Granted Patent B2

US 8,183,852 · App. 12/587,516 · Granted May 22, 2012

Abstract

Claims (28)

1. An apparatus for determining AC voltage waveform anomalies, comprising:

a threshold generator for generating at least one time-variant threshold based on information regarding an AC voltage waveform; and

a threshold detector for comparing a sample of the AC voltage waveform to the at least one time-variant threshold to identify an AC voltage waveform anomaly.

2. The apparatus of claim 1 , wherein the information comprises an amplitude, a phase, and a frequency of the AC voltage waveform.

3. The apparatus of claim 1 , wherein the at least one time-variant threshold comprises a first and a second time-variant threshold.

4. The apparatus of claim 3 , wherein the first and the second time-variant thresholds encompass an expected level of the AC voltage waveform.

5. The apparatus of claim 1 , wherein the threshold detector identifies a failure when a first number of AC voltage waveform anomalies are identified from a second number of samples of the AC voltage waveform.

6. The apparatus of claim 5 , wherein the threshold detector generates a signal for deactivating a power conversion as a result of identifying the failure.

7. The apparatus of claim 3 , wherein the first and the second time-variant thresholds are boundless at expected zero-crossings of the AC voltage waveform.

8. The apparatus of claim 1 , wherein the at least one time-variant threshold comprises (i) an upper bound of (1+K 1 )*V AC sin(ωt)+K 2 *sign[Φ], and (ii) a lower bound of (1−K 1 )*V AC sin(ωt)−K 2 *sign[Φ], wherein K 1 and K 2 are offset values, V AC is an amplitude of the AC voltage waveform, ω is a frequency of the AC voltage waveform, t is a time, Φ is a phase of the AC voltage waveform, sign[Φ]=1 for 0<Φ<π, and sign[Φ]=−1 for −π<Φ<0.

9. A method for determining AC voltage waveform anomalies, at least a portion of the method being performed by a computing system comprising at least one processor, the method comprising:

computing at least one time-variant threshold based on information regarding an AC voltage waveform; and

comparing a sample of the AC voltage waveform to the at least one time-variant threshold to identify an AC voltage waveform anomaly.

10. The method of claim 9 , further comprising:

obtaining a plurality of samples of the AC voltage waveform; and

determining an amplitude, a phase, and a frequency of the AC voltage waveform based on the plurality of samples for computing the at least one time-variant threshold.

11. The method of claim 9 , further comprising identifying a failure when a first number of AC voltage waveform anomalies are identified from a second number of samples of the AC voltage waveform.

12. The method of claim 11 , further comprising generating a signal for deactivating a power conversion as a result of identifying the failure.

13. The method of claim 9 , wherein the at least one time-variant threshold comprises a first and a second time-variant threshold.

14. The method of claim 13 , wherein the first and the second time-variant thresholds encompass an expected level of the AC voltage waveform.

15. The method of claim 13 , wherein the first and the second time-variant thresholds are boundless at expected zero-crossings of the AC voltage waveform.

16. The method of claim 9 , wherein computing the at least one time-variant threshold comprises computing (i) an upper bound of (1+K 1 )*V AC sin(ωt)+K 2 *sign[Φ], and (ii) a lower bound of (1−K 1 )*V AC sin(ωt)−K 2 *sign[Φ], wherein K 1 and K 2 are offset values, V AC is an amplitude of the AC voltage waveform, ω is a frequency of the AC voltage waveform, t is a time, Φ is a phase of the AC voltage waveform, sign[Φ]=1 for 0<Φ<π, and sign[Φ]=−1 for −π<Φ<0.

17. The method of claim 12 , further comprising resuming the power conversion subsequent to a reset period.

18. Apparatus for determining AC voltage waveform anomalies, comprising:

means for computing at least one time-variant threshold based on information regarding an AC voltage waveform; and

means for comparing a sample of the AC voltage waveform to the at least one time-variant threshold to identify an AC voltage waveform anomaly.

19. The apparatus of claim 18 , further comprising means for identifying a failure when a first number of AC voltage waveform anomalies are identified from a second number of samples of the AC voltage waveform.

20. The apparatus of claim 19 , further comprising means for generating a signal for deactivating a power conversion as a result of identifying the failure.

Assignments (6)