Optimizing Power System Optimizing Power System Restoration Resources and Restoration Resources and Actions Actions Chen Chen - - Ching Liu Ching Liu Electrical and Computer Engineering Electrical and Computer Engineering Iowa State University Iowa State University PSERC Research Tele-seminar, November 2006
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Optimizing Power System Optimizing Power System Restoration Resources and Restoration Resources and
Actions Actions
ChenChen--Ching LiuChing LiuElectrical and Computer EngineeringElectrical and Computer Engineering
Iowa State UniversityIowa State University
PSERC Research Tele-seminar, November 2006
2
State of the Art
•• Primarily manual work by Primarily manual work by operatorsoperators
•• Off line restoration planningOff line restoration planning•• Little progress has been made on Little progress has been made on
system restoration methodology system restoration methodology •• On line implementation limitedOn line implementation limited•• Literature Literature
3
System Restoration Stages
Load restoration is only a means to an end
Load restoration is the objective
PREPARATIONActions are time-critical
SYSTEMRESTORATION
LOAD RESTORATION
30-60 minutes
3-4 hours
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System Restoration Tasks
•• Knowing status of the grid Knowing status of the grid •• Maximizing generation capabilities Maximizing generation capabilities
with the available black start resourceswith the available black start resources•• Scheduling of tasks and resources during Scheduling of tasks and resources during
system restorationsystem restoration•• Establishing transmission capability Establishing transmission capability
and paths while meeting operating and paths while meeting operating constraintsconstraints
•• Picking up load while meeting Picking up load while meeting operating constraints and load operating constraints and load requirementsrequirements
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Example Restoration Strategies
•• BuildBuild--upwardupward•• BuildBuild--downwarddownward•• Other variationsOther variations
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First Stage
•• Basic operations common to all Basic operations common to all strategiesstrategies
•• SubSub--processes defining early processes defining early stages of restoration processstages of restoration process
•• Minimal configuration of Minimal configuration of autonomous stable source with autonomous stable source with necessary transmissionnecessary transmission
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Restoration Building Blocks
•• May include nonMay include non--autonomous autonomous BTG, connection transmission, BTG, connection transmission, necessary compensation & load necessary compensation & load blocksblocks
•• Associated with schedule of Associated with schedule of switching & control actionsswitching & control actions
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Second StageTarget System
•• System state achieved by end of System state achieved by end of restoration processrestoration process
•• May not be preMay not be pre--disturbance disturbance systemsystem
•• Restrict set of postRestrict set of post--restoration restoration configurationsconfigurations
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Restoration Constraints
•• Physical constraintsPhysical constraints•• Scheduling constraintsScheduling constraints•• Policy constraintsPolicy constraints
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Third Stage
Load Restoration Load Restoration –– Pick Up LoadsPick Up Loads
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BLACK-START UNIT OPERATION
NON-BLACK-START UNIT OPERATION
STATICMVAR
INSPECTION
STABILITYINSPECTION
SWITCHINGSEQUENCE INSPECTION
TRANSIENTVOLTAGEINSPECTION
CAPACITYINSPECTION
FAULTINSPECTION
MAN-POWER DISPATCH
FUEL INSPECTION
MECHANICAL INSPECTION
SYSTEM RESTORATION
LOAD MANAGEMENT
MW MANAGEMENT
MVAR MANAGEMENT
PATH MANAGEMENT
Restoration Strategy
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Example – Generation Capabilities
(4 Different Generating Units)(4 Different Generating Units)
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Example – Optimal Starting Sequence
MW
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Cranking Priorities
•• Units with critical maximum Units with critical maximum intervalinterval
•• Critical max interval units with Critical max interval units with most urgent time constraint most urgent time constraint
•• Units that can generate highest Units that can generate highest MWH within a given period MWH within a given period
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Unit Type MW Cap. Ramp. rate Crank to paral. Crit. max. int. Crit. min. int. Startup req.(MW) (MW/hr) (hr) (hr) (hr) (MW)
Chester_4 CT 15 40 0 N/A N/A 0Chester_5 CT 15 40 0 N/A N/A 0Chester_6 CT 15 40 0 N/A N/A 0Chester_7-9 CT 45 120 0 N/A N/A 0Conowingo_1-7 Hydro 200 200 0 N/A N/A 0Conowingo_8-11 Hydro 200 200 0 N/A N/A 0Cromby_1 Steam 180 80 1:40 N/A N/A 8Cromby_2 Steam 180 80 1:40 N/A N/A 8Croydon_1 CT 300 120 0:30 N/A 5:00 6Delaware_7 Steam 130 60 2:40 3:20 N/A 5Delaware_8 Steam 130 60 2:40 3:20 N/A 5Delaware_9-10 CT 30 90 0 N/A N/A 0Delaware_11-12 CT 30 90 0 N/A N/A 0Eddystone_1 Steam 150 40 1:40 N/A 3:20 12Eddystone_2 Steam 150 40 1:40 N/A 3:20 12Eddystone_3 Steam 150 40 1:40 N/A 3:20 12Eddystone_4 Steam 150 40 1:40 N/A 3:20 12Eddystone_10 CT 15 45 0 N/A N/A 0Eddystone_20 CT 15 45 0 N/A N/A 0Eddystone_30-40 CT 30 90 0 N/A N/A 0Falls_1-3 CT 45 135 0 N/A N/A 0Moser_1 CT 30 90 0 N/A N/A 0Muddy Run_1-4 Hydro 400 150 0:30 N/A N/A 6.6Muddy Run_5-8 Hydro 400 150 0:30 N/A N/A 6.6Richmond_3 CT 50 100 0 N/A N/A 0Richmond_4 CT 50 100 0 N/A N/A 0Schuylkill_1 Steam 135 135 2:00 2:30 N/A 2.7Schuylkill_3 Steam 135 135 2:00 2:30 N/A 2.7S h lkill 10 CT 15 45 0 N/A N/A 0
. . . . . .
Ramping Rate Ramping Rate
Critical Min. Interval Critical Min. Interval
Critical Max. IntervalCritical Max. Interval
PECO-Energy Generating Units
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MW Capability Curves
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TIE LINEUTILIZATION
BLACK-START UNIT OPERATION
NON-BLACK-START UNIT OPERATION
STATICMVAR
INSPECTION
STABILITYINSPECTION
SWITCHINGSEQUENCE INSPECTION
TRANSIENTVOLTAGEINSPECTION
CAPACITYINSPECTION
FAULTINSPECTION
MAN-POWER DISPATCH
FUEL INSPECTION
MECHANICAL INSPECTION
SYSTEM RESTORATION
LOAD MANAGEMENT
MW MANAGEMENT
MVAR MANAGEMENT
PATH MANAGEMENT
TIE LINEUTILIZATION
Restoration Strategy with Tie Lines
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Check If There Is a Path Between Them
System Restoration
LoadManagement
Tie LineUtilization
MWManagement
Check If a Tie Line Can Crank an NBS Unit
Check If Tie Line Can Provide Enough Cranking Power
Negotiate for More Power Import
Check If Enough Load Can Be Found
Negotiate for Less Power Import
PathManagement
Crank NBS Units
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Check If System Can Provide Enough Power
System Restoration
LoadManagement
Tie LineUtilization
MWManagement
Respond to Tie Line Request
Decide Priorityof Tie Line
CheckLoad RestorationCondition
Check NBS UnitsRestartCondition
PathManagement
Negotiate for Less Power Export
Check Trans-mission Capacity
MVARManagement
Respond to Request
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Check ifThere AreTrans-missionPaths
System Restoration
LoadManagement
Tie LineUtilization
MWManagement
Check if a Tie Line Can Serve Loads
Check ifTie LineCanProvideEnoughPower
Check ifEnoughLoadCan BeFound
PathManagement
MVARManagement
Negotiatefor MorepowerImport
Consider UsingTie LineInstead of SystemGeneration
Negotiatefor LessPowerImport
Serve Load
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S1
TLi
TLe
Internal Unitsto be Cranked by TLi
22
S2
TLi
TLe
Internal Unitsto Provide TLe - TLi
23
CT
TLi
TLe
S3
Cranking Paths Affected
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G1
G2
G3
Induced MWh Increase
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MWh Increase by S1Increase from Earlier Startup of S1Increase Induced by S1
MWh Decrease by S2 (S3)Decrease from Delayed Startup of S2 (S3)
Decrease Induced by S2 (S3)
Tie Line Utilization
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5678 1234MUDDY RUN
PEACH BOTTOM
CONOWINGO124567 8 9 10 113
CROMBY
Test Subsystem
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Min after blackout
0
500
1000
1500
2000
2500
3000
3500
0 100 200 300 400 500 600
Without PeachBottom
With PeachBottom
System Generation Capability
MW
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Min after blackout
MW
0
500
1000
1500
2000
2500
3000
3500
0 100 200 300 400 500 600
0MW
10MW
50MW & 100MW
System Generation Capability
From Peach Bottom
MW
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Generic Restoration Actions (GRAs)
•• start_black_start_unit (X)start_black_start_unit (X)•• find_path (X,Y)find_path (X,Y)•• energize_line (X)energize_line (X)•• pick_up_load (X)pick_up_load (X)•• synchronize (X,Y)synchronize (X,Y)•• connect_tie_line (X)connect_tie_line (X)•• crank_unit (X)crank_unit (X)•• energize_busbarenergize_busbar (X)(X)
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Using GRAs to Construct RBBs
NBSBS
B1B2
B3
L1 L2C1
C2
C3
S1
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Using GRAs to Construct RBBs
•• Find transmission path between Find transmission path between BS & NBSBS & NBS
•• Start blackStart black--start unit BSstart unit BS•• Build transmission path from Build transmission path from
busbarbusbar B1 to B3 and pick up loads B1 to B3 and pick up loads for stabilizationfor stabilization
•• Crank nonCrank non--blackblack--start unit NBSstart unit NBS
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Using RBBs & GRAs to Build Restoration
Strategies
NBS
BS1
B1
B2B3
L1
L2
L3C1a
C2a C3
BS2
C1b
C2b
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Using RBBs & GRAs to Build Restoration
Strategies•• Select Two Select Two RBBsRBBs
–– RBB1: Use BS1 to energize B1RBB1: Use BS1 to energize B1–– RBB2: Use BS2 to energize B2RBB2: Use BS2 to energize B2
•• Build RBB1Build RBB1–– Prepare loadPrepare load–– Start BS unitStart BS unit–– Energize busEnergize bus
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Using RBBs & GRAs to Build Restoration Strategies (Cont.)
•• Build RBB2Build RBB2•• Energize ringEnergize ring•• Restart nonRestart non--blackblack--start unit NBSstart unit NBS•• Pick up loads along ringPick up loads along ring
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Petri Net Algorithm to Optimize Sequence of GRAs
TL1
Bus2
Bus1
Bus3
L1
L2 L3
Line1-2
Line2-3
Line3-1
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Petri Net Model
P1 P2
P8
T1
T2
P15
T15
P16
P22
P25
T14
P14 P3 P9 P4
T3T4 T5
P17
T16
P21
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Schulykill-SouthwarkSubsystem
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Time to Complete GRAs
1010Pick up LoadPick up Load
2020Synchronize between Synchronize between BusbarsBusbars/Lines/Lines
1515Crank a NBSUCrank a NBSU2525Connect Tie LineConnect Tie Line
55Energize Energize BusbarBusbar from from BSU/BSU/busbarbusbar/line/line
1515Restart BSURestart BSU
Time (Time (minsmins.).)Generic Restoration Generic Restoration Action (GRA)Action (GRA)
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Sequence of Actions for Schuylkill-Southwark
============================================================Time (min.) ActionsTime (min.) Actions----------------------------------------------------------------------------------------------------------Restoration Building Block 1:Restoration Building Block 1:
0 Connect BSU CT100 Connect BSU CT1015 Energize bs2 from CT1015 Energize bs2 from CT1020 Energize bs3 from bs220 Energize bs3 from bs225 Energize bs4 from bs325 Energize bs4 from bs330 Crank NBSU ST3 from bs430 Crank NBSU ST3 from bs445 Synchronize ST3 with bs445 Synchronize ST3 with bs4----------------------------------------------------------------------------------------------------------
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Sequence of Actions for Schuylkill-Southwark
============================================================Time (min.) ActionsTime (min.) Actions----------------------------------------------------------------------------------------------------------Restoration Building Block 2:Restoration Building Block 2:
0 Connect BSU CT30 Connect BSU CT3--4415 Energize bs9 from CT315 Energize bs9 from CT3--4420 Energize bs10 from bs920 Energize bs10 from bs925 Energize bs11 from bs1025 Energize bs11 from bs1030 Crank NBSU ST1 from bs1130 Crank NBSU ST1 from bs1145 Synchronize ST1 with bs1145 Synchronize ST1 with bs11
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Sequence of Actions for Schuylkill-Southwark
----------------------------------------------------------------------------------------------65 Energize bs1 from bs2, bs14 from bs2, bs12 from65 Energize bs1 from bs2, bs14 from bs2, bs12 from
bs3, bs5 from bs4, bs30 from bs9, bs8 from bs9, bs3, bs5 from bs4, bs30 from bs9, bs8 from bs9, bs17 from bs11, bs15 from bs11, bs25 from bs10bs17 from bs11, bs15 from bs11, bs25 from bs10
70 Energize bs22 from bs1, bs19 from bs14, bs13 from bs170 Energize bs22 from bs1, bs19 from bs14, bs13 from bs12, bs72, bs7from bs5, bs31 from bs39, bs21 from bs25, and synchfrom bs5, bs31 from bs39, bs21 from bs25, and synchronize ronize bs14 with bs15bs14 with bs15
75 Energize bs32 from bs31, bs20 from bs21, bs23 from bs75 Energize bs32 from bs31, bs20 from bs21, bs23 from bs22, 22, and connect bs7 with bs13, bs8 with bs7, and bs22 wand connect bs7 with bs13, bs8 with bs7, and bs22 with bs21ith bs21
80 Energize bs24 from bs23, bs26 from bs2080 Energize bs24 from bs23, bs26 from bs2085 Energize bs27 from bs2685 Energize bs27 from bs2690 Energize bs28 from bs2790 Energize bs28 from bs27----------------------------------------------------------------------------------------------------------
42
Further Information
•• M. M. M. M. AdibiAdibi (Ed), (Ed), Power System Restoration Methodologies Power System Restoration Methodologies & Implementation Strategies& Implementation Strategies, IEEE Press, 2000., IEEE Press, 2000.
•• J. Wu, C. C. Liu, and R. Chu, J. Wu, C. C. Liu, and R. Chu, ““A Petri Net Algorithm for A Petri Net Algorithm for Scheduling of Generic Restoration Actions,Scheduling of Generic Restoration Actions,”” IEEE Trans. IEEE Trans. Power SystemsPower Systems, Feb. 1997, pp. 69, Feb. 1997, pp. 69--76.76.
•• L. Fink, K. L. L. Fink, K. L. LiouLiou, and C. C. Liu, , and C. C. Liu, ““From Generic From Generic Restoration Actions to Specific Restoration Strategies,Restoration Actions to Specific Restoration Strategies,””IEEE Trans. Power SystemsIEEE Trans. Power Systems, May 1995, pp. 745, May 1995, pp. 745--752.752.
•• K. L. K. L. LiouLiou, C. C. Liu, and R. Chu, , C. C. Liu, and R. Chu, ““Tie Line Utilization Tie Line Utilization during Power System Restoration,during Power System Restoration,”” IEEE Trans. Power IEEE Trans. Power SystemsSystems, Feb. 1995, pp. 192, Feb. 1995, pp. 192--199.199.
•• C. C. Liu, K. L. C. C. Liu, K. L. LiouLiou, et al., , et al., ““Generation Capability Generation Capability Dispatch for Bulk Power System Restoration Dispatch for Bulk Power System Restoration –– A A KnowledgeKnowledge--Based Approach,Based Approach,”” IEEE Trans. Power IEEE Trans. Power SystemsSystems, Feb. 1993, pp. 316, Feb. 1993, pp. 316--325. 325.
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