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Fakultät Informatik – Institut für Systemarchitektur – Professur Rechnernetze

Design and Implementation of aHigh‐Fidelity AC Metering Network

Presenter: Marco ZulkowskiSupervisor: Dr.-Ing. habil. Waltenegus DargieTU DresdenChair of Computer Networks

Outline • Motivation• Energy Metering

– Software– Hardware– I-To-V Conversion

• Shunt Resistor• Current Transformer• Hall-Effect Sensor

• Hardware Design– ACme – A– AC – Control– Epic Core

• Network– Architecture– Routing– Edge Router

• Application TierFolie 2

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Motivation

• Enable interactive, near real-time monitoring of small and large loads in an office environment

• Understanding the electricity usage patterns and alter the behavior to reduce the energy footprint of occupants

• Quick deployment

Outline • Motivation• Energy Metering

– Software– Hardware– I-To-V Conversion

• Shunt Resistor• Current Transformer• Hall-Effect Sensor

• Hardware Design– ACme – A– AC – Control– Epic Core

• Network– Architecture– Routing– Edge Router

• Application TierFolie 4

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Energy Metering

• Process of calculating the power and energy from the current and voltage

• Current needs to be converted into a voltage (I-To-V Conversion)• Calculation can be done in either software or hardware

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Energy Metering in Software

• No dedicated IC is needed• Only a single wire connects the output of I-To-V Conversion to

the ADC of the µC• µC must sample the signal, multiply and accumulate in software• Keeps the µC busy performing the sampling• Results are less precise due to lower sampling rates• Assumes constant RMS Voltage

[4]

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Energy Metering in Hardware

• Dedicated IC is used, here ADE7753• Two 16 bit ADC's• Internally integrates power to produce energy• Provides extensive filtering and includes temperature sensors• Stores power and energy measurement in registers• Communicates with the µC via SPI Bus

– Simplifies data aquisition process– Allows µC to easily configure parameters in the IC

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Energy MeteringI–To–V Conversion: Shunt Resistor

• Resistor (very small resistance) in series with the Load• Voltage drop (very small) is propotional to the current• Inexpensive and precise• Voltage drop may effect the AC device's with high power draw• Heating of the resistor :

– Thermal design concerns– Measurement issues, resistance is propotional to temperature

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Energy MeteringI–To–V Conversion: Current Transformer

• In-Line Single Phase Current Transformer• Voltage drop across Burden Resistor is propotional to the current• Large in size and weight• expensive

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Energy MeteringI–To–V Conversion: Hall Effect Sensor

• Hall Effect :– A conductor in a magnetic field

produces a voltage depending on the current flow and the strength of the magnetic field

[1]

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Energy MeteringI–To–V Conversion: Hall Effect Sensor

• A magnetic field created by the current is measured with a Hall Effect Sensor

• The magnetic field from a coil is directly proportional to the product of the number of turns in the coil and the current flowing through the coil

[2]

Outline • Motivation• Energy Metering

– Software– Hardware– I-To-V Conversion

• Shunt Resistor• Current Transformer• Hall-Effect Sensor

• Hardware Design– ACme – A– AC – Control– Epic Core

• Network– Architecture– Routing– Edge Router

• Application TierFolie 12

Hardware DesignACme - A

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Hardware DesignACme - A

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Hardware DesignACme – A Board

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Hardware DesignAC - Control

• Solid State Relay, no electromagnetic relay• Maximum switchable current :15A (1.8kW @ 120V)• Near infinity switching lifetime• High switching speed• Small in size

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Hardware DesignEpic Core

• Full-featured mote in a compact form factor• Fully-supported platform under TinyOS• Including a low-power microcontroller, IEEE 802.15.4-compatible

radio, 16-Mbit flash memory

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Hardware DesignEpic Core

• Microcontroller MSP 430– 8 12 bit ADC– Flash 48 KB, RAM 10 KB

• Radio CC2420– 2.4 GHz IEEE 802.15.4 compatible– Effective data rate of 250 kbps – Connected via SPI to the µC– PCB PIFA

• Atmel 16 Mbit Flash– Shares SPI with Radio

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Hardware DesignSummary

Outline • Motivation• Energy Metering

– Software– Hardware– I-To-V Conversion

• Shunt Resistor• Current Transformer• Hall-Effect Sensor

• Hardware Design– ACme – A– AC – Control– Epic Core

• Network– Architecture– Routing– Edge Router

• Application TierFolie 20

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NetworkArchitecture

• Developed an implementation of IPv6 for TinyOS called „blip“• ACme nodes create an IPv6 subnet• The network consists of edge routers and sensor nodes• Edge routers are nodes with external connectivity

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NetworkRouting

• Reliable multihop communication within the subnet• Packets can be routed between endpoints in the same subnet,

or be delivered to a gateway• Each sensor node functions as an IProuter

– chooses a set of default routes based on router advertisement– Link-layer retransmission– edge routers advertises a cost of zero

• The sensor nodes observe the subnet to enable communication with individual devices

– This is reported to an edge router (topology update message)– The edge routers form paths back into the network

• Packets into the network are source routed from the edge router to a particular node

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NetworkEdge Router

• Using two existing linux-class devices– The Meraki Mini, and– The Open Mesh Mini Router

• Both export internally a single serial portwhich is used to add an 802.15.4 radio

• All edge routers join an IPv6 multicast group– to forward topology updates to the group

Meraki Mini with Epic Open Mesh with Epic

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NetworkTopology Snapshot

Outline • Motivation• Energy Metering

– Software– Hardware– I-To-V Conversion

• Shunt Resistor• Current Transformer• Hall-Effect Sensor

• Hardware Design– ACme – A– AC – Control– Epic Core

• Network– Architecture– Routing– Edge Router

• Application TierFolie 25

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Application TierTopology

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Application TierTopology

• Consists of:– Web front – end – Database back – end

• Built atop the network of nodes and is logically distinct from the nodes and the network

– Allows distinct applications to use the underlying network concurrently

• Applications perspective:– Each ACme exposes operations to configure and report its

measurements over UDP using a simple binary format

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Application TierWebinterface

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References

[0] Jiang, X., Dawson Haggerty, S., Dutta, P., and Culler, D. 2009. Design ‐and implementation of a high fidelity AC metering network. In ‐Proceedings of the 2009 international Conference on information Processing in Sensor Networks (April 13 16, 2009). Information ‐Processing In Sensor Networks. IEEE Computer Society, Washington, DC, 253 264.‐

[1] Honeywell - HALL EFFECT SENSING AND APPLICATIONFigure 2-2 Hall effect principle, magnetic field present

[2] Honeywell - HALL EFFECT SENSING AND APPLICATIONFigure 5-16 Current sensor with pole pieces

[3] http://www.moteware.com/pub-docs/datasheet-epic.pdf[4] M. João Sepúlveda Freitas, João L. Afonso, Júlio S. Martins, „A SINGLE-PHASE POWER SERIES COMPENSATOR FOR VOLTAGE

DISTORTION“, Department of Industrial Electronics, University of Minho, Portugal, Figure 1