DEMAND-BASED FREQUENCY CONTROL (DBFC)

Jason W Black, Marija Ilic

MIT

March 15, 2002

Intro to DBFC

• Loads Respond to Frequency deviations

• Decentralized control – similar to AGC

• Utilizes energy based (e.g. Water Heaters, AC) rather than power based (e.g. lights, Televisions) loads

Motivation

• Islanding/Mini-Grids– Growth in DG– Replacement of T&D investments by DG

• Issues with Renewable DG– Uncontrollable and uncertain Power Production

• Necessitates additional AGC and Reserves

Appliance/Use Percent of Consumption

Hot Water 25

Heat 23

Refrigeration 10

Freezer 4

Demand Side Potential

Energy dependent Loads (Residential):

* From ELCAP Study in Pacific Northwest

Control Scheme

imbCL

devG

control PPPP

maxminimbimbimb PPP

minmin LGimbP maxmax LGimbP

max

1/

LG

n

iLiiS PpT

Control Needed:

Where:

And

Sampling Time:

Single Control Characteristic

fact

P

AGC

f

-fact

Aggregate Control Characteristic

TS

PL

t

P

max LGSlope =

Simulations

DG

SystemPSYS = 6 MW

PL = 10 MW

PDG = 4 MW

DG

System

DG

SystemPSYS = 6 MW

PL = 10 MW

PDG = 4 MW

PL = 10 MW

PWIND = 10 MW

PL = 10 MW

PWIND = 10 MW

Islanded System Mini-Grid

Simulation Assumptions

• Asynchronous Wind Generator with random deviations

• Sequence of Equilibria - No Transient stability Issues

• 20% of Load Participation

• 5 minute activation time of controls

Simulation Results

0 100 200 300 400 500 600 700 800 900 1000-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25Uncontrolled

Controlled

Fre

qu

ency

Dev

iati

on (

Hz)

Time (s)

Fre

qu

ency

Dev

iati

on (

Hz)

0 100 200 300 400 500 600 700 800 900 1000-4

-2

0

2

4

6

8x 10

-3

Uncontrolled

Controlled

Time (s)

Islanded System Mini-Grid

Conclusions

• DBFC can alleviate DG issues such as:– Islanding– Reserve Requirements– Lack of Controllability of renewables

• DBFC can augment AGC

• Potential for competitive bidding for AGC or reserves

Issues

• Costs of Implementation– Metering accuracy– Native (appliance level) vs Local Response

(building level)

• Droop Characteristics– Unknown for load and generation

• Willingness to Participate and level of participation needed

References

1. Black, Jason W., Ilic, Marija, “Survey Of Technologies And Cost Estimates For Residential Electricity Services”, Proceedings IEEE Power Engineering Society Summer Meeting, Vancouver, Canada, July 2001.

2. Constantopoulos, P., Schweppe, F., and Larson, R., “ESTIA: A Real-Time Consumer Control Scheme for Space Conditioning Usage Under Spot Electricity Pricing”, Computers Operations Research, Vol. 18, No 8, pp 751-765, 1991.

3. Haykin, S., Communication Systems, Wiley and Sons, 1983.4. Ilic, M., Skantze, P., Yu, C-N., Fink, L.H., Cardell, J., "Power Exchange for Frequency Control

(PXFC)", Proceedings of the International Symposium on Bulk Power Systems Dynamics and Control-IV: Restructuring, Santorini, Greece, August 23-28, 1998.

5. Ilic, M.D. and J. Zaborszky, Dynamics and Control of Large Electric Power Systems, Wiley Interscience, May 2000.

6. Pratt, R. G., C. C. Conner, E. E. Richman, K. G. Ritland, W. F. Sandusky, M. E. Taylor. “Description of Electric Energy Use in Single Family Residences in the Pacific Northwest”, DOE/BP-13795-21, Bonneville Power Administration, Portland, Oregon, 1989.

7. Ilic, M. “Model-based Protocols for the Changing Electric Power Industry”, Proceedings of the Power Systems Computing Conference (PSCC), Spain, July 2002. (Under Review).

8. Schweppe, F., et al., “Homeostatic Utility Control”, IEEE Transactions on Power Apparatus and Systems, Vol. PAS-99, No. 3, May/June 1980.