Parametric multi-cycle averaging in an intelligent electronic device
View Patent ↗A method and apparatus measures electrical power usage and quality, while mitigating the effects of noise on measured signals or parameters. Specifically, a digital electrical power and energy meter employs a method in which a processor averages a parameter, such as voltage or current, over a plurality of cycles of a time-varying signal, such as an AC electrical signal. The method employed by the meter samples a parameter over the plurality of cycles and computes the average of the samples corresponding to the same phase angle of the signal to produce an average signal.
1. A method of displaying a parameter of an alternating current (AC) electrical service on a metering device, wherein the parameter has a noise component, the method comprising:
sensing a parameter of an alternating current (AC) electrical service using a metering module of metering device,
accumulating a predetermined number of consecutives values of the parameter;
calculating an average value of the parameter from the predetermined number of consecutives values;
calculating a weighted average value of the parameter based on the calculated average value and a next consecutive value of the parameter;
determining an absolute value of a difference between the weighted average value and the next consecutive value of the parameter; and
if the absolute value is less than a predetermined threshold, displaying the weighted average value of the parameter.
2. The method of claim 1 , wherein if the absolute value is greater than the predetermined threshold, displaying the next consecutive value of the parameter.
3. The method of claim 2 , wherein the predetermined number of consecutives values of the parameter is adjustable.
4. The method of claim 3 , wherein the greater the predetermined number of consecutives values of the parameter, the steadier the displayed value of the parameter.
5. The method according to claim 2 , wherein the parameter is selected from the group consisting of: a value or a root mean square value of any one of: a line voltage, a line current, a phase voltage, and a phase current; a total harmonic distortion; energy; revenue; real power; reactive power; total power; and a power factor.
6. The method of claim 5 , wherein the predetermined number of consecutives values of the parameter is different for each particular parameter.
7. The method of claim 5 , wherein the predetermined threshold is different for each particular parameter.
8. The method of claim 2 , wherein the predetermined threshold is adjustable.
9. The method of claim 2 , wherein the predetermined threshold is approximately equal to an amplitude of the noise component.
10. The method of claim 2 , wherein the weighted average value is determined using the equation:
F
′
=
F
(
M
-
1
)
+
P
M
+
1
M
wherein F′ is the weighted average value, F is the calculated average, M is the predetermined number of consecutives values and P M+1 is the next consecutive value of the parameter.
11. An intelligent electronic device comprising:
a metering module that obtains values of a parameter of an alternating current (AC) electrical service an AC signal delivered by the AC electrical service;
a processing module that processes the values obtained by the metering module; and
a display module that displays the values of the parameter,
wherein the processing module is operative to accumulate a predetermined number of consecutives values of the parameter, calculate an average value of the parameter from the predetermined number of consecutives values, calculate a weighted average value of the parameter based on the calculated average value and a next consecutive value of the parameter, determine an absolute value of a difference between the weighted average value and the next consecutive value of the parameter, and if the absolute value is less than a predetermined threshold, display the weighted average value of the parameter on the display module.
12. The intelligent electronic device of claim 11 , wherein if the absolute value is greater than the predetermined threshold, the display module displays the next consecutive value of the parameter.
13. The intelligent electronic device of claim 12 , further comprising a user interface module configured for adjusting the predetermined number of consecutives values.
14. The intelligent electronic device of claim 13 , wherein the greater the predetermined number of consecutives values of the parameter, the steadier the displayed value of the parameter.
15. The intelligent electronic device of claim 12 , wherein the parameter is selected from the group consisting of: a value or a root mean square value of any one of: a line voltage, a line current, a phase voltage, and a phase current; a total harmonic distortion; energy; revenue; real power; reactive power; total power; and a power factor.
16. The intelligent electronic device of claim 15 , wherein the predetermined number of consecutives values of the parameter is different for each particular parameter.
17. The intelligent electronic device of claim 15 , wherein the predetermined threshold is different for each particular parameter.
18. The intelligent electronic device of claim 12 , further comprising a user interface module configured for adjusting the predetermined threshold.
19. The intelligent electronic device of claim 12 , wherein the predetermined threshold is approximately equal to an amplitude of the noise component.
20. The intelligent electronic device of claim 12 , wherein the weighted average value is determined using the equation:
F
′
=
F
(
M
-
1
)
+
P
M
+
1
M
wherein F′ is the weighted average value, F is the calculated average, M is the predetermined number of consecutives values and P M+1 is the next consecutive value of the parameter.