power factor signature analysis - stanford...
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Power Factor Signature Analysis
For Device Identification Applications
Dane Kouttron, Rensselaer Polytechnic
To provide detailed usage info to the user via signal disambiguation
Constantly monitors residential power usage for transients and eventsMeters similar characteristics as existing smart meter technology
Per phase voltage Per phase current consumption
Device Identification Overview
Dane Kouttron, Sept. 20082
Example: what does an incandescent lamp look like?
Video clip displays consumption Look at transient characteristicsNotice anything interesting?
Device Identification Overview
Dane Kouttron, Sept. 20083
Basic Process OverviewIncandescent Bulb warm up transient vs CFL bulb warm up transient (current consumption)
Upon ‘event’ occurrence, ‘fingerprints’ can be isolatedFingerprint characteristics are based on P, Q and Harmonic monitoringR-squared statistical analysis used to match ‘fingerprints’ and known files from the ‘encyclopedia’
Device Identification Process Overview
CFL
Incandescent
Event occurrence R Squared probability Device ID
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Example test applicationUnit constantly searching for ‘events’Displays list of devices in use on circuit (based on known / stored fingerprint characteristics)Able to identify small devices (refrigerator lamp)
Device Identification Overview
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Analyzing Common OccurrencesHarmonic Response
(CFL turn on transient, greatly reduced speed)Peaks indicate harmonic disturbance and harmonic characteristic of deviceSeparate controller used as harmonic interrupt
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Device Identification Hardware OverviewAnalog Inputs:
Per phase voltagePer phase currentAmplified Harmonic input
Processing:AVR Xmega series Micro controller
Harmonic InterruptsAVR Mega 168 series Microcontroller
Networking Requirements:Serial interfaced networking platform (pre-existing hardware repurposed for internet communications)
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Hardware Requirements For PFS Processing- upwards of 70 MIPS (single core)
[equivalent to low end smart-phone processor]
Storage-Onboard of 4mb for cache / swap space
Transmission-Dependant on required resolution / update frequency.
[realtime = ~ 12 mb of data tx / 3 weeks, assuming 100 known devices]
All PFS computations to be completed on client side
Resolution of the data-12 bits minimum sampling resolution
Sampling frequency vs accuracy plot30kHz minimum sampling frequency
Dane Kouttron, Sept. 20088
Device Identification Hardware: AnalogAnalog Inputs:
Current ClampsProvide moderate frequency response of current consumptionRelatively expensive
Voltage InputResistive Voltage divider (no induced phase shift), excellent frequency responseLow cost
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Device Identification Hardware: DigitalTwo microcontrollers implemented
Hardware (band pass) filtering for harmonics Harmonic interrupt subroutines run in parallel to PFS processing
Shared real time clockSwap space / ‘encyclopedia’ spaceAnalog inputs are digitally adjustable for variability in current clamps used
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Device Identification Hardware: Communications
Currently using existing commercial WIFI transceivers reprogrammed for communication backboneCan be redesigned to incorporate other communication protocols
Serial connected phone modemBluetooth phone connectionEthernet
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Device Identification Software:Software Design
Triggering system for event occurrence
Triggering dependant on change in real and reactive powerTriggering also interrupted by harmonic events
(hardware FFT)
ComparisonProbability analysis using R-squared regression
Prototype testing in Labview
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User FeedbackClient side Feedback
Email updates (tabulated client side) can be sent directly from devicePreset timing interval could trigger sequential updates along with real time data / accessibility
Web based interfaceCell phone updates
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Questions / Comments
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