
• CPC Class Codes: Y04S 20/30 Smart metering, e.g. specially adapted for remote reading

Abstract

A low cost and easy to assemble communicating utility meter provides selectable measurement, calibration, display, and communications means so as to be re-configurable based on several factors including; harmonic content of the power signal measured, LCD display alternatives, time of use measurements, bandpass filter settings, power quality measurements, PLC communications. alternatives, radio frequency communications alternatives, optical communications alternatives, and hard wire communications alternatives.

Claims

1. An LCD driver having an inverter signal line, at least one bit line, and an LCD driver line, said LCD driver comprising:

at least one exclusive OR gate coupled to said inverter line and coupled to said at least one bit line, wherein said exclusive OR gate is adapted to generate a voltage signal in correspondence with the logical status of said inverter line and said at least one bit line;

a respective voltage level capacitor coupled to said at least one exclusive OR gate, wherein said respective voltage level capacitor has a capacitance value that is proportional to the numerical significance of said at least one bit line coupled to said at least one exclusive OR gate, and wherein said respective voltage level capacitor is adapted to generate a voltage level proportional to the respective capacitance value and the voltage signal generated by said at least one exclusive OR gate; and

a summing amplifier coupled to each respective voltage level capacitor, wherein said summing amplifier is adapted to sum the voltage level across each respective voltage level capacitor so as to generate a plurality of LCD driving voltage levels.

2. The LCD driver as recited in claim 1, wherein said voltage level capacitor is adapted to generate a plurality of LCD driving voltage levels having an average voltage level of zero volts.

3. A method of responding to a reduction in power supply voltage in a communicating utility meter having non-volatile memory, said power supply having three voltage thresholds, said method comprising the steps of:

first removing power from non-critical functions when the power supply voltage is less than said first threshold;

second, saving critical values in non-volatile memory when the power supply voltage is less than said first threshold and less than said second threshold;

third, taking no action when the power supply voltage is greater than said second threshold and less than said third threshold;

fourth, restarting said communicating utility meter when the power supply voltage is greater than said third threshold.

4. The method as recited in claim 3, wherein the value of said third threshold is greater than the value of said second threshold.

5. The method as recited in claim 4, wherein the value of said first threshold is greater than the value of said second threshold.

6. The method as recited in claim 5, where said non-critical functions comprise external communication hardware, LCD display hardware, and external input/output.

7. The method as recited in claim 6, where said critical values comprise computer memory pointers, accumulated kilowatt-hours, utility meter voltage readings, and utility meter current readings.

8. A method of responding to a reduction in power supply voltage in a communicating utility meter having non-volatile memory, said power supply having a voltage threshold, said method comprising the steps of:

removing power from non-critical functions when the power supply voltage is less than said voltage threshold for a time duration of one voltage cycle; and

saving critical functions in non-volatile memory when the power supply voltage has been below said voltage threshold for four voltage cycles.

9. A re-configurable utility meter, having a current signal and having a voltage signal, said utility meter comprising:

a current sensor;

a voltage sensor;

a DSP coupled to said current sensor and coupled to said voltage sensor, said DSP comprising;

a high pass filter, wherein said high pass filter is adapted to eliminate the DC component and noise from the current sensor signal;

a phase corrector coupled to said high pass filter, wherein said phase corrector is adapted to correct phase error in the current sensor signal;

a gain corrector coupled to said phase corrector, wherein said gain corrector is adapted to correct for gain error in the current sensor signal; and

a power measurement block coupled to said DSP and coupled to said power signal, wherein said power measurement block is adapted to be re-configurable so as to compute real power, reactive power, or apparent power.

11. The re-configurable utility meter as recited in claim 9, further comprising a Time of Use (TOU) function, wherein said TOU function may be selected to generate a plurality of signals indicative of energy usage over specified units of time.

12. The re-configurable utility meter as recited in claim 9, further comprising a demand function, wherein said demand function may be selected to generate a plurality of signals indicative of the rate of energy usage over specified units of time.

13. The re-configurable utility meter as recited in claim 9, further comprising an LCD display, wherein said LCD display may be selected to display power usage in two ways including the display of alpha-numeric data and binary enunciation of the rate of energy consumption.

14. The re-configurable utility meter as recited in claim 9, further comprising a calibration function, wherein said calibration function may be selected to generate at least one calibration signal.

24. The re-configurable utility meter as recited in claim 9, wherein said current sensor comprises a differentiating current sensor.

