ECE 530 – Analysis Techniques for Large-Scale Electrical Systems Prof. Tom Overbye Dept. of...

ECE 530 – Analysis Techniques for Large-Scale Electrical Systems

Prof. Tom Overbye

Dept. of Electrical and Computer Engineering

University of Illinois at Urbana-Champaign

[email protected]/21/2015

1

Lecture 8: Power System Operation

Power System Operations Overview

• Goal is to provide an intuitive feel for power system operation

• Emphasis will be on the impact of the transmission system

• Introduce basic power flow concepts through small system examples

2

Power System Basics

• All power systems have three major components: Generation, Load and Transmission/Distribution.

• Generation: Creates electric power.• Load: Consumes electric power.• Transmission/Distribution: Transmits electric

power from generation to load. –Lines/transformers operating at voltages above

100 kV are usually called the transmission system. The transmission system is usually networked.

–Lines/transformers operating at voltages below 100 kV are usually called the distribution system (radial).

3

Metro Chicago Electric Network

4

Small PowerWorld Simulator Case

Bus 2 Bus 1

Bus 3Home Area

204 MW

102 MVR

150 MW

150 MW 37 MVR

116 MVR

102 MW 51 MVR

1.00 PU

-20 MW 4 MVR

20 MW -4 MVR

-34 MW 10 MVR

34 MW-10 MVR

14 MW -4 MVR

-14 MW

4 MVR

1.00 PU

1.00 PU

106 MW 0 MVR

100 MWAGC ONAVR ON

AGC ONAVR ON

Load withgreenarrows indicatingamountof MWflow

Usedto controloutput ofgenerator

Direction of arrow is used to indicatedirection of real power (MW) flow

Note thepower balance ateach bus

PowerWorld Case: B3NewSlow 5

Basic Power Control

6

• Opening a circuit breaker causes the power flow to instantaneously (nearly) change.

• No other way to directly control power flow in a transmission line.

• By changing generation we can indirectly change this flow.

• Power flow in transmission line is limited by heating considerations

• Losses (I^2 R) can heat up the line, causing it to sag.

Overloaded Transmission Line

7

Interconnected Operation

• Power systems are interconnected across large distances. For example most of North America east of the Rockies is one system, with most of Texas and Quebec being major exceptions

• Individual utilities only own and operate a small portion of the system; this paradigm is nowmore complex withthe advent of ISOs 8

Balancing Authority (BA) Areas

• Transmission lines that join two areas are known as tie-lines.

• The net power out of an area is the sum of the flow on its tie-lines.

• The flow out of an area is equal to

total gen - total load - total losses = tie-flow

9

Area Control Error (ACE)

• The area control error is the difference between the actual flow out of an area, and the scheduled flow–ACE also includes a frequency component that we

will probably consider later in the semester

• Ideally the ACE should always be zero• Because the load is constantly changing, each

utility (or ISO) must constantly change its generation to “chase” the ACE

• ACE was originally computed by utilities; increasingly it is computed by larger organizations such as ISOs

10

Area Control Error (ACE)

• The area control error is the difference between the actual flow out of an area, and the scheduled flow–ACE also includes a frequency component that we

will probably consider later in the semester

• Ideally the ACE should always be zero• Because the load is constantly changing, each

utility (or ISO) must constantly change its generation to “chase” the ACE

• ACE was originally computed by utilities; increasingly it is computed by larger organizations such as ISOs

11

Automatic Generation Control

• Most utilities (ISOs) use automatic generation control (AGC) to automatically change their generation to keep their ACE close to zero.

• Usually the control center calculates ACE based upon tie-line flows; then the AGC module sends control signals out to the generators every couple seconds.

12

Three Bus Case on AGC

Bus 2 Bus 1

Bus 3Home Area

266 MW

133 MVR

150 MW

250 MW 34 MVR

166 MVR

133 MW 67 MVR

1.00 PU

-40 MW 8 MVR

40 MW -8 MVR

-77 MW 25 MVR

78 MW-21 MVR

39 MW-11 MVR

-39 MW

12 MVR

1.00 PU

1.00 PU

101 MW 5 MVR

100 MWAGC ONAVR ON

AGC ONAVR ON

Net tie flow is close to zero

Generationis automaticallychanged to matchchange in load

13

Generator Costs

• There are many fixed and variable costs associated with power system operation

• The major variable cost is associated with generation.

• Cost to generate a MWh can vary widely• For some types of units (such as hydro and

nuclear) it is difficult to quantify• More others such as wind and solar the marginal

cost of energy is essentially zero (actually negative for wind!)

• For thermal units it is straightforward to determine

• Many markets have moved from cost-based to price-based generator costs

14

Economic Dispatch

• Economic dispatch (ED) determines the least cost dispatch of generation for an area.

• For a lossless system, the ED occurs when all the generators have equal marginal costs.

IC1(PG,1) = IC2(PG,2) = … = ICm(PG,m)

15

Power Transactions

• Power transactions are contracts between areas to do power transactions.

• Contracts can be for any amount of time at any price for any amount of power.

• Scheduled power transactions are implemented by modifying the area ACE:

ACE = Pactual,tie-flow - Psched

16

100 MW Transaction

Bus 2 Bus 1

Bus 3Home Area

Scheduled Transactions

225 MW

113 MVR

150 MW

291 MW 8 MVR

138 MVR

113 MW 56 MVR

1.00 PU

8 MW -2 MVR

-8 MW 2 MVR

-84 MW 27 MVR

85 MW-23 MVR

93 MW-25 MVR

-92 MW

30 MVR

1.00 PU

1.00 PU

0 MW 32 MVR

100 MWAGC ONAVR ON

AGC ONAVR ON

100.0 MW

Scheduled 100 MWTransaction from Left to Right

Net tie-lineflow is now100 MW

17

Security Constrained ED

• Transmission constraints often limit system economics.

• Such limits required a constrained dispatch in order to maintain system security.

• In three bus case the generation at bus 3 must be constrained to avoid overloading the line from bus 2 to bus 3.

18

Security Constrained Dispatch

Bus 2 Bus 1

Bus 3Home Area

Scheduled Transactions

357 MW

179 MVR

194 MW

448 MW 19 MVR

232 MVR

179 MW 89 MVR

1.00 PU

-22 MW 4 MVR

22 MW -4 MVR

-142 MW 49 MVR

145 MW-37 MVR

124 MW-33 MVR

-122 MW

41 MVR

1.00 PU

1.00 PU

0 MW 37 MVR100%

100%

100 MWOFF AGCAVR ON

AGC ONAVR ON

100.0 MW

Dispatch is no longer optimal due to need to keep line from bus 2 to bus 3 from overloading

19

Multi-Area Operation

• If Areas have direct interconnections, then they may directly transact up to the capacity of their tie-lines.

• Actual power flows through the entire network according to the impedance of the transmission lines.

• Flow through other areas is known as “parallel path” or “loop flows.”

20

Seven Bus Case: One-line

Top Area Cost

Left Area Cost Right Area Cost

1

2

3 4

5

6 7

106 MW

168 MW

200 MW 201 MW

110 MW 40 MVR

80 MW 30 MVR

130 MW 40 MVR

40 MW 20 MVR

1.00 PU

1.01 PU

1.04 PU1.04 PU

1.04 PU

0.99 PU1.05 PU

62 MW

-61 MW

44 MW -42 MW -31 MW 31 MW

38 MW

-37 MW

79 MW -77 MW

-32 MW

32 MW-14 MW

-39 MW

40 MW-20 MW 20 MW

40 MW

-40 MW

94 MW

200 MW 0 MVR

200 MW 0 MVR

20 MW -20 MW

AGC ON

AGC ON

AGC ON

AGC ON

AGC ON

8029 $/MWH

4715 $/MWH 4189 $/MWH

Case Hourly Cost 16933 $/MWH

System hasthree areas

Area Lefthas onebus

Area Right has one bus

Area Tophas fivebuses

PowerWorld Case: B7Flat 21

Seven Bus Case: Area View

System has40 MW of“Loop Flow”

Actualflowbetweenareas

Loop flow can result in higher losses

Area Losses

Area Losses Area Losses

Top

Left Right

-40.1 MW

0.0 MW

0.0 MW

0.0 MW

40.1 MW

40.1 MW

7.09 MW

0.33 MW 0.65 MW

Scheduledflow

22

Seven Bus - Loop Flow?

Area Losses

Area Losses Area Losses

Top

Left Right

-4.8 MW

0.0 MW

100.0 MW

0.0 MW

104.8 MW

4.8 MW

9.44 MW

-0.00 MW 4.34 MW

100 MW Transactionbetween Left and Right

Transaction has actually decreasedthe loop flow

Note thatTop’s Losses haveincreasedfrom 7.09MW to9.44 MW

23

POWER TRANSFER DISTRIBUTION FACTORS (PTDFS)

24

• PTDFs are used to show how a particular transaction will affect the system

• Power transfers through the system according to the impedances of the lines, without respect to ownership

• All transmission players in network could be impacted, to a greater or lesser extent

• Later in the semester we’ll consider techniques for calculating PTDFs

PTDF EXAMPLE - NINE BUS CASE ACTUAL FLOWS

25

17%

58% 41%

51%

45%

42%

34%

6%

54%

29%

32%

A

G

B

C

D

E

I

F

H

400.0 MWMW 400.0 MWMW 300.0 MWMW

250.0 MWMW

250.0 MWMW

200.0 MWMW

250.0 MWMW

150.0 MWMW

50.0 MW

39%

PowerWorld Case: B9

PTDF EXAMPLE - PTDFS: TRANSFER FROM A TO I

26

44%

56% 13%

30%

35%

20%

10%

2%

34%

34%

32%

A

G

B

C

D

E

I

F

H

400.0 MWMW 400.0 MWMW 300.0 MWMW

250.0 MWMW

250.0 MWMW

200.0 MWMW

250.0 MWMW

150.0 MWMW

50.0 MW

34%

Values now tell percentage of flow that will go on line

PTDF EXAMPLE - PTDFS: TRANSFER FROM G TO F

27

6%

6% 12%

18%

61%

12%

6%

19%

21%

21%

A

G

B

C

D

E

I

F

H

400.0 MWMW 400.0 MWMW 300.0 MWMW

250.0 MWMW

250.0 MWMW

200.0 MWMW

250.0 MWMW

150.0 MWMW

50.0 MW

20%

Wisconsin to TVA Line PTDF Contour

28

Contours show lines that would carry at least 2% of a power transfer from Wisconsin to TVA

NERC Flowgates

• A convenient glossary of terms used for power system operations in North America is available at http://www.nerc.com/files/glossary_of_terms.pdf

• One common term is a “flowgate,” which is a mathematical construct to measure the MW flow on one or more elements in the bulk transmission system–Sometimes they include the impact of contingencies,

something we will consider later in the semester

• A simple flowgate would be the MW flow through a single transmission line or transformer

29

NERC TLRs

• In the North American Eastern Interconnect (EI) transmission loading relief procedures (TLRs) are used to mitigate the overloads on the bulk transmission system

• TLRs consider the PTDFs associated with transactions on flowgates if there is a flowgate violation

30

Loop Flow Impact: Market Segmentation

31

T V A

SOUTHERN

AEP

CPLW

AP

JCP&LPECO

AE

PSE&G

AEC

SMEPA

CEI

CINCIPS

CONS

DECO

CPLE

DLCO

DPL

DUKE

EKPC

IMPA

IP

IPL

KU

NI

NIPS

OE

OVEC

TE

VP

METED

PENELEC

PEPCO

PJM500

BG&E

PP&L

BREC

LGE

SIGE

SIPC

CILCO

CWLP

HE

EEI

EMO

NYPP

SCE&GSCPSA

ONT HYDR

DOE

DPL

ENTR

NEPOOL

WPLWEP

WPS

UPP

MGE

YADKIN

HARTWELL

SEPA-JST

SEPA-RBR

TAL

FPC

FPL

JEA

SECCELE

LAFA

CAJN

SWEP

SWPA

PSOK

GRRD

OKGE

KAMO

SWPS

WEFA

OMPA

EQ-ERCOT

WERE

NSP

MP

IPW

DPC

MEC

IESC

MPW

OTP

NPPD OPPD

SMP

UPA

WAPA

MIPUSTJOKACY

KACP

ASEC

SPRM

INDN

EMDE

MIDWSUNC

WEPL

During summerof 1998 con-gestion on justtwo elementspushed Midwestspot marketprices up by afactor of 200:from $ 20/MWhto $ 7500/MWh!

Large price rises have occurred in 1999 and 2000 as well

Pricing Electricity

• Cost to supply electricity to bus is called the locational marginal price (LMP)

• Presently some electric makets post LMPs on the web

• In an ideal electricity market with no transmission limitations the LMPs are equal

• Transmission constraints can segment a market, resulting in differing LMP

• Determination of LMPs requires the solution on an Optimal Power Flow (OPF)

32

3 BUS LMPS - OVERLOAD IGNORED

Bus 2 Bus 1

Bus 3

Total Cost

0 MW

0 MW

180 MWMW

10.00 $/MWh

60 MW 60 MW

60 MW

60 MW120 MW

120 MW

10.00 $/MWh

10.00 $/MWh

180 MW120%

120%

0 MWMW

1800 $/hr

Line from Bus 1 to Bus 3 is over-loaded; all buses have same marginal cost

Gen 1’scostis $10per MWh

Gen 2’scostis $12per MWh

PowerWorld Case: B3LP 33

LINE OVERLOAD ENFORCED

Bus 2 Bus 1

Bus 3

Total Cost

60 MW

0 MW

180 MWMW

12.00 $/MWh

20 MW 20 MW

80 MW

80 MW100 MW

100 MW

10.00 $/MWh

14.01 $/MWh

120 MW 80% 100%

80% 100%

0 MWMW

1921 $/hr

Line from 1 to 3 is no longer overloaded, but nowthe marginal cost of electricity at 3 is $14 / MWh 34

MISO LMPs

35

Five minuteLMPs areposted onlinefor the MISOfootprint

Source: https://www.misoenergy.org/LMPContourMap/MISO_MidWest.html

MISO LMP Volatility!

36

Thisis howthe LMPcontourlookedfor the next 5minuteupdate!

37 Bus Example Design Case

This is Design Case 2 From Chapter 6 of Power System Analysis andDesign by Glover, Sarma, and Overbye, 4th Edition, 2008

Metropolis Light and Power Electric Design Case 2SLACK345

SLACK138

RAY345

RAY138

RAY69

FERNA69

A

MVA

DEMAR69

BLT69

BLT138

BOB138

BOB69

WOLEN69

SHI MKO69

ROGER69

UI UC69

PETE69HI SKY69

TI M69

TI M138

TI M345

PAI 69

GROSS69

HANNAH69

AMANDA69

HOMER69

LAUF69

MORO138

LAUF138

HALE69

PATTEN69

WEBER69

BUCKY138

SAVOY69

SAVOY138

J O138 J O345

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

1.03 pu

1.02 pu

1.03 pu

1.03 pu

1.01 pu

1.00 pu1.01 pu

1.00 pu

1.02 pu

1.01 pu

1.00 pu

1.01 pu

1.01 pu

1.01 pu

1.01 pu

1.02 pu

1.00 pu

1.00 pu

1.02 pu

0.99 pu

0.99 pu

1.00 pu

1.02 pu

1.00 pu1.01 pu

1.01 pu

1.00 pu 1.00 pu

1.01 pu

1.02 pu 1.02 pu

1.02 pu 1.03 pu

A

MVA

1.02 pu

A

MVA

A

MVA

LYNN138

A

MVA

1.02 pu

A

MVA

1.00 pu

A

MVA

System Losses: 10.70 MW

220 MW 52 Mvar

12 MW 3 Mvar

20 MW 12 Mvar

124 MW 45 Mvar

37 MW

13 Mvar

12 MW 5 Mvar

150 MW 0 Mvar

56 MW

13 Mvar

15 MW 5 Mvar

14 MW

2 Mvar

38 MW 3 Mvar

45 MW 0 Mvar

25 MW 36 Mvar

36 MW 10 Mvar

10 MW 5 Mvar

22 MW 15 Mvar

60 MW 12 Mvar

20 MW 28 Mvar

23 MW 7 Mvar

33 MW 13 Mvar

15.9 Mvar 18 MW 5 Mvar

58 MW 40 Mvar

60 MW 19 Mvar

14.2 Mvar

25 MW 10 Mvar

20 MW 3 Mvar

23 MW 6 Mvar 14 MW

3 Mvar

4.9 Mvar

7.3 Mvar

12.8 Mvar

28.9 Mvar

7.4 Mvar

0.0 Mvar

55 MW 25 Mvar

39 MW 13 Mvar

150 MW 0 Mvar

17 MW 3 Mvar

16 MW -14 Mvar

14 MW 4 Mvar

KYLE69A

MVA

PowerWorld Case: TD_2012_Design2 37

Good Power System Operation

• Good power system operation requires that there be no reliability violations for either the current condition or in the event of statistically likely contingencies–Reliability requires as a minimum that there be no

transmission line/transformer limit violations and that bus voltages be within acceptable limits (perhaps 0.95 to 1.08)

–Example contingencies are the loss of any single device. This is known as n-1 reliability.

38

Looking at the Impact of Line Outages

slack


SLACK138

RAY345

RAY138

RAY69

FERNA69

A

MVA

DEMAR69

BLT69

BLT138

BOB138

BOB69

WOLEN69

SHI MKO69

ROGER69

UI UC69

PETE69HI SKY69

TI M69

TI M138

TI M345

PAI 69

GROSS69

HANNAH69

AMANDA69

HOMER69

LAUF69

MORO138

LAUF138

HALE69

PATTEN69

WEBER69

BUCKY138

SAVOY69

SAVOY138

J O138 J O345

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

1.03 pu

1.02 pu

1.03 pu

1.03 pu

1.01 pu

1.00 pu1.01 pu

1.00 pu

1.02 pu

1.01 pu

1.00 pu

1.01 pu

1.01 pu

1.01 pu

1.01 pu

1.02 pu

1.01 pu

1.00 pu

1.02 pu

0.90 pu

0.90 pu

0.94 pu

1.01 pu

0.99 pu1.00 pu

1.00 pu

1.00 pu 1.00 pu

1.01 pu

1.01 pu 1.02 pu

1.02 pu 1.03 pu

A

MVA

1.02 pu

A

MVA

A

MVA

LYNN138

A

MVA

1.02 pu

A

MVA

1.00 pu

A

MVA


227 MW 43 Mvar

12 MW 3 Mvar

20 MW 12 Mvar

124 MW 45 Mvar

37 MW

13 Mvar

12 MW 5 Mvar

150 MW 4 Mvar

56 MW

13 Mvar

15 MW 5 Mvar

14 MW

2 Mvar

38 MW 9 Mvar

45 MW 0 Mvar

25 MW 36 Mvar

36 MW 10 Mvar

10 MW 5 Mvar

22 MW 15 Mvar

60 MW 12 Mvar

20 MW 40 Mvar

23 MW 7 Mvar

33 MW 13 Mvar


58 MW 40 Mvar

60 MW 19 Mvar

11.6 Mvar

25 MW 10 Mvar

20 MW 3 Mvar

23 MW 6 Mvar 14 MW

3 Mvar

4.9 Mvar

7.2 Mvar

12.8 Mvar

28.9 Mvar

7.3 Mvar

0.0 Mvar

55 MW 32 Mvar

39 MW 13 Mvar

150 MW 4 Mvar

17 MW 3 Mvar

16 MW -14 Mvar

14 MW 4 Mvar

KYLE69A

MVA

80%A

MVA

135%A

MVA

110%A

MVA

Opening one line (Tim69-Hannah69) causes an overload. This would not be allowed 39

Contingency Analysis

Contingencyanalysis providesan automaticway of lookingat all the statisticallylikely contingencies. Inthis example thecontingency setIs all the single line/transformeroutages

40

Power Flow And Design

• One common usage of the power flow is to determine how the system should be modified to remove contingencies problems or serve new load–In an operational context this requires working with

the existing electric grid–In a planning context additions to the grid can be

considered• In the next example we look at how to remove the

existing contingency violations while serving new load.

41

An Unreliable Solution

slack


SLACK138

RAY345

RAY138

RAY69

FERNA69

A

MVA

DEMAR69

BLT69

BLT138

BOB138

BOB69

WOLEN69

SHI MKO69

ROGER69

UI UC69

PETE69HI SKY69

TI M69

TI M138

TI M345

PAI 69

GROSS69

HANNAH69

AMANDA69

HOMER69

LAUF69

MORO138

LAUF138

HALE69

PATTEN69

WEBER69

BUCKY138

SAVOY69

SAVOY138

J O138 J O345

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

1.02 pu

1.01 pu

1.02 pu

1.03 pu

1.01 pu

1.00 pu1.01 pu

1.00 pu

1.02 pu

1.01 pu

1.00 pu

1.01 pu

1.01 pu

1.01 pu

1.01 pu

1.02 pu

0.99 pu

1.00 pu

1.02 pu

0.97 pu

0.97 pu

0.99 pu

1.02 pu

1.00 pu1.01 pu

1.01 pu

1.00 pu 1.00 pu

1.01 pu

1.02 pu 1.02 pu

1.02 pu 1.03 pu

A

MVA

1.02 pu

A

MVA

A

MVA

LYNN138

A

MVA

1.02 pu

A

MVA

1.00 pu

A

MVA


269 MW 67 Mvar

12 MW 3 Mvar

20 MW 12 Mvar

124 MW 45 Mvar

37 MW

13 Mvar

12 MW 5 Mvar

150 MW 1 Mvar

56 MW

13 Mvar

15 MW 5 Mvar

14 MW

2 Mvar

38 MW 4 Mvar

45 MW 0 Mvar

25 MW 36 Mvar

36 MW 10 Mvar

10 MW 5 Mvar

22 MW 15 Mvar

60 MW 12 Mvar

20 MW 40 Mvar

23 MW 7 Mvar

33 MW 13 Mvar


58 MW 40 Mvar

60 MW 19 Mvar

13.6 Mvar

25 MW 10 Mvar

20 MW 3 Mvar

23 MW 6 Mvar 14 MW

3 Mvar

4.9 Mvar

7.3 Mvar

12.8 Mvar

28.9 Mvar

7.4 Mvar

0.0 Mvar

55 MW 28 Mvar

39 MW 13 Mvar

150 MW 1 Mvar

17 MW 3 Mvar

16 MW -14 Mvar

14 MW 4 Mvar

KYLE69A

MVA

96%A

MVA

Case now has nine separate contingencies with reliability violations 42

A Reliable Solution

slack


SLACK138

RAY345

RAY138

RAY69

FERNA69

A

MVA

DEMAR69

BLT69

BLT138

BOB138

BOB69

WOLEN69

SHI MKO69

ROGER69

UI UC69

PETE69HI SKY69

TI M69

TI M138

TI M345

PAI 69

GROSS69

HANNAH69

AMANDA69

HOMER69

LAUF69

MORO138

LAUF138

HALE69

PATTEN69

WEBER69

BUCKY138

SAVOY69

SAVOY138

J O138 J O345

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

1.03 pu

1.01 pu

1.02 pu

1.03 pu

1.01 pu

1.00 pu1.01 pu

1.00 pu

1.02 pu

1.01 pu

1.00 pu

1.01 pu

1.01 pu

1.01 pu

1.01 pu

1.02 pu

1.00 pu

0.99 pu

1.02 pu

0.99 pu

0.99 pu

1.00 pu

1.02 pu

1.00 pu1.01 pu

1.01 pu

1.00 pu 1.00 pu

1.01 pu

1.02 pu 1.02 pu

1.02 pu 1.03 pu

A

MVA

1.02 pu

A

MVA

A

MVA

LYNN138

A

MVA

1.02 pu

A

MVA

A

MVA


266 MW 59 Mvar

12 MW 3 Mvar

20 MW 12 Mvar

124 MW 45 Mvar

37 MW

13 Mvar

12 MW 5 Mvar

150 MW 1 Mvar

56 MW

13 Mvar

15 MW 5 Mvar

14 MW

2 Mvar

38 MW 4 Mvar

45 MW 0 Mvar

25 MW 36 Mvar

36 MW 10 Mvar

10 MW 5 Mvar

22 MW 15 Mvar

60 MW 12 Mvar

20 MW 38 Mvar

23 MW 7 Mvar

33 MW 13 Mvar


58 MW 40 Mvar

60 MW 19 Mvar

14.1 Mvar

25 MW 10 Mvar

20 MW 3 Mvar

23 MW 6 Mvar 14 MW

3 Mvar

4.9 Mvar

7.3 Mvar

12.8 Mvar

28.9 Mvar

7.4 Mvar

0.0 Mvar

55 MW 29 Mvar

39 MW 13 Mvar

150 MW 1 Mvar

17 MW 3 Mvar

16 MW -14 Mvar

14 MW 4 Mvar

KYLE69A

MVA

Kyle138A

MVA

Previous case was augmented with the addition of a 138 kV Transmission Line

43PowerWorld Case: TD_2012_Design2_ReliableDesign

Generation Changes and The Slack Bus

• The power flow is a steady-state analysis tool, so the assumption is total load plus losses is always equal to total generation–Generation mismatch is made up at the slack bus

• When doing generation change power flow studies one always needs to be cognizant of where the generation is being made up–Common options include system slack, distributed

across multiple generators by participation factors or by economics

44

Generation Change Example 1

slack

SLACK345

SLACK138

RAY345

RAY138

RAY69

FERNA69

A

MVA

DEMAR69

BLT69

BLT138

BOB138

BOB69

WOLEN69

SHI MKO69

ROGER69

UI UC69

PETE69

HI SKY69

TI M69

TI M138

TI M345

PAI 69

GROSS69

HANNAH69

AMANDA69

HOMER69

LAUF69

MORO138

LAUF138

HALE69

PATTEN69

WEBER69

BUCKY138

SAVOY69

SAVOY138

J O138 J O345

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

0.00 pu

-0.01 pu

0.00 pu

0.00 pu

0.00 pu

-0.03 pu-0.01 pu

0.00 pu

0.00 pu

0.00 pu

-0.03 pu

-0.01 pu0.00 pu

0.00 pu

0.00 pu

0.00 pu

0.00 pu

0.00 pu

0.00 pu

-0.002 pu

0.00 pu

0.00 pu

0.00 pu

0.00 pu0.00 pu

0.00 pu

0.00 pu 0.00 pu

0.00 pu

0.00 pu0.00 pu

0.00 pu0.00 pu

A

MVA

-0.01 pu

A

MVA

A

MVA

LYNN138

A

MVA

0.00 pu

A

MVA

0.00 pu

A

MVA

162 MW 35 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

-157 MW -45 Mvar

0 MW

0 Mvar

0 MW 0 Mvar

0 MW 2 Mvar

0 MW

0 Mvar

0 MW 0 Mvar

0 MW

0 Mvar

0 MW 3 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 4 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

-0.1 Mvar 0 MW 0 Mvar

0 MW 0 Mvar 0 MW

0 Mvar

-0.1 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar 0 MW

0 Mvar

-0.1 Mvar

0.0 Mvar

-0.1 Mvar

-0.2 Mvar

0.0 Mvar

0.0 Mvar

0 MW 51 Mvar

0 MW 0 Mvar

0 MW 2 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

45PowerWorld Case: TD_2012_37Bus_GenChange


slack

SLACK345

SLACK138

RAY345

RAY138

RAY69

FERNA69

A

MVA

DEMAR69

BLT69

BLT138

BOB138

BOB69

WOLEN69

SHI MKO69

ROGER69

UI UC69

PETE69

HI SKY69

TI M69

TI M138

TI M345

PAI 69

GROSS69

HANNAH69

AMANDA69

HOMER69

LAUF69

MORO138

LAUF138

HALE69

PATTEN69

WEBER69

BUCKY138

SAVOY69

SAVOY138

J O138 J O345

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

0.00 pu

-0.01 pu

0.00 pu

0.00 pu

0.00 pu

-0.03 pu-0.01 pu

0.00 pu

0.00 pu

0.00 pu

-0.03 pu

-0.01 pu0.00 pu

0.00 pu

0.00 pu

0.00 pu

0.00 pu

0.00 pu

0.00 pu

-0.002 pu

0.00 pu

0.00 pu

0.00 pu

0.00 pu0.00 pu

0.00 pu

0.00 pu 0.00 pu

0.00 pu

0.00 pu0.00 pu

0.00 pu0.00 pu

A

MVA

-0.01 pu

A

MVA

A

MVA

LYNN138

A

MVA

0.00 pu

A

MVA

0.00 pu

A

MVA

162 MW 35 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

-157 MW -45 Mvar

0 MW

0 Mvar

0 MW 0 Mvar

0 MW 2 Mvar

0 MW

0 Mvar

0 MW 0 Mvar

0 MW

0 Mvar

0 MW 3 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 4 Mvar

0 MW 0 Mvar

0 MW 0 Mvar


0 MW 0 Mvar 0 MW

0 Mvar

-0.1 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar 0 MW

0 Mvar

-0.1 Mvar

0.0 Mvar

-0.1 Mvar

-0.2 Mvar

0.0 Mvar

0.0 Mvar

0 MW 51 Mvar

0 MW 0 Mvar

0 MW 2 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

Display shows “Difference Flows” between original 37 bus case, and case with a BLT138 generation outage; note all the power change is picked up at the slack 46


slack

SLACK345

SLACK138

RAY345

RAY138

RAY69

FERNA69

A

MVA

DEMAR69

BLT69

BLT138

BOB138

BOB69

WOLEN69

SHI MKO69

ROGER69

UI UC69

PETE69

HI SKY69

TI M69

TI M138

TI M345

PAI 69

GROSS69

HANNAH69

AMANDA69

HOMER69

LAUF69

MORO138

LAUF138

HALE69

PATTEN69

WEBER69

BUCKY138

SAVOY69

SAVOY138

J O138 J O345

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

0.00 pu

-0.01 pu

0.00 pu

0.00 pu

0.00 pu

-0.03 pu0.00 pu

0.00 pu

0.00 pu

0.00 pu

-0.03 pu

-0.01 pu-0.01 pu

0.00 pu

0.00 pu

0.00 pu

0.00 pu

0.00 pu

0.00 pu

-0.003 pu

0.00 pu

0.00 pu

0.00 pu

0.00 pu0.00 pu

0.00 pu

0.00 pu 0.00 pu

0.00 pu

0.00 pu0.00 pu

0.00 pu0.00 pu

A

MVA

0.00 pu

A

MVA

A

MVA

LYNN138

A

MVA

0.00 pu

A

MVA

0.00 pu

A

MVA

0 MW 37 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

-157 MW -45 Mvar

0 MW

0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW

0 Mvar

0 MW 0 Mvar

0 MW

0 Mvar

42 MW -14 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

99 MW -20 Mvar

0 MW 0 Mvar

0 MW 0 Mvar


0 MW 0 Mvar 0 MW

0 Mvar

-0.1 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar 0 MW

0 Mvar

0.0 Mvar

0.0 Mvar

-0.1 Mvar

-0.2 Mvar

-0.1 Mvar

0.0 Mvar

19 MW 51 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

0 MW 0 Mvar

Display repeats previous case except now the change in generation is picked up by other generators using a participation factor approach 47

Generator Reactive Limits

• Generators are P-V buses (P and V are specified).

• QGi of generator i must be within specified limits

• During the PF solution process

• the bus is now a P-Q bus and the originally specified V at this bus is relaxed and calculated.

maxGG

minG iii

QQQ

maxGG ii

QQ If

minGG ii

QQ If minGG ii

QQ then

maxGG ii

QQ then

48

Voltage Regulation Example: 37 Buses

Display shows voltage contour of the power system, demo will show the impactof generator voltage set point, reactive power limits, and switched capacitors

slack

SLACK345

SLACK138

RAY345

RAY138

RAY69

FERNA69

A

MVA

DEMAR69

BLT69

BLT138

BOB138

BOB69

WOLEN69

SHI MKO69

ROGER69

UI UC69

PETE69

HI SKY69

TI M69

TI M138

TI M345

PAI 69

GROSS69

HANNAH69

AMANDA69

HOMER69

LAUF69

MORO138

LAUF138

HALE69

PATTEN69

WEBER69

BUCKY138

SAVOY69

SAVOY138

J O138 J O345

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVAA

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

A

MVA

1.03 pu

1.01 pu

1.02 pu

1.03 pu

1.01 pu

1.00 pu1.00 pu

0.99 pu

1.02 pu

1.01 pu

1.00 pu

1.01 pu1.01 pu

1.01 pu

1.01 pu

1.02 pu

1.00 pu

1.00 pu

1.02 pu

0.997 pu

0.99 pu

1.00 pu

1.02 pu

1.00 pu1.01 pu

1.00 pu

1.00 pu 1.00 pu

1.01 pu

1.02 pu1.02 pu

1.02 pu 1.03 pu

A

MVA

1.02 pu

A

MVA

A

MVA

LYNN138

A

MVA

1.02 pu

A

MVA

1.00 pu

A

MVA

219 MW 52 Mvar

21 MW 7 Mvar

45 MW 12 Mvar

157 MW 45 Mvar

37 MW

13 Mvar

12 MW 5 Mvar

150 MW 0 Mvar

56 MW

13 Mvar

15 MW 5 Mvar

14 MW

2 Mvar

38 MW 3 Mvar

45 MW 0 Mvar

58 MW 36 Mvar

36 MW 10 Mvar

0 MW 0 Mvar

22 MW 15 Mvar

60 MW 12 Mvar

20 MW 9 Mvar

23 MW 7 Mvar

33 MW 13 Mvar 15.9 Mvar 18 MW

5 Mvar

58 MW 40 Mvar 51 MW

15 Mvar

14.3 Mvar

33 MW

10 Mvar

15 MW 3 Mvar

23 MW 6 Mvar 14 MW

3 Mvar

4.8 Mvar

7.2 Mvar

12.8 Mvar

29.0 Mvar

7.4 Mvar

20.8 Mvar

92 MW 10 Mvar

20 MW 8 Mvar

150 MW 0 Mvar

17 MW 3 Mvar

0 MW 0 Mvar

14 MW 4 Mvar

1.010 pu 0.0 Mvar


49PowerWorld Case: TD_2012_37Bus_Voltage

Remote Regulation and Reactive Power Sharing

• It is quite common for a generator to control the voltage for a location that is not its terminal–Sometimes this is on the high side of the generator step-up

transformer (GSU), sometimes it is partway through the GSU

• It is also quite common for multiple generators to regulate the same bus voltage– In this case only one of the generators can be set as a PV bus;

the others must be set as PQ, with the total reactive power output allocated among them

–Different methods can be used for allocating reactive power among multiple generators

50

Multiple PV Generator Regulation

51

Top Area Cost

Left Area Cost Right Area Costslack

0.98 pu

1.00 pu

1.04 pu1.04 pu

1.03 pu

0.97 pu1.05 pu

A

MVA

A

MVA

A

MVAA

MVA

A

MVA

A

MVA A

MVA

A

MVA

A

MVA

A

MVA

64 MW

63 MW

44 MW 42 MW 32 MW 32 MW

37 MW

36 MW

79 MW 77 MW

31 MW

31 MW

14 MW

39 MW

40 MW 20 MW 21 MW

40 MW

39 MW

A

MVA

21 MW 20 MW

8043 $/h

4677 $/h 4222 $/h

Case Hourly Cost 16943 $/h

Bus 1 Bus 3 Bus 4

Bus 2 Bus 5

Bus 6 Bus 7

MW108

MW164

MW202 MW199

110 MW

80 MW

130 MW 40 MW

MW 96

200 MW

0 Mvar200 MW

0 Mvar

AGC ON

AGC ON

AGC ON

AGC ON

AGC ON

PowerWorld Case: B7Flat_MultipleGenReg

In this caseboth theBus 2 andBus 4 gensare set to regulatethe Bus 5voltage. Note, theymust regulate itto the samevalue!!

ECE 530 – Analysis Techniques for Large-Scale Electrical Systems Prof. Tom Overbye Dept. of...

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Transcript of ECE 530 – Analