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Topic 4: Demand Response A.H. MohsenianRad (U of T) 1 Networking and Distributed Systems Department of Electrical & Computer Engineering Texas Tech University Spring 2012
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Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

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Page 1: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Topic 4: Demand Response

A.H. Mohsenian‐Rad (U of T) 1Networking and Distributed Systems

Department of Electrical & Computer EngineeringTexas Tech University

Spring 2012

Page 2: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Residential Load Profile

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• A typical residential load profile with and without PHEVs in California:

Resid

entia

l Load Profile (C

al. Edison)

2

Page 3: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Residential Load Profile

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• The overall load profile in various days in the state of Texas:

• The overall load may significantly change during the day and week.

Source: ERCOT

3

Page 4: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Residential Load Profile

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• The practical load profile is very unbalanced:

• Residential Peak Load (afternoon)

• Industrial / Office Peak Load (morning)

• We define:

• Peak-to-average ratio (PAR):

• It is desirable to have PAR close to 1. (Q: Why?)

LoadDaily AverageLoadDaily Peak

4

Page 5: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Definition of Demand Response

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• According to the U.S. Department of Energy:

Demand response (DR) is defined as changes inelectric usage by end‐use customers from theirnormal consumption patterns in response tochanges in the price of electricity over time, or toincentive payments designed to induce lowerelectricity use at times of high wholesale marketprices or when system reliability is jeopardized.

Q: What is the difference between DR and Load Shedding done by utility?

5

Page 6: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Two Approaches to Demand Response

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid 6

• There are two general approaches to DR:

• Direct Load Control (DLC)

• Indirect Load Control / Pricing

• Direct load control programs have been around for decades.

• Q: What is the difference between the two approaches?

Page 7: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

DLC

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid 7

• In DLC:

• The utility has remote access to certain load of users

• Air conditioner

• Water heater.

• It remotely turns on or off the load when ever needed.

• DLC is tried to be transparent to users. (Q: Why?)

Page 8: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

DLC Example

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid 8

• Baltimore Gas and Electric (BGE) has been involved in DLC:

• Since April 1988.

• For residential and small commercial customers

• Participants/users are offered $10 per months

• During the summer: June ‐ September

• BGE installed DLC switches on air conditioner

Page 9: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

DLC Example

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid 9

• Baltimore Gas and Electric (BGE) has been involved in DLC:

• Compressor cycle is controlled remotely:

• To operate a max of 30 min at any one time.

• In 1990, they also added DLC for water heaters.

• Currently [after 20 years]:

• The program has about 250,000 customers enrolled

Page 10: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

DLC Example

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid 10

• The DLC program in the city of New Bern, NC:

• Total number of residential customers: 17,210

• Total DLC participants: 10,500 (61%).

• Key idea:

• Reduce the load at peak hours.

• DLC programs require special equipment and maintenance.

Page 11: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Smart Pricing

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid 11

• An alternative for DLC is smart pricing.

• Instead of directly controlling customers’ load,

• Let them know about the price changes:

• They will naturally try to avoid higher price hours:

• This will reduce the load at peak hours.

• Users are directly involved in decision making.

Page 12: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Smart Pricing Models

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Time-of-Use (TOU) Pricing in Toronto, Ontario:

Summer                                                   Winter

12

Page 13: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Smart Pricing Models

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Day-Ahead Pricing (DAP) / Real-Time Pricing (RTP) in Chicago, IL:

December 15, 2009

13

Page 14: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Smart Pricing Models

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Inclining Block Rates (IBR) in Vancouver, British Columbia:

December 15, 2009

Q: What is the benefit of using IBR?

14

Page 15: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Closer Look at DAP

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• The overall daily trend is somehow the same over the past few years:

• We have higher prices at peak load hours. (Q: Why?)

December 15, 2009

15

Page 16: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Closer Look at DAP

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Prices can change at different months of the year:

• In Chicago, the prices are higher in Winter. (Q: Why?)

December 15, 2009

16

Page 17: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Closer Look at DAP

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Prices are different on week days vs. weekend.

• The prices are usually less on weekends. (Q: Why?)

December 15, 2009

17

Page 18: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Closer Look at DAP

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Today’s price is usually correlated with prices on previous days:

• Q: Can you explain why the correlations are like this?

December 15, 2009

18

Page 19: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Informing Users

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• The users should be informed about prices (price changes): 

• Utility Website

• Email

• Text Message

• Automated Voice Calls

• Energy Orbs [We will learn about it soon]

• Smart Meter

19

Page 20: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Informing Users

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Energy Orb: A Light to Visualize Electricity Consumption.

• Used by BGE, PJM, …

• BGE Setup: 

– Colors: Green, Yellow, and Red

– They indicate off‐peak, mid‐peak, and on‐peak hours.

• People react to price changes and reduce consumption.

• Saved each user an average or $100 on the summer bill!

20

Page 21: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Informing Users

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• PJM Energy Orb Codes: Alert Users about DR Events.

Ref: www.pjm

.com

21

Page 22: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Informing Users

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• PJM Energy Orb Codes: Alert Users about DR Events.

Ref: www.pjm

.com

22

Page 23: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

User Response

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Q: Can users/consumers properly react/respond to smart pricing?

• A: Not Really!

• Reason 1) Too much information to follow!

• In Chicago users did not have time to check the real‐time prices. 

• Reason 2) Complicated Decision Making.

• Think of a combined RTP and IBR model!!!

• The “Energy Orb” is not enough! We need more…

23

Page 24: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

User Response

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• An interesting commercial product is Energy Detective(R): 

Source: www.theenergydetective.com

24

Page 25: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

User Response

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• It can be interfaced with your PC or Smart Phone: 

Source: www.theenergydetective.com

25

Page 26: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

User Response

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Provides users with analyzed information about:

• Real time power consumption measurements

• Real time electricity price values 

• It is essentially interfaced with Smart Meter to obtain such info.

• It can also support behind‐the‐meter renewable generation.

• More Info: http://www.theenergydetective.com/support/installation

26

Page 27: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Energy Consumption Scheduling

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Energy Orb, Energy Detective, and similar products:

• Can help users understand smart pricing and DR

• But DR decision making can still be difficult task for users.

• Solution: Automated Energy Consumption Scheduling (ECS)

• Could be Part of Smart Meter

• Could be Part of Energy Detective Device

• Could be a Separate Device

27

Page 28: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Energy Consumption Scheduling

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Smart meter with an embedded ECS:

• : Energy consumption schedule for appliance a.

User’s Energy Needs

Communications InfrastructurePower Infrastructure

ax

28

Page 29: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Energy Consumption Scheduling

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Smart meter with an embedded ECS:

• : Energy consumption schedule for appliance a.

User’s Energy Needs

Communications InfrastructurePower Infrastructure

ax

Price Information

29

Page 30: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Energy Consumption Scheduling

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Smart meter with an embedded ECS:

• : Energy consumption schedule for appliance a.

User’s Energy Needs

Communications InfrastructurePower Infrastructure

ax

30

Page 31: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Energy Consumption Scheduling

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Smart meter with an embedded ECS:

• : Energy consumption schedule for appliance a.

User’s Energy Needs

Communications InfrastructurePower Infrastructure

ax

31

Page 32: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Energy Consumption Scheduling

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Smart meter with an embedded ECS:

• : Energy consumption schedule for appliance a.

User’s Energy Needs

Communications InfrastructurePower Infrastructure

ax

32

Page 33: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Energy Consumption Scheduling

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Simple Example: Dishwasher (after lunch):

33

Page 34: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Energy Consumption Scheduling

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Another Example: A Parked Electric Vehicle:

Discharge

Q: Why would you ever want to discharge your battery?

34

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Energy Consumption Scheduling

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• ECS Devices should:

• Be Compatible with Smart Appliances

• Be Easy‐to‐understand and Easy‐to‐use

• Be Plug‐and‐Play

• Satisfy users’ energy consumption needs

• Help reduce not only PAR but also users’ bills (Q: Why?)

35

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ECS Decision Making

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Q: Given the price values how should ECS schedule the load?

• ECS should have CPU/Microcontroller to analyze:

– Price values

– User’s energy consumption needs

• The schedule should basically be an optimal solution

– To minimize the cost while maintain comfort. 

36

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ECS Decision Making

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Let A denote the set of appliances:

• Washer, Dryer, Dish‐washer, PHEVs, …

• For each appliance a ∈ A, we define an energy consumption scheduling vector xa as follows:

• where H ≥ 1 is the scheduling horizon that indicates the number of hours ahead which are taken into account for decision making in energy consumption scheduling (H = 24).

],,[ 1 Haaa xxx

37

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ECS Decision Making

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• A real‐valued scalar               denotes the corresponding one‐hourenergy consumption that is scheduled for appliance a ∈ A. 

• Let Ea denote the total energy needed for the operation of appliance a ∈ A.

• PHEV: Ea = 16 kWh to charge the battery for a 40‐miles driving range

• Front‐loading washing machine: Ea = 3:6 kWh per load

• Q: Other examples? 

0hax

38

Page 39: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• For each a ∈ A, the user should indicate: 

• αa: Beginning of the acceptable operation time. 

• βa: End of the acceptable operation time (deadline).

– Dish washer after lunch table: 

αa = 2 PM and βa = 6 PM (make dishes ready for dinner)

– PHEV after plugging in at night: 

αa = 10 PM and βa = 7 AM (make PHEV ready in the morning)

39

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ECS Decision Making

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• The ECS should finish operation for appliance a ∈ A by deadline.

• Operation should be scheduled within interval [αa,βa]

• Given the pre‐set parameters Ea, αa, and βa, it is required that

• It is also required:                 for any h < αa and h > βa. (Q: Why?)

., AaEx ah

ha

a

a

0hax

40

Page 41: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Each appliance a ∈ A usually has a maximum power level          .

• PHEV: May be charged only up to               = 3.3 kW per hour

• Each appliance a ∈ A may also have a minimum power level .

• Therefore, for each appliance a ∈ A , it is required that

],[,maxminaaa

haa hx

maxa

maxa

mina

41

Page 42: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Depending on the type of meter and load subscription:

• We may need to limit the total hourly load: 

• Q: Is there any other constraint that we should consider?

• [For PHEVs, for now, we do not consider discharging]

.,,1,max HhExAa

ha

42

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ECS Decision Making

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Putting these constraints together

• We can introduce a feasible scheduling set for the ECS: 

.,,1,

],,[,,0

],,[,,

,,

max

maxmin

HhEx

hAax

hAax

AaExxX

Aa

ha

aaha

aanhan

ah

ha

a

a

43

Page 44: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Any energy consumption schedule              is acceptable for user.

• Acceptable in terms of fulfilling the user’s energy needs: 

• Q: Do we have any preference over a particular schedule? 

• Some of the ECS design objective:

• Minimize the cost of electricity

• Maximize user’s comfort

Xx

Tradeoff

44

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ECS Decision Making: Cost Minimization

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Let        denote the price of electricity at hour h.

• Could be RTP, TOU, DAP, etc. 

• Q: How can we calculate a user’s total daily cost of electricity? 

• [Assume that H = 24.]

hp

45

Page 46: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making: Cost Minimization

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Energy Consumption Scheduling Problem to Minimize Cost:

• Q: Is this a convex optimization problem? 

• You can use CVX to solve this problem.

• You can also implement the right code in a microcontroller. 

H

h Aa

ha

h

Xxxp

1min

46

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ECS Decision Making: Cost Minimization

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Q: What if IBR pricing tariffs are used by the utility? 

• Let                denote a DAP model with IBR as a function of load:

• Based on the choice of parameters ah, bh, and ch, the above pricing model reduces to DAP‐only or IBR‐only tariffs (Q: How?). 

)( hh lp

. if,

0 if,)( hhh

hhhhh

clbcla

lp

47

Page 48: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making: Cost Minimization

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Q: What is the ECS Problem to Minimize Cost for TOU+IBR prices?

• Q: Is this a convex optimization problem? 

• Q: Is the objective function differentiable?

Xxmin

48

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ECS Decision Making: Cost Minimization

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• We can plot the hourly payment at hour h with IBRs as follows:

49

Page 50: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making: Cost Minimization

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• The hourly payment is formed based on two intersecting lines:

and

• In fact, we have (Q: Why?)

hh laPayment

.)(Payment hhhhh cbalb

hhhhhhhhhh cbalblallp )(,max)(

50

Page 51: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making: Cost Minimization

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• The ECS Problem to Minimize Cost for TOU+IBR becomes:

• To get rid of max term, we introduce auxiliary variables :

• Next, we replace the above with multiple inequality constraints. 

H

h

hhh

Aa

ha

h

Aa

ha

h

Xxcbaxbxa

1)(,maxmin

hv

hhh

Aa

ha

h

Aa

ha

hh cbaxbxav )(,max

51

Page 52: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making: Cost Minimization

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• The ECS Problem to Minimize Cost for TOU+IBR becomes:

• The above problem is linear and differentiable: easy to solve. 