25. The re-configurable utility meter as recited in claim 24, wherein said DSP further comprises an integrator coupled to said high pass filter, wherein said integrator is adapted to integrate the current sensor signal.

10. A re-configurable utility meter, having a voltage signal and having a current signal, said utility meter comprising:

a current sensor;

a voltage sensor;

a DSP coupled to said current sensor and coupled to said voltage sensor, said DSP comprising;

a high pass filter, wherein said high pass filter is adapted to eliminate the DC component and noise from the voltage sensor signal;

a phase corrector coupled to said high pass filter, wherein said phase corrector is adapted to correct phase error in the voltage sensor signal;

a gain corrector coupled to said phase corrector, wherein said gain corrector is adapted to correct for gain error in the voltage sensor signal; and

a power measurement block coupled to said DSP and coupled to said power signal, wherein said power measurement block is adapted to be re-configurable so as to compute real power, reactive power, or apparent power.

15. The re-configurable utility meter as recited in claim 10, further comprising a Time of Use (TOU) function wherein said TOU function may be selected to generate a plurality of signals indicative of energy usage over specified units of time.

16. The re-configurable utility meter as recited in claim 10, further comprising a demand function, wherein said demand function may be selected to generate a plurality of signals indicative of the rate of energy usage over specified units of time.

17. The re-configurable utility meter as recited in claim 10, further comprising an LCD display, wherein said LCD display may be selected to display power usage in two ways including the display of alpha-numeric data and binary enunciation of the rate of energy consumption.

18. The re-configurable utility meter as recited in claim 10, further comprising a calibration function, wherein said calibration function may be selected to generate at least one calibration signal.

19. A re-configurable utility meter, having a current signal and having a voltage signal, said utility meter comprising:

a current sensor;

a voltage sensor;

a DSP coupled to said current sensor and coupled to said voltage sensor, said DSP comprising;

a current high pass filter, wherein said high pass filter is adapted to eliminate the DC component and noise from the current sensor signal;

a current phase corrector coupled to said current high pass filter, wherein said phase corrector is adapted to correct phase error in the current sensor signal;

a current gain corrector coupled to said current phase corrector, wherein said current gain corrector is adapted to correct for gain error in the current sensor signal;

a voltage high pass filter, wherein said voltage high pass filter is adapted to eliminate the DC component and noise from the voltage sensor signal;

a voltage phase corrector coupled to said voltage high pass filter, wherein said voltage phase corrector is adapted to correct phase error in the voltage sensor signal;

a voltage gain corrector coupled to said voltage phase corrector, wherein said voltage gain corrector is adapted to correct for gain error in the voltage sensor signal; and

a power measurement block coupled to said DSP and coupled to said power signal, wherein said power measurement block is adapted to be re-configurable so as to compute real power, reactive power, or apparent power.

20. The re-configurable utility meter as recited in claim 19, further comprising a Time of Use (TOU) function, wherein said TOU function may be selected to generate a plurality of signals indicative of energy usage over specified units of time.

21. The re-configurable utility meter as recited in claim 19, further comprising a demand function, wherein said demand function may be selected to generate a plurality of signals indicative of the rate of energy usage over-specified units of time.

22. The re-configurable utility meter as recited in claim 19, further comprising an LCD display, wherein said LCD display may be selected to display power usage in two ways including the display of alpha-numeric data and binary enunciation of the rate of energy consumption.

23. The re-configurable utility meter as recited in claim 19, further comprising a calibration function, wherein said calibration function may be selected to generate at least one calibration signal.

26. The re-configurable utility meter as recited in claim 19, wherein said current sensor comprises a differentiating current sensor.

27. The re-configurable utility meter as recited in claim 26, wherein said DSP further comprises an current integrator coupled to said current high pass filter, wherein said current integrator is adapted to integrate the current sensor signal.

28. A circuit for filtering a current sensor signal comprising a second order infinite impulse response (IIR) filter, said IIR filter having a z domain response defined by:

$H<br><br>\left(z\right)=\frac{c<br><br>\left(z^2-1\right)}{z^2-2<br><br>k+{\hat{k}}^2},$

wherein c is a normalization constant, and wherein k is approximately equal to 1, and wherein {circumflex over (k)} is approximately equal to k.

29. The circuit as recited in claim 28, wherein said IIR filter comprises:

a first digital summer;

a unity gain amplifier coupled to said first digital summer;

a normalization constant amplifier coupled to said unity gain amplifier;

a negative unity gain amplifier coupled to said first summer and coupled to said normalization constant amplifier;

a first unit delay coupled to said unity gain amplifier;

a second unit delay coupled to said first unit delay and coupled to said negative unity gain amplifier;

a second summer coupled to said first summer;

a third unit delay coupled to said second summer;

a fourth unit delay coupled to said third unit delay;

a 2k gain amplifier coupled to said fourth unit delay and coupled to said third unit delay;

a third summer coupled to said 2k gain amplifier, and coupled to said second summer; and

a {circumflex over (k)}² gain amplifier coupled to said third summer and coupled to said fourth unit delay.

30. A method of selecting IIR filter constants k and {circumflex over (k)} within a circuit for filtering a current sensor signal, said method comprising the steps of:

selecting a first zero at z=1;

selecting a second zero at z=−

1; and

selecting a pair of poles at the roots of equation z²−

2k+{circumflex over (k)}² sufficiently close to said first zero such that said pair of poles and said first zero appear as a single pole at z=1 for frequencies within a selected pass band.

31. The method of selecting IIR filter constants, as recited in claim 30 wherein k is selected based on the equation k=1−

2<sup>−

n</sup>, wherein n is greater than 7.

32. The method of selecting IIR filter constants, as recited in claim 31 wherein {circumflex over (k)}² is selected based on the equation {circumflex over (k)}²=1−

2<sup>−

(n-1)</sup>.

33. A method of calculating calibration constants used to calibrate a utility meter, said method comprising the steps of:

connecting the voltage signal of a precision voltage supply to the utility meter;

connecting the current signal of a precision current supply to the utility meter;

collecting a plurality of un-calibrated voltage samples and un-calibrated current samples generated by said precision voltage supply and said precision current supply;

performing a Fourier Transform of the voltage samples and a Fourier Transform of the current samples, wherein the amplitude and phase of the respective voltage and current signals is generated; and

calculating calibration constants based on the amplitude and phase of the respective voltage and current signals.

34. A utility meter having pre-selectable communication protocols selectable by the use of “

soft-keys”

, comprising;

a CPU; and

a communication hardware module coupled to said CPU and coupled to an external device, wherein said communications hardware module is adapted to be reconfigured via software to communicate using a standard radio frequency protocol, and alternatively to communicate using a standard serial wire-line protocol, and alternatively to communicate using a standard optical protocol, and alternatively to communicate using a power line carrier protocol.

35. The utility meter as recited in claim 34, wherein said communication hardware module is coupled to said external device utilizing a communication link selected from the group including a optical link, a radio frequency link, and a wired communications link.

36. The utility meter as recited in claim 35, wherein said communication hardware module is adapted to select said protocol based on programming options selected via said “

soft-keys.”

37. A set of utility meter hardware having a base, at least one current sensor, and at least one printed wiring board (PWB), for improved assembly of a utility meter, said utility meter hardware comprising:

a sensor shield adapted to house said current sensor;

said base having a locating pin, wherein said pin is adapted to align said sensor shield to said base so as to provide registration to couple said sensor shield to said base;

at least one snap connector respectively coupled to said at least one PWB, wherein said at least one snap connector is adapted to provide a repeatable electrical connection between said at least one PWB and said at least one current sensor; and

wherein said sensor shield and said base and said at least one PWB is adapted to snap together to form a utility meter housing.

38. The set of utility meter hardware as recited in claim 37, wherein said at least one snap connector is adapted to provide symmetry between said at least one PWB and said at least one current sensor.

39. The set of utility meter hardware as recited in claim 38, further comprising at least one bus bar coupled to said base, wherein said at least one bus bar is adapted to provide repeatable electrical connection between said at least one bus bar and said base.

40. The set of utility meter hardware as recited in claim 39, wherein said at least one bus bar is coupled to said at least one PWB, wherein said at least one bus bar is adapted to provide a repeatable electrical connection between said at least one PWB and said at least one bus bar.

41. The set of utility meter hardware as recited in claim 40, wherein said sensor shield is adapted to be coupled to said current sensor by being snapped together.

42. The set of utility meter hardware as recited in claim 41, wherein said display is adapted to be coupled to one of said printed wiring boards by being snapped together, and wherein said display is adapted to be coupled to said housing by being snapped together.