Universal grid analyzer
Embodiments of the present invention may provide a device for monitoring electric power at the distribution level. The device may include an analog-to-digital converter (ADC) to convert an input signal into digital samples at time intervals, a receiver to generate a pulse-per-second (PPS) signal, an oscillator to generate an oscillator signal, and a data processor coupled to the ADC, the receiver, and the oscillator. The data processor may include a counter to measure an oscillator frequency of the oscillator signal at each pulse of the PPS signal, an adjuster to adjust a timer period register value, and a timer to adjust the time intervals based on the adjusted timer period register value. Based on the digital samples, the data processor may generate a plurality of metrics, which may include one or more measurements of frequency, magnitude, phase, harmonic level, signal-to-noise ratio, sag, and swell of the input signal.
1. A device, comprising:
an analog-to-digital converter (ADC) to convert an input signal into digital samples, wherein the ADC is configured to receive the input signal from a power grid;
a receiver to generate a pulse-per-second (PPS) signal, wherein the ADC is configured to convert the input signal into the digital samples at each of a plurality of sampling times, the plurality of sampling times being distributed between two consecutive PPS signals;
an oscillator to generate an oscillator signal having an oscillator frequency (f osc ); and
a data processor coupled to the ADC, the receiver, and the oscillator, wherein the data processor is configured to:
receive the oscillator frequency and a sampling rate (F s ) and calculate an ideal timer period register value (N ideal ) which is a number of cycles of oscillator signal between two sampling times;
calculate a timer period register value (N i ) for each two consecutive sampling times distributed between two consecutive PPS signals, the timer period register value (N i ) for a period between an (i-1) and an ith sample is determined by:
N
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=
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and
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and
the first sample is taken at the PPS signal;
adjust the sampling times based on the timer period register value (N i ) to minimize deviation from the ideal timer period register value (N ideal );
sample the input signal at each adjusted sampling time; and
generate a plurality of metrics based on the digital samples.
2. The device of claim 1 , further comprising:
an input coupled to an outlet to receive the input signal from the outlet, wherein the plurality of metrics include one or more measurements of frequency, magnitude, phase, harmonic level, signal-to-noise ratio, sag, and swell of the input signal.
3. The device of claim 1 , wherein the data processor comprises:
a counter to measure the oscillator frequency at each pulse of the PPS signal;
an adjuster to adjust the timer period register value based on the measured oscillator frequency and the sampling rate; and
a timer to adjust, based on the adjusted timer period register value, the sampling times.
4. The device of claim 1 , further comprising:
a signal conditioner to reduce the magnitude of the input signal prior to the ADC converting the input signal into the digital samples.
5. The device of claim 1 , further comprising:
a management processor to time stamp the plurality of metrics based on a timestamp signal, wherein the timestamp signal is generated by the receiver.
6. The device of claim 1 , further comprising:
a transceiver to transmit the plurality of time-stamped metrics to a data center.
7. The device of claim 1 , further comprising:
a display module to display the plurality of time-stamped metrics.
8. A device, comprising:
a first input to receive an oscillator signal from an oscillator;
a second input to receive a pulse-per-second (PPS) signal from a receiver;
an output coupled to an analog-to-digital converter (ADC);
a counter to measure an oscillator frequency (f osc ) of the oscillator signal between two consecutive pulses of the PPS signal;
an adjuster to adjust a timer period register value (N i ) based on the oscillator frequency (f osc )and a sampling rate (F s )of the device; and
a timer to adjust, based on the adjusted timer period register value, a plurality of sampling times between the two consecutive pulses of the PPS signal;
wherein:
the ADC converts an input signal into digital samples at each of the plurality of sampling times;
the adjuster is configured to, based on the oscillator frequency (f osc ) and the sampling rate (F s ), calculate an ideal timer period register value (N ideal ) which is a number of cycles of oscillator signal between two sampling times;
the adjuster is configured to adjust the timer period register value (N i ) for each two consecutive sampling times distributed between the two consecutive PPS signals to minimize deviation from the ideal timer period register value (N ideal ), the adjusted timer period register value (N i ) of the data processor for a period between an (i-1) and an ith sample is determined by:
N
i
=
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N
L
(
if
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=
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where
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osc
F
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)
and
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H
=
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(
f
osc
F
s
)
;
and
the first sample is taken at the PPS signal.
9. The device of claim 8 , wherein, between two consecutive pulses of the PPS signal, the timer period register value is on average equal to the oscillator frequency divided by the sampling rate.
10. The device of claim 8 , wherein a first digital sample of the digital samples between two consecutive pulses of the PPS signal is synchronized to the PPS signal.
11. The device of claim 8 , further comprising:
a data queue module to store the digital samples from the ADC; and
a calculation module to generate a plurality of metrics based on the digital samples stored in the data queue module.
12. The device of claim 11 , wherein the plurality of metrics include one or more measurements of frequency, magnitude, phase, harmonic level, signal-to-noise ratio, sag, and swell of the input signal.
13. A method, comprising:
converting an input signal into digital samples at each of a plurality of sampling times, wherein the input signal is received from a power grid; and
adjusting the sampling times between two consecutive pulses of a pulse per second signal based on the pulse-per-second (PPS) signal generated by a receiver;
wherein adjusting comprises:
measuring an oscillator frequency (f osc ) of an oscillator;
calculating an ideal timer period register value (N ideal ), which is a number of cycles of oscillator signal between two sampling times, based on the oscillator frequency (f osc ) and a sampling rate (F s );
adjusting a timer period register value (N i ) for each two consecutive sampling times distributed between the two consecutive PPS signals to minimize deviation from the ideal timer period register value (N ideal ), the timer period register value (N i ) for a period between an (i-1) and an ith sample is determined by:
N
i
=
{
N
L
(
if
∑
k
=
2
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-
1
(
N
k
)
+
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L
-
(
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-
1
)
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ideal
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=
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-
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N
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+
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ideal
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H
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k
)
+
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-
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ideal
)
,
i
≥
3
round
(
f
osc
F
s
)
,
i
=
2
where
N
L
=
floor
(
f
osc
F
s
)
and
N
H
=
ceiling
(
f
osc
F
s
)
;
and
the first sample is taken at the PPS signal.
14. The method of claim 13 , further comprising:
reducing the magnitude of the input signal prior to converting the input signal into digital samples.
15. The method of claim 13 , wherein measuring the oscillator frequency comprises:
receiving an oscillating signal from the oscillator;
receiving the PPS signal from the receiver; and
counting a number of cycles of the oscillating signal between two consecutive pulses of the PPS signal.
16. The method of claim 13 , further comprising:
storing the digital samples in a data queue module; and
generating a plurality of metrics based on the digital samples stored in the data queue module.
17. The method of claim 16 , wherein the plurality of metrics include one or more measurements of frequency, magnitude, phase, harmonic level, signal-to-noise ratio, sag, and swell of the input signal.
18. The method of claim 16 , further comprising:
time stamping the plurality of metrics based on a timestamp signal generated by the receiver.
19. The method of claim 16 , further comprising:
transmitting the plurality of time-stamped metrics to a data center.
20. The method of claim 16 , further comprising:
displaying the plurality of time-stamped metrics on a display module.