.,,1)(

,,,1,s.t.

min1

Hhvcbaxb

Hhvxa

v

hhhh

Aa

ha

h

h

Aa

ha

h

H

h

h

Xx

52

Page 53: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making: Optimization Trade-off

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• What if, we also incorporate user’s comfort in the model?

• For each appliance a ∈ A, user is OK: 

• If the job is done before the deadline βa.

• But he may still prefer if the job is done sooner.

• The preference is relative to how much extra money he may need to pay!

• Q: How can we model this trade‐off in the ECS optimization problem?

53

Page 54: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making: Optimization Trade-off

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• For each appliance a ∈ A, let us define: 

where  is selected by the user. 

• We have  (Q: Why?): 

],,[,)(aa

a

hah

a hE

a

1a

aaaa

54

Page 55: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making: Optimization Trade-off

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Example: Ea = 10, αa = 1, and βa = 10:

01.1a005.1a

001.1a

Q: Any idea how this can this model help us?

55

Page 56: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making: Optimization Trade-off

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• The new ECS Problem to find the optimal trade‐off:

• Parameter λcomfort is also set by the user. 

• Higher λcomfort: The user cares more about comfort than cost!

• Again, we can use auxiliary variables to solve this problem.

H

h Aa

ha

a

ha

comforthhh

Aa

ha

h

Aa

ha

h

Xxx

Ecbaxbxa

a

1

TermComfort TermCost

)()(,maxmin

56

Page 57: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making: Optimization Trade-off

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• For a typical residential load:

57

Page 58: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS Decision Making: Notifying Smart Appliances

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• One the optimal energy consumption schedule is obtained:

• The smart meter can talk to smart appliances over ZigBee WHAN.

58

Page 59: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• What we have seen so far applies to relative simple load types. 

• We also look at three other types of load: 

• PHEV with discharging to participate in V2G systems

• Air Conditioner

• Water Heater

• Demand Response can be more complicated for the these load.

59

Page 60: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Consider the case when a PHEV can discharge its battery:

• Clearly,            is no longer restricted to non‐negative numbers.

• The battery may not be discharged if it is empty.

• The battery may not be charged if it is full. 

• We need to add some additional constraints together with:

hax

., AaEx ah

ha

a

a

60

Page 61: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Let           denote the full charging capacity of the PHEV battery.

• Let          denote the initial charging level of the PHEV battery.

• The following constraints will fix the problem:

initaC

,,,,

,,,,

1initfull

1init

aaha

h

s

saaa

aaha

h

s

saa

hxxCC

hxxC

a

a

fullaC

61

Page 62: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Assume that              .

• For           , the constraints on last slide can be written as:

• Q: Why is it correct? 

1 ah

.initfull1initaaaa CCxC

1a

fullaC

initaC

0

62

Page 63: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• For           , the constraints become:

• Q: Why is it correct? 

• Scenario 1:                (Charge)

• Scenario 2:                (Discharge) 

21 ah

1initfull21initaaaaaa xCCxxC

01 ax

01 ax

fullaC

initaC

0

63

Page 64: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Once  an ECS can support discharging:

• The PHEV can participate in Vehicle‐to‐Grid (V2G) systems.

• V2G: Batteries of parked vehicles are used as source of power.

• The PHEVs discharge their battery when the grid lacks generation.

• The PHEVs are paid to compensate for their contribution.

• Each group of PHEVs is usually coordinated by an aggregator.

64

Page 65: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

V2G

65

Page 66: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Air Conditioner:

• For air conditioner, you do not have a need for a certain amount of power.

• Instead, you want to make sure that the indoor temperature 

– Remains as closely as possible to the set point by the user.

• Therefore, you are actually dealing with a closed‐loop control system.

• The key question is: 

– How can we relate energy consumption to the indoor temperature?

66

Page 67: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• We define:

• v: Indoor temperature

• ϵ: Thermal time constant of the building

• γ: Air conditioner efficiency factor

• K: A factor depends on total thermal mass. 

• u: Electricity consumption (same as x so far, but it is shown as u for input)

67

Page 68: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• We can show that, when it comes to cooling, we have:

• Therefore, the ECS design for the air‐conditioner will be:

• Designing a closed‐loop controller to maintain v close to its set‐point.

• The set point will be chosen by the user. 

ODtuKvv )1()1(

68

Page 69: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Residential hot water system is a major power consumer.

• Cold water enters at the bottom.

• Hot water leaves at the top.

• Heater is an electric resistor.

• Designed to avoid mix of water.

• We have n layers of water:

– Layer i: Uniform temperature Ti and volume Vi.

69

Page 70: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Two comfort settings:

• Tmax:  The maximum temperature of water in the tank.

• Tmin: The minimum temperature at which water is allowed to leave.

• Another comfort parameter is the volume of hot water available:

• At temperature Tmin.

• You should always have enough warm water to reach user’s needs. 

70

Page 71: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Mathematically, this last item can be modeled based on SoC:

• State‐of‐charge (SoC):

• The ratio of the energy content of the available water with higher than Tmintemperature, versus the energy content of a full tank reaching Tmax.

n

ii

i

n

iii

TTV

TTTTVSoC

,1minmax

min1

min

)(

),()(100

Indicatorfunction

71

Page 72: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• The third comfort parameter can be in form of SoCmin:

• ECS should make sure that the above condition always holds.

• The control variable: turning the heater ‘on’ and ‘off’.

• Q: When and for how long should we switch ‘on’ for TOU prices?

minSoCSoC

72

Page 73: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• We define:

• P : The power consumption of the heater when it is ‘on’.

• : Electricity efficiency of the heater.

• The time it takes to reach Tmax from current temperatures Ti:

• Cost of reaching this point:   

73

n

iii TTV

Pt

1maxmax )(

.186.4

max

h.hour at Pricet

th

P

Page 74: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Every time we switch on the heater:

• The heater stays on until we reach Tmax .

• The cost will depend on the time of switching on and the TOU price values.

• Due to the heat loss and usage, the temperature will gradually go down.

• ECS should decide:   

• Select the switching on cycles to minimize cost and assure                           .

74

minSoCSoC

Page 75: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Appliances may or may not be interrupted.

• In either case they may have some flexible load. 

• You can turn on and off interruptible load any time you want.

• Example: PHEV, Dryer

• You can postpone the operation for a non‐interruptible load:

• But when you start operation, you cannot stop it until the work is done.

75

Page 76: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

ECS: Handling Different Types of Load

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Some loads may be modeled using utility functions. 

• Utility value: user’s level of satisfaction about energy consumption

• Key idea: Users will benefit from consuming more. 

• Could represent industrial load: 

• More power consumed, more products will be manufactured. 

• Example:  )1log()( ha

ha xxU

76

Page 77: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

Google’s Data Center next to Columbia River in The Dalles, Oregon.  

Ref: R. H. Katz, 2009

77

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Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Google has data centers in:

• The Dalles, Oregon 

• Atlanta, Georgia

• Reston, Virginia 

• Lenoir, North Carolina 

• Goose Creek, South Carolina

• In other countries: Netherlands, Belgium, Australia, etc.

Locational Diversity (More to come soon)

78

Page 79: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Data centers are huge energy consumers.

• Take Microsoft’s data center in Quincy, WA:

• 43,600 square meters of space.

• 4.8 kilometers of chiller piping

• 965 kilometers or electric wire

• 1.5 metric tons of batteries for backup power

• Total load = 48 megawatts: enough power for 40,000 homes!

79

Page 80: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Data centers pay a lot on their electricity bills!

• Therefore, DR and ECS can significantly help data centers.

• Key question: how can we model the load in data centers?

Ref: Qureshi, 2009

Annual electricity cost at $60 / MWh

80

Page 81: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Let Pcluster be the power usage of a server cluster.

• Let n be the number of servers in the cluster.

• Let ut be its average CPU utilization (between 0 and 1) at time t:

),()( nuVnFP tcluster

Empirically DerivedCorrection Constant

Fixed Power

Variable Power

81

Page 82: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• We have:

where

– Pidle: average idle power draw of a single server

– Ppeak: average peak power draw of a single server

– r: empirically derived constant, accurate: r = 1.4, OK: 1 

)2()(),(

))1(()(rttidlepeakt

peakidle

uuPPnnuV

PPUEPnnF

82

Page 83: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• PUE: Data center power usage effectiveness.

• Some typical numbers:

– Pidle= 150 watts

– Ppeak = 250 watts

– PUE = 1.3 

• Therefore, we can model the electric load in terms of n and ut.

83

Page 84: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Similarly, the quality‐of‐service can be modeled in n and ut.

• Depending on the data center workload:

– We may turn on more / less computer clusters and servers 

– We may need to run servers at higher / lower utilization

• We can decide to serve better / more workload:

– But then it will be at the cost of higher electric bills!

84

Page 85: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Sample workload trend on Akamai (content distribution) servers:

• The workload varies over time and over different days.

• Q: How can we design an ECS unit for data centers?

85

Page 86: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• The key is to benefit from locational diversity!

• The price of electricity varies over time and over different days.

Daily averages of day‐ahead peak prices at different regions

86

Page 87: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• For most load, ECS unit diversifies load across time.

• For data centers, ECS unit also diversifies load across regions. 

• Part of ECS is placed in a task distribution server.

• More workload is forwarded to data centers:

– That face cheaper electricity in their region

– Each data center may be favored at part of day

87

Page 88: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• For data centers, ECS unit also diversifies load across regions.

• The total workload =                  .

N

ii t

1

][

88

Page 89: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• For data centers, ECS unit also diversifies load across regions.

• The power consumption Pi[t] is proportional to service rate µi[t]. 

• µi[t] ~ n ut

89

Page 90: Topic 4: Demand Responsehamed/Smart_Grid_Topic... · Topic 4: Demand Response A.H. Mohsenian‐Rad(U of T) Networking and Distributed Systems 1 Department of Electrical & Computer

Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• For data centers, ECS unit also diversifies load across regions.

• We can redistribute the workload.

• This will move the power load

– From one bus

– To another bus

• Combine with power flow analysis

• You can solve congestion problems.

90

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Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• For data centers, ECS unit also diversifies load across regions.

• Assume Bus 15 is congested.

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Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• For data centers, ECS unit also diversifies load across regions.

• Assume Bus 15 is congested.

25%

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Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• For data centers, ECS unit also diversifies load across regions.

• Assume Bus 15 is congested.

25%

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Demand Response: Data Centers

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• For data centers, ECS unit also diversifies load across regions.

• Assume Bus 15 is congested.

• We can reduce the load on Bus 15.

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Demand Response: Load Synchronization Problem

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Consider the following time‐of‐use prices:

• For an ECS, it is reasonable to shift the load from 6 PM to 3 PM.

• Q: But what if every ECS does the same? 

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Demand Response: Load Synchronization Problem

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Load Synchronization:

• Shifting away a major load from an on‐peak hour to an off‐peak hour.

• Creating a new peak load, just at a different hour!

• If demand response is manual, load synchronization is unlikely.

• However, with major ECS penetration, this is a possible problem. 

• Q: How can we avoid load synchronization? 

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Demand Response: Load Synchronization Problem

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Self‐organizing demand response:

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Key aspect: ECS units / smart meters communicate with the utility and with each other.

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Demand Response: Load Synchronization Problem

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Self‐organizing demand response:

• Users in a neighborhood make a collaborative effort:

– To minimize the energy expenditure for all participating users. 

• The ECS devices will still implement the decisions. 

• The ECS decisions are made using

– Optimization and

– Game Theory!

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Demand Response: Load Synchronization Problem

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Self‐organizing demand response:

• Instead of announcing the price values:

• Let users know about the energy cost function Ch(.) at each hour. 

• Distribute the cost fairly among users. 

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Demand Response: Coexistence Problem

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Assume we have 50% penetration of ECS units in a neighborhood

• This means that half of the users consume energy just the way they like.

• Those who participate in demand response:

• Work hard (Q: how?) to reduce the peak‐load.

• This will bring down the cost of generation and price of electricity.

• But those who did not participate will also benefit. 

• Q: Why should you participate, if you could benefit with no participation?

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Demand Response: Coexistence Problem

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Key challenge: 

• Set the prices to assure rewarding those who 

– Contribute in reducing the peak load. 

• The reward should be proportional to the user’s contribution. 

• Q: How can we measure a user’s contribution?

• Q: Do we need new pricing models? 

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Demand Response: Offering Ancillary Services

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• According to the Federal Energy Regulatory Commission:

• On average, ancillary services account for about 10% of thetotal generation and transmission costs of the power system.

Ancillary services are necessary to support thetransmission of power from sellers to buyers giventhe obligation of control areas and transmissionutilities to maintain a reliable operation of theinterconnected transmission system / grid.

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Demand Response: Offering Ancillary Services

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• Example: Regulation (Frequency Response) as Ancillary Service

• To help the grid maintain the balance between supply and demand:

• To tackle the moment‐to‐moment variations in

• Customer demand

• Scheduled generation (e.g., renewable generation)

• Q: Can demand response help in regulation?

• Q: How about we charge or discharge a group of PHEVs?

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Demand Response: Final Words

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• PJM has an interesting way to reward consumers to reduce load.

• They count your load at the five peak hours every day.

• They take the average over a year or a season.

• The number is compared with a similar number last year.

• You will get rewards if:

• You have reduced your load at peak hours compared to last year.

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References

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• K. Hamilton and N. Gulhar, “Taking Demand Response to the Next Level,” IEEE Power and Energy Magazine,  May/June 2010.

• Federal Energy Regulatory Commission, Assessment ofDemand Response and Advanced Metering, February 2011.

• N. Ruiz, I. Cobelo, and J. Oyarzabal, "A Direct Load ControlModel for Virtual Power Plant Management," IEEE Transactionson Power Systems, vol. 24, no. 2, pp. 959–966, May 2009.

• R. H. Katz, Tech Titans Building Boom, iEEE Spectrum, pp. 41‐54, February 2009.

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References

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• A. H. Mohsenian‐Rad and A.Leon‐Garcia, "Optimal ResidentialLoad Control with Price Prediction in Real‐Time ElectricityPricing Environments," IEEE Transactions on Smart Grid, vol. 1,no. 2, pp. 120–133, Sept. 2010.

• C. Wu, H. Mohsenian‐Rad, and J. Huang, “Wind PowerIntegration via Aggregator‐Consumer Coordination: A GameTheoretic Approach”, in Proc. of the IEEE PES Innovative SmartGrid Technologies Conference, Washington, DC, January 2012.

• A. Qureshi, R. Weber, H. Balakrishnan, J. Guttag, and B. Maggs,"Cutting the Electric Bill for Internet‐Scale Systems," in Proc. onACM SIGCOMM, Barcelona, Spain, Aug 2009.

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References

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• P. Samadi, H. Mohsenian‐Rad, R. Schober, and V. Wong,"Demand Side Management for Smart Grid: Opportunities andChallenges," accepted as a book chapter in Smart GridCommunications and Networking, Edited by Vincent Poor, ZhuHan, and Ekram Hossain, Cambridge University Press, 2011..

• C. Wu, H. Mohsenian‐Rad, J. Huang, "Vehicle‐to‐Grid Systems:Ancillary Services and Communications," accepted as a bookchapter in Smart Grid Communications and Networking, Editedby Vincent Poor, Zhu Han, and Ekram Hossain, CambridgeUniversity Press, 2011.

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References

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• K. Vanthournout and R. D'hulst and D. Geysen and G. Jacobs,"A Smart Domestic Hot Water Buffer", IEEE Transactions onSmart Grid, Special Issue: Intelligent Buildings and Home EnergyManagement in a Smart Grid Environment, 2012.

•A. H. Mohsenian‐Rad, V.Wong, J.Jatskevich, R.Schober, andA.Leon‐Garcia, "Autonomous Demand Side Management Basedon Game‐Theoretic Energy Consumption Scheduling for theFuture Smart Grid," IEEE Transactions on Smart Grid, vol. 1, no.3, pp. 320–331, Dec. 2010.

•H. Mohsenian‐Rad and A. Leon‐Garcia, "Coordination of CloudComputing and Smart Power Grids," in Proc. of IEEE Smart GridCommunications Conference, Gaithersburg, MD, October 2010.

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References

Dr. Hamed Mohsenian-Rad Texas Tech UniversityCommunications and Control in Smart Grid

• H. Mohsenian‐Rad, V.Wong, J.Jatskevich, R.Schober, "Optimaland Autonomous Incentive‐based Energy ConsumptionScheduling Algorithm for Smart Grid," in Proc. of IEEE PESConference on Innovative Smart Grid Technologies, MD, 2010.

• M. Ghamkhari and H. Mohsenian‐Rad, "Optimal Integration ofRenewable Energy Resources in Data Centers with Behind‐the‐Meter Renewable Generator", in Proc. of the IEEE InternationalConference in Communications, Ottawa, Canada, June 2012.

• C. Wu, H. Mohsenian‐Rad, J. Huang, "Vehicle‐to‐AggregatorInteraction Game”, IEEE Trans. on Smart Grid, Special Issue onTransportation Electrification & Vehicle‐to‐Grid App., 2012.

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