Power System Economics and arket odeling 8: Developing an LP nalysis for a Large Case 2001 South First Street Champaign, Illinois 61820 +1 (217) 384.6330 support@powerworld.com http://www.powerworld.com
LP nalysis: Outline Sample PJ study: process overview One possible step by step approach for developing LP nalysis on a large case Use of Super rea to model ISO control Unenforceable constraints ore on unenforceable constraints and other OPF challenges 8: LP Large System 2
Sample PJ Study 8: LP Large System 3
Process Overview Case Development Select area(s) of interest for study Establish the set of OPF controls: OPF, unit commitment, and GC settings Establish the set of OPF constraints: Limit onitoring settings Load cost curves for thermal generators Solve unconstrained OPF for area lambdas Set hydro dispatch to historical levels and hydro cost curves to unconstrained area lambdas Solve OPF Review results, analyze unenforceable constraints, and iterate process as necessary 8: LP Large System 4
Case Development Suggestions Full OPF analysis on a large case may be time consuming For extremely congested cases, there may be no solution that satisfies all constraints For meaningful results, it is recommended that the scope of analysis be limited to a region of interest such as a few control areas or a single RTO territory 8: LP Large System 5
Case Development Suggestions lign the part of the system to be optimized with the generator controls to remove the constraints Do not monitor elements in the part of the system not on OPF control Only place the part of the system to be studied on OPF control 8: LP Large System 6
Eastern.pwb Eastern Interconnect Case Load the Eastern.pwb case 3964 total generating units 143 branch thermal violations in base case Suppose we wish to model an LP market for the Eastern portion of the PJ Interconnect 11 separate control areas 593 total generating units, 407 committed generating units 37 branch thermal violations in base case 8: LP Large System 7
Starting Case with Overloads on High Voltage Grid Note use of Emphasis, Dynamic Formatting, and dynamicallysized pie charts on one line diagram 8: LP Large System 8
Case Development rea/zone Filters: show areas 25 35 only OPF Controls Set areas 25 35 on OPF control Set GC to YES for all generators in areas 25 35 except hydro (settings stored in cost curve aux file) Limit onitoring Settings Report limits for areas 25 35 only, 100 kv and above Do not monitor radial lines 8: LP Large System 9
Limit onitoring 8: LP Large System 10
Cost Curves Load cost curves for thermal units: stored in aux file 08_LP Large System\EasternCostCurvePJ.aux 8: LP Large System 11
Solve Unconstrained OPF Do not enforce branch or interface constraints 8: LP Large System 12
Set Cost Curves for Hydro Units For each Hydro Unit (advanced filter Hydro PJ) Set offer price (Wh Price 1) equal to W arginal Cost of its bus Set GC = YES 8: LP Large System 13
Solve Constrained OPF Enable constraint enforcement (on Constraint Options) Solve OPF, note several unenforceable constraints 8: LP Large System 14
LP Contour Note high LPs on receiving end of constrained lines and areas with low reserve margin 8: LP Large System 15
