Cyber-Physical Energy SystemsLECTURE 3

PRINCIPLES OF MODELING FOR CYBER-PHYSICAL SYSTEMS

INSTRUCTOR: MADHUR BEHL

Principles of modeling for CPS – Fall 2018 MADHUR BEHL - MADHUR.BEHL@VIRGINIA.EDU 1

Tea Time In Britain

Principles of modeling for CPS – Fall 2018 MADHUR BEHL - MADHUR.BEHL@VIRGINIA.EDU 2

Peaks occur during major sporting events

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Price Volatility: Summer peak

20th, July 2015

Nominal price: $25/MWh Peak Price: $800/MWh

32x!

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Price volatility is the new normalPJM (ISO) Locational Marginal Prices (LMPs) example

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Peak Demand is Expensive!

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Peak Demand is Expensive!

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Peak Demand is Expensive!

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Total electricity generation capacity in U.S. 1190 GW

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Total electricity generation capacity in U.S. 1190 GW

1 Large Hadron ColliderPeak demand

200 MW

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Total electricity generation capacity in U.S. 1190 GW

1 Large Hadron Collider

Peak demand

200 MW

5,950LHCs

Running at the same time

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10,000,000 simultaneous superchargers at peak capacity

“All kilowatts are not created equally”

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Demand Response

Reliable

Clean

Cost-Effective

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Imagine getting paid for doing nothing

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Imagine getting paid for doing nothing

NIGERIAN

MAIL SCAM

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Imagine getting paid, or otherwise compensated, for not using electricity during peak hours!

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A Demand Response EventEl

ectr

icity

Load

(GW

)

Peak anticipateddue to forecast

Electricity Load Increases

Demand ResponseDispatch

DR Curtailment

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Demand Response – Looks familiar

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Q) If you don’t know what's going to happen when you change a set-point. How do you even know the change is worth making ?

Q) What is the best change that you can make right now ?

Model-based predictive control (MPC)

What kind of models ?

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The control problem in buildings

Integrated control of:

• Heating

• Cooling

• Ventilation

• Lighting

• Blinds

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Model Predictive Control (MPC)

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Generation, Transmission, Distribution: Supply-side

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Modeling the grid dynamics ?

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Modeling the grid dynamics ? Not in this course.

IEEE 39 New England Power Grid Model

• 39 transmission buses• 10 generators

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Electricity consumption Buildings: Demand-side

Commercial, Industrial & Institutional (C/I/I) Resedential

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Why Buildings ?

Portion of global energy use

Portion of electricity consumption in the United States

Portion of global total CO2 emissions

40%70%1/3

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Electricity use due to cooling,

lighting and ventilation62% Portion of natural gas use dedicated to space heating 86%

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How are building models obtained today ?

White Box

1/Ugw

1/Ugi

1/Ugo

Cgo

Cgi

Tgo

Tg

Tgi

Tz

Q.rad,e

1/Uei1/Uew1/Ueo

Ceo Cei

Ta

Teo Tei

Q.sol,e

Q.solt/2

1/Uci

1/Ucw

1/UcoCci

Cci

Ta

Q.sol,c

Q.rad,c

Ta

Q.conv + Q.

sens

1/Uii 1/Uiw 1/Uio

Cii Cio

Tci

Tco

1/Uwin Tii Tio

Q.solt/2

Q.rad,g

[ExternalWalls]

Ti

[Ceiling]

[Floor]

[InternalWalls]

[Windows]

Grey Box

Black Box

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How are building models obtained today ?

White Box

Grey Box

Black Box

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White-Box Modeling

Hire building modeling experts

Set parametersFloor by floorZone by zoneWall by wall

Layer by layerEquipment by

equipmentTransfer geometry

Floor PlanHVAC layout

Not always

available

Guess nominalparameter

values

First principles based building energy simulation

Model TuningData

Sensor retrofits

Principles of modeling for CPS – Fall 2018 MADHUR BEHL - MADHUR.BEHL@VIRGINIA.EDU 33

White-Box Modeling

Hire building

modeling

experts

Set parametersFloor by floor

Zone by zone

Wall by wall

Layer by layer

Equipment by

equipment

Transfer geometry

Floor PlanHVAC layout

Not always

available

Guess nominalparameter

values

First principles based

High fidelity

Building energy simulation

Model TuningData

Sensor retrofits

Cost and time prohibitive(sensor installation, commissioning & expertise)

Not suitable for model-based controlModel complexity and uncertainty, (1000’s parameters and states)

Principles of modeling for CPS – Fall 2018 MADHUR BEHL - MADHUR.BEHL@VIRGINIA.EDU 34

How are building models obtained today ?

White Box

1/Ugw

1/Ugi

1/Ugo

Cgo

Cgi

Tgo

Tg

Tgi

Tz

Q.rad,e

1/Uei1/Uew1/Ueo

Ceo Cei

Ta

Teo Tei

Q.sol,e

Q.solt/2

1/Uci

1/Ucw

1/UcoCci

Cci

Ta

Q.sol,c

Q.rad,c

Ta

Q.conv + Q.

sens

1/Uii 1/Uiw 1/Uio

Cii Cio

Tci

Tco

1/Uwin Tii Tio

Q.solt/2

Q.rad,g

[ExternalWalls]

Ti

[Ceiling]

[Floor]

[InternalWalls]

[Windows]

Grey Box

Black Box

Principles of modeling for CPS – Fall 2018 MADHUR BEHL - MADHUR.BEHL@VIRGINIA.EDU 35

Grey-Box [Inverse] Modeling

Hire building

modeling

experts

Set parametersFloor by floor

Zone by zone

Wall by wall

Layer by layer

Equipment by

equipment

Transfer geometry

Floor PlanHVAC layout

Not always

available

Guess nominalparameter

values

Parameter Estimation

Data

Sensor retrofits

Lumped Parameter

‘RC’ model

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Grey-Box Modeling: ‘RC’ networks

Discrete-Time State Space Model:(parameterized by θ)

States (All node temperatures): x = [Teo, Tei, Tco, Tci, Tgo, Tgi, Tio, Tii, Tz]T

Inputs (Disturbances and Control): u = [Ta, Tg, Ti, Qsole, Qsolc, Qrade, Qradc, Qradg, Qsolt, Qconv, Qsens]T

Parameter Estimation: Least Squares Error

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Heating, Ventilation, & Air Conditioning

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HVAC is everywhere.. It is all around us,Even now, in this very room,You can feel it, ..when you go to work,

..when you go home

..when you pay your electricity bill

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Its all about comfort..

Temperature

Humidity

Pressure

Ventilation

68°F (20°C) and 75°F (25°C)

30% relative humidity (RH) and 60% RH

A slightly positive pressure to reduce outside air infiltration.

Rooms typically have several complete air changes per hour

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Components of HVAC System

5 system loops..

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Air handling systems

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Air handling systems

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Air handling system

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Air handling unit

Outside air Supply air

Return air

Exhaust air

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Air handling unit

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Air terminals: Constant Air Volume (CAV)

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Air terminals: Variable Air Volume (VAV)

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Ceiling plenum returnThe plenum is the space between the ceiling and the roof, or floor, above.

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Air-Water interface- Heat exchanger.

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Chilled water loop

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Chiller plants

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Just chilling as a grad student…

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my biggest fans…

Chiller plants

4 million gallons of water at 42

degree Fahrenheit

26 MW peak load

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Cooling towers

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Meeting zone loads

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Control loops

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Local control loops

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Local control loops

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Next lecture..

Creating a dynamical system model of a zone.

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