Effect of Line Constraints ROXBURY Bus: ROXBURY (221) Nom kv: 115.00 rea: PENELEC (26) Zone: PN 115KV (5) 0.99 pu 114.17 KV 22.42 Deg 329.56 $/Wh 109.3 W -26.9 var 112.6 V 15.9 W 10.1 var 18.8 V 0.0 W 0.0 var ID 1 112.0 W 18.7 var 113.6 V 18.6 W -1.9 var 18.7 V 0.00 W 0.00 var 87% 0.9780 tap V CKT 1 ROXBURY etc 233 mps 99% 86% 0.9790 tap LP 01GRNDP 20187 0.98 pu 135.84 KV P 0.00 $/Wh Note difference in LP on each end of constrained line CKT 1 CRLISLE 205 0.99 pu 113.87 KV 275.59 $/Wh mps CKT 1 SHDE GP 223 1.01 pu 116.61 KV -448.11 $/Wh V CKT 1 ROXB SUB 256 CRL PKE 260 CRLISLE 205 0.99 pu 113.87 KV 275.59 $/Wh 8: LP Large System 16
Options for Further nalysis Increase available units (and reserve margin) in areas with limited supply any generators at their max output Only 4.4% operating reserves competitive market would likely have more units committed more controls Place PJ reas on Super rea Control 8: LP Large System 17
Unit Commitment and Reserves ost generators in high LP area DP&L on Delmarva Peninsula are at max 8: LP Large System 18
PJ Super rea Hydro Price = $57 8: LP Large System 19
Options for Further nalysis Check sensitivities on unenforceable constraints Optionally ignore or raise limits, change unit commitment, or include demand response (curtailable load) Some unenforceable constraints may be unavoidable due to load pockets Incorporate contingencies with Contingent Interfaces (flowgates) Change cost curves (e.g. model a 10% increase in fuel cost) 8: LP Large System 20
Unenforceable Constraints Examine LP Basis atrix Run multiple element TLR on overloaded lines to understand relationship between flows and generator and load values 8: LP Large System 21
LP Basis atrix arginal controller sensitivities have very low absolute value suggests presence of load pockets The sensitivity vector of each control has a mix of signs adjusting the control to relieve one constraint makes another worse 8: LP Large System 22
ultiple Element TLR TLR on overloaded lines with Super rea as buyer Negative values on decommitted generators indicate units that may relieve congestion if committed Positive values on committed generators (especially those at in W) indicate that de committing may help 8: LP Large System 23
ultiple Element TLR dd ETLR field to generator display and sort Note how committed units with most negative ETLR are generally maxed out Try committing more units with negative ETLR or those with highest product of ETLR and ax W (custom expression TLR Potential ) Solve power flow, then Resolve OPF 8: LP Large System 24
Demand Response Loads may have benefit functions, allowing them to respond to price signals in the OPF Load the aux file EasternLoadBenefitodels.aux: includes benefit functions for 156 loads that impact unenforceable constraints Enable load controls in OPF Options and Results and re solve OPF 8: LP Large System 25
Demand Response OPF Load Records display or Difference Flows may be used to identify curtailed loads and marginal benefit Unenforceable constraints due to load pockets are relieved 8: LP Large System 26
Price Contour with Demand Response 8: LP Large System 27
Incorporate Contingencies with Flowgates Load EasternContingentInterfaces.aux Each flowgate interface includes a monitored element and a contingent element ake sure Contingent Interface Elements are Enforced in OPF (Simulator Options > General tab or OPF > Interfaces Display) Re solve OPF 8: LP Large System 28
ore on OPF Challenges 8: LP Large System 29
OPF Formulation and Solution ore on Unenforceable Constraints Radial Elements var loops in C power flow Unusual modeling parameters Insufficient Reserves: not enough controls to satisfy area CE constraint Too uch Power Transfer 8: LP Large System 30
Eastern2.pwb nalysis of Unenforceable Constraints Example: Load Eastern2.pwb (has cost info) Choose dd Ons ribbon tab Primal LP We end up with 46 unenforceable constraints Of these many seem to be caused by radial Change Limit onitoring Settings to Ignore Radial Lines and Buses Radial Bus is connected to the system by only one transmission line Radial Line is a line connected to a radial bus. Choosing this reduces the unenforceable list to 30 constraints. 8: LP Large System 31
Unenforceable Constraints If you look at the W and Var flows on these lines you ll find that many have VERY large Var flows dd Columns for ax W and ax Var on dd Ons ribbon tab OPF Case Info OPF Lines and Transformers If you look through the case, you ll find many very strange LTC tap ratio settings lso some are due to phase shifters being in series with an overloaded branch 8: LP Large System 32
Reset LTC Taps Set all transformers on LTC control to a tap ratio of 1.00 UX File: 08_LP Large System\Eastern2ChangeTransformers.aux Re solve power flow, then OPF ay also examine Circulating var Flows Tools > Connections > Find Circulating W or var Flows Check relative tap ratios in Flow Cycles with high Loss var Reduction 8: LP Large System 33
Unenforceable Constraints This results in a reduced list of 20 unenforceable constraints 8: LP Large System 34
Phase Shifting Transformers Phase Shifters have three control options None leave at a fixed angle Power Flow llow the power flow solution to dispatch according to the W setpoints of the controller OPF llow the OPF s linear program to dispatch the transformer for a more global optimization OPF phase shifter control is often necessary if load is varied with the time step simulation, unless appropriate phase shifter control settings are known for each load level 8: LP Large System 35
Use Caution with Phase Shifter OPF Control Phase shifter setpoints are often important for stability The setpoints may vary with load or seasonal generation pattern Options to consider: ignore V/mp limit enforcement where obvious conflicts occur between limit and phase shifter setpoints (e.g. overloaded line in series with phase shifter) allow only a few phase shifters to operate on OPF control where it is known that stability margins are sufficient choose to Enforce W Regulation Limits in OPF (branch field for phase shifters) tighten the angle limits of phase shifters to limit range of OPF dispatch 8: LP Large System 36
Conflict between Phase Shifter Setpoint and Line Limits WP PH.S1 Bus: WP PH.S1 (6372) Nom kv: 34.50 rea: BGE (32) Zone: 32 (32) 1.01 pu 34.80 KV -43.78 Deg -2293.83 $/Wh Phase shifter setpoint is 60.3 72.9 W, but line limits are <=45 V; ignore these lines Limts 8: LP Large System 161% V 64.8 W 11.9 var 65.9 V 41.00 V CKT 1 GOULDST 6361 1.00 pu 33.94 KV NEWGT871 6287 NEWGT872 6288 WP PH.S2 6373 GOULDST 5906 GOULDST 6596 GOULDST 6599 1.0000 tap 146% V 64.8 W -11.9 var 65.9 V 45.00 V CKT 1 WESTPORT 6362 1.01 pu 13.96 KV WSPT521 6045 WSPT525 6177 WESTPORT 6367 1.0000 tap 0.00 W 0.00 var 37
Closer Look Look more closely at the majority of the remaining unenforceable constraints Continues to show a large number of under radial elements which should probably just be ignored handful of elements require greater study Draw a oneline diagram to represent this part of the system You will start to see what the problem is Changes described in following slides may be automatically loaded with 08_LP Large System\Eastern2onitor Changes.aux 8: LP Large System 38
Example: Internal Shawville 13.10 var 360 P-BURG 2-142.60 $/Wh 0.99 pu 265 0.0 W P-BURG 1 0.0 var -146.43 $/Wh 0.95 pu V 373 0.0 var 425 PHILIPSB -146.43 $/Wh 0.97 pu 436 SHWVILL -61.14 $/Wh 0.98 pu 0.98 pu -7285.82 $/Wh V 0.97 pu 434 V SHWVILL 435 SHWVILL V -17008.59 $/Wh 0.96 pu SHWVILL -17075.95 $/Wh 1.05 pu V 178.42 $/Wh 228 0.96 pu TYRONEN 0.0 W 0.0 var V 18.7 W V 7.5 var 99% V 368 SHWVILL -71.26 $/Wh 1.04 pu 151% 101% 15.1 W -13.0 var V V V V 50.2 W 21.0 var V -26.95 $/Wh 426 0.98 pu DER 15.1 W 8.3 var 257 SHWVILL -65.73 $/Wh V 0.99 pu 431 SHWVILL V -5002.14 $/Wh 0.94 pu V V 98% 17.5 W 0.0 var 15.6 W 8.5 var 152% 100% V 419 SHWVILL -17055.17 $/Wh 1.01 pu 423 SHWVILL -61.44 $/Wh 428 SHWVILL -7263.56 $/Wh 1.00 pu 372 SHWVILL -16997.95 $/Wh 1.08 pu V V -32.64 $/Wh 0.97 pu V V V V -50.38 $/Wh V 422 0.98 pu ROCKTON 50.1 W 17.1 var 424 SHWVILL 235 DER 0.3 W 0.0 var -5032.14 $/Wh 0.96 pu 15.43 $/Wh 1.00 pu V -53.10 $/Wh 0.97 pu 465 WESTOVER -33.74 $/Wh 0.98 pu 300 ROCK T 421 DUBOIS Rest of the System Four of the stepup transformers experience high loadings. We could choose to ignore these limits. The lines from 426-228 and 423-426 also experience high loadings because the generators are all at their low limits and can not back down far enought to remove these problems. We could turn off generators at buses 431 and 424 to fix this. 8: LP Large System 4.2 W 5.5 var 126.0 W 20.3 var 119.7 W -9.1 var 39
V V V V V V V V V V V V Example: Internal erck 59.29 $/Wh 1.0131 pu 4212 NWLES 82.2 W 25.2 var 82.2 W 14.1 var 23.2 W 9.0 var 90.5 var 99% V 4217 N WLES4 59.64 $/Wh 1.0185 pu 4216 NWLES 59.63 $/Wh 1.0186 pu 82.2 W 25.2 var 20.9 var 4214 NWLES 59.63 $/Wh 1.0186 pu 113% V 4215 NWLES 59.63 $/Wh 1.0186 pu 4217-4216 line has a large impedance of 0.15 compared to the lines 4214-4217, 4214-4215, 4216-4215 which have impedances of 0.0002 4153 59.63 $/Wh L 10700 1.0184 pu 59.64 $/Wh 1.0181 pu 3.9 W 1.6 var 4195 ERCK 59.63 $/Wh 1.0184 pu 4154 L 16000 This means that 4216-4217 will NEVER have any flow on it. Thus the line 4214-4217 is essentially radial. 8: LP Large System 4196 4544 ERCK ERCK 3 59.64 $/Wh 59.62 $/Wh 1.0283 pu 1.0149 pu 0.0 W 0.0 var 1.4 W -1.5 var 40
Siegfried Nazareth Limits Wh 3061 EPLERT V 463.58 $/Wh 3081 1.01 pu SIEGFRIE V V 42.2 1.03 81% V V V 3151.26 $/Wh 3391 0.98 pu KEY C 2 pu V V 18.37 var $/Wh 3376 EPLERT 59.7 59.7 W W -0.1-0.1 var var V 3195 RROWHE 1202.26 $/Wh 8: LP Large System 3403 V 1.01 pu PL T1 11.02 var V V 729.78 $/Wh 3394 7.33 var 1.01 pu ECKESVI V V V 11.02 var 1.70 var 56733$/Wh V 9.63 var 3412 3404 V 2858.32 $/Wh 0.96 pu PL T2 1211.81 $/Wh 1.01 pu 28.96 var 64.0 W 24.3 var 64.0 W 24.3 var 64.0 W 24.3 var 3408 SIEGFRIE -2645.85 V $/Wh 3390 71.3 W 10.8 var 0.98 pu KEY C 1 64.0 W 24.3 var 99% Removing the negative loads at NZRETH and an equivalent amount of positive load at SIEGFRIE relieves the otherwise difficult overloads on the branches between them. V 106% V -32 W 99% V 21.61 var -32 W 3399-4437.97 $/Wh 3415-5347.63 $/Wh NZRETH 1.03 pu CH HL 99% V V -3157.48 $/Wh -5219.33 $/Wh 3375-3403.1 1.04 p 1.03 pu CH HL T1-3157.48 $/Wh 3392 1.03 pu LSTR T1 3393 1.03 pu LSTR T2 V V V V V -4410.75 $/W 1.03 pu V -3067.50 $/ 1.03 pu 41
fter these changes we remove all unenforceable Constraints Still some very high cost constraints remain BIRDBORO PINE LNE = $753/Vhr 8: LP Large System 42
V V 18.80 var V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V V Birdboro Pine Lane Yellow Region forms a load pocket for two large loads 85.3 W 193.7 W The 69 kv lines feeding this region have high loadings 8: LP Large System 64.53 $/Wh 15.47 $/Wh 1.06 pu 1156 NBOYERTO 1590 NBOYERTO 207.74 $/Wh 1731 32.3 W TITUS 0.0 var 16.24 $/Wh 35.9 W 16.33 $/Wh 0.0 var 15.59 $/Wh 1732 1.06 pu TITUS 15.59 $/Wh 1611 W.BOYTWN -81.03 $/Wh 1582 LORNE 1593 V PINE LNE 0.0 W 0.0 var 1563 BIRDFERO 1596 RNGROCKS 1567 CONTY LN 1600 SREDING 1553 RORCST 1.06 pu 32.3 W 0.0 var 441.99 $/Wh 1730 TITUS -37.53 $/Wh 16.33 $/Wh 1607 TITUS 1608 TITUS 280.51 $/Wh 85.3 W -25.6 var 100% V 100% 187.23 $/Wh 1606 TITUS 1562 BIRDBORO -88.98 $/Wh 1575 K.B.I. 1556 BRTO 252.69 $/Wh 216.11 $/Wh 1164 SREDING -88.98 $/Wh 216.53 $/Wh 46.69 $/Wh 1.01 pu 17.20 $/Wh 129.35 $/Wh 1.00 pu 16.89 $/Wh 25.52 $/Wh 94% V 1566 CLOUSER 119.00 $/Wh 1.01 pu 4.0 W 0.0 var 0.0 W 0.0 var 106.35 $/Wh 1.00 pu 115.29 $/Wh 1.00 pu 1570 E.TOPTON 1574 GLENSIDE 1573 FRIEDNBG 4.2 W 0.0 var 29.00 $/Wh 95% V 95.95 $/Wh 1.01 pu 1569 E PENN 1576 KUTZTOWN 1729 SREDING 1565 CRSONI 1585 C-KN GP 31.69 $/Wh 109.34 $/Wh 1.00 pu 24.51 $/Wh 18.43 $/Wh 24.51 $/Wh 88.89 $/Wh 1.01 pu 1609 CORSTK T 1571 EXIDE 33.73 $/Wh 1555 BLDY 1572 FLYING H 1610 U.CORSTK 1.00 pu 1583 LYNNVILE 105.97 $/Wh 25.18 $/Wh 29.18 $/Wh 193.7 W 21.65 $/Wh 1.01 pu 1554 T&T 1599 S.HBRG 1584 LYONS 62.13 $/Wh V -16.4 var 1612 W.RDG 27.80 $/Wh 34.11 $/Wh 64.80 $/Wh 64.80 $/Wh 64.63 $/Wh 0.96 pu 24.05 $/Wh 1.01 pu 64.17 $/Wh 62.25 $/Wh 0.96 pu 61.10 $/Wh 0.96 pu 34.75 $/Wh 83% 1551 DSTWN 1564 CR TECH 1154 LYONS 1568 DN 1598 S.HBRG 1715 HILL RD 1716 1579 LINC 821 1604 SPG VL 1578 LEESPORT HILL RD 1717 PNTHER 1704 PNTHER 63.4 W 0.0 var 57.18 $/Wh 33.11 $/Wh 34.94 $/Wh 97% V 1580 LINC 822 1577 LEESPORT 57.18 $/Wh 75.00 $/Wh 1.01 pu 25.34 $/Wh 1.01 pu 34.94 $/Wh 25.73 $/Wh 1592 OUTR ST 1586 G IND 1587 G IND T 1557 BERK 24 54.67 $/Wh 1561 BERNVILL 58.09 $/Wh 1588 OSELE 1.01 pu 1581 LINCOLN 1603 SION TP 54.04 $/Wh 1560 BERN CH 53.35 $/Wh 69.42 $/Wh 16.4 W -3.3 var 1589 UHLENBG 36.13 $/Wh 41.58 $/Wh 1602 SION 54.04 $/Wh 1605 ST PETRS 43.11 $/Wh 1558 BERK 835 50.00 $/Wh 1597 ROSEDLE 1595 RIVRVIEW 49.44 $/Wh 1559 BERKLEY 50.00 $/Wh 1.06 pu 63.23 $/Wh 1.01 pu 12.6 W 5.0 var 1591 NTEPLE 1552 LTN CT 57.67 $/Wh 1.01 pu 1159 NTEPLE 268.5 W -35.7 var 43
V V 18.80 var V V V V 100% V V V V 100% V V V V V V V V V V V V V V V V V V V V 94% V V V V V V 95% V V V V V V V V V V V V V V V V V 83% V V V V V V V V V V V V V V 97% V V V V V V V V V V V V V V V V V V V V V V V V V V V V V Contour of Prices around Birdboro Pine Lane Load Pocket These prices could be reasonable. 15.47 $/Wh 1.06 pu 15.59 $/Wh 1.06 pu 1731 TITUS 35.9 W 16.33 $/Wh 0.0 var 15.59 $/Wh 1732 1.06 pu TITUS 32.3 W 0.0 var 16.24 $/Wh 441.99 $/Wh 32.3 W 0.0 var 1730 TITUS -37.53 $/Wh 16.33 $/Wh 1607 TITUS 1608 TITUS 1593-81.03 $/Wh 1582 LORNE 1606 TITUS 1562 BIRDBORO -88.98 $/Wh 1563 BIRDFERO 1164 SREDING 46.69 $/Wh 1.01 pu 1600 SREDING 1553 RORCST 16.89 $/Wh 17.20 $/Wh -88.98 $/Wh 25.52 $/Wh 4.0 W 0.0 var 4.2 W 0.0 var 1574 GLENSIDE 1729 SREDING 24.51 $/Wh 18.43 $/Wh 24.51 $/Wh 1610 U.CORSTK 1609 CORSTK T 1572 FLYING H 25.18 $/Wh 29.18 $/Wh 21.65 $/Wh 1.01 pu 24.05 $/Wh 1.01 pu 1612 W.RDG 27.80 $/Wh 1551 DSTWN 1568 DN 1564 CR TECH 1579 LINC 821 25.73 $/Wh 1580 LINC 822 25.34 $/Wh 1.01 pu 16.4 W -3.3 var 1581 LINCOLN 43.11 $/Wh 12.6 W 5.0 var 1595 RIVRVIEW PINE LNE 0.0 W 0.0 var 29.00 $/Wh 1565 CRSONI 33.11 $/Wh 1592 OUTR ST 1596 64.53 $/Wh 1156 NBOYERTO 1611 W.BOYTWN RNGROCKS 252.69 $/Wh 1585 C-KN GP 31.69 $/Wh 34.94 $/Wh 1586 G IND 1589 57.67 $/Wh 1159 280.51 $/Wh 1567 CONTY LN 216.53 $/Wh 34.75 $/Wh 1604 SPG VL 34.94 $/Wh 1587 G IND T UHLENBG 36.13 $/Wh 1.01 pu NTEPLE 1590 NBOYERTO 207.74 $/Wh 1575 K.B.I. 216.11 $/Wh 1571 EXIDE 33.73 $/Wh 1554 T&T 34.11 $/Wh 41.58 $/Wh 1597 ROSEDLE 49.44 $/Wh 268.5 W -35.7 var 1591 NTEPLE 1573 85.3 W -25.6 var FRIEDNBG 95.95 $/Wh 1.01 pu 0.0 W 0.0 var 1599 S.HBRG 64.80 $/Wh 1578 LEESPORT 57.18 $/Wh 1577 LEESPORT 1557 BERK 24 54.67 $/Wh 1603 SION TP 54.04 $/Wh 1602 SION 54.04 $/Wh 1566 CLOUSER 119.00 $/Wh 57.18 $/Wh 1.01 pu 64.80 $/Wh 1598 1558 S.HBRG BERK 835 50.00 $/Wh 106.35 $/Wh 1569 88.89 $/Wh 1.01 pu 1583 LYNNVILE 64.63 $/Wh 64.17 $/Wh 1715 HILL RD 1716 1561 BERNVILL 58.09 $/Wh 1560 BERN CH 53.35 $/Wh 1559 1.00 pu E PENN 0.96 pu HILL RD BERKLEY 187.23 $/Wh 1556 BRTO 109.34 $/Wh 1.00 pu 1555 BLDY 62.25 $/Wh 0.96 pu 61.10 $/Wh 0.96 pu 1717 PNTHER 1704 PNTHER 50.00 $/Wh 1.06 pu 63.23 $/Wh 1552 1.01 pu LTN CT 63.4 W 0.0 var 115.29 $/Wh 1.00 pu 1576 KUTZTOWN 193.7 W -16.4 var 75.00 $/Wh 1.01 pu 1588 OSELE 69.42 $/Wh 1.01 pu 1605 ST PETRS 129.35 $/Wh 1.00 pu 1570 E.TOPTON 105.97 $/Wh 1.00 pu 1584 LYONS 62.13 $/Wh 1154 LYONS 8: LP Large System 44
Unenforceable Constraints Summary Look for radial systems and load pockets Look for generators or phase shifters which can relieve problems Give the OPF more controls to FIX the problems Look for constraints which don t make sense Radial lines serving load Radial transformers/lines leaving generators Use your judgment to setup a reasonable case Realize that some unenforceable constraints are inevitable at first 8: LP Large System 45
Eastern.pwb Insufficient Reserves Load Eastern.pwb and 08 LP Large System\aux1000aster.aux, then solve LP OPF In this example, rea 28 (JCP&L) does not have enough GCable generation essage Log: Insufficient controls to enforce area constraint 8: LP Large System 46
Insufficient Reserves: Tips Examine Generator records or rea field Gen W GC Range Up To resolve Commit more generation ake more generation GCable, or designate some units as OPF Fast Start Increase imports, or make rea part of a Super rea Decrease load, or make load dispatchable 8: LP Large System 47
08EasternWidereaarket.pwb Too uch Power Transfer In the OPF solution, a linear program (LP) iterates with the non linear power flow to achieve convergence of the entire solution If an C OPF is performed over a very large rea (or Super rea), the LP may dispatch generators in a manner that exceeds voltage stability margins WECC cases may be especially susceptible 8: LP Large System 48
Too uch Power Transfer Example: Northern and a Southern section of the eastern interconnection are modeled as one ISO market (Super rea) North: includes eastern PJ, EP, First Energy South: includes TV, Southern Company, Entergy ssume generation much less expensive in the south, so LP OPF will initially try to increase the transfer from south to north OPF may exceed stability margin of power flow Load 08EasternWidereaarket.pwb, then solve LP OPF 8: LP Large System 49
Too uch Power Transfer Excerpt from essage Log LP attempts massive power transfer Game Over! 8: LP Large System 50
Too uch Power Transfer: Tips Tighten W Limits on generators with unrealistic limits (e.g. ax W = 9999): in this example, GC is set to NO for such units Place less of the system on OPF control Use interface limits Break a large area (or super area) into two or more smaller areas; use OPF dispatchable transactions between the smaller areas anually move generation in the direction of the LP transfer, resolve power flow, restart OPF Use DC Power Flow 8: LP Large System 51
OPF Dispatchable Transactions Example: Break WG super area into Northern and Southern super areas Reopen 08EasternWidereaarket.pwb and load 08_LP Large System\EasternNorthSouthSuperreas.aux dd a new transaction between a Northern area (e.g. EP) and a Southern area (e.g. TV) Set W limits on the new transaction and make it Dispatchable in OPF If OPF and power flow solve, try increasing the limits of the new transaction stop when the power flow will not converge 8: LP Large System 52
OPF Dispatchable Transactions South North transaction limited to 500 W beyond base case transfer OPF determines optimal transaction. If transaction is non binding at the solution, then areas are acting as a single super area. 8: LP Large System 53
anually ove Generation Reopen 08EasternWidereaarket.pwb Solve a Single Outer Loop of the OPF Look at OPF controls following the failure ove generation in direction of transfer (e.g. 10% of the transfer) ttempt to resolve the OPF Often additional transmission constraints will become binding before the full transfer is made OPF will know to move in a different direction 8: LP Large System 54
anually ove Generation: OPF Controls 8: LP Large System 55
Use a spreadsheet to step the transfer (Generatordjust.xls) Set GenW = Orig. Value + Delta Value * Percent ove 1. Copy OPF controls to the spreadsheet 2. Paste Gen Records back into Simulator, solve power flow, and restart LP OPF anually ove Generation: Spreadsheet 8: LP Large System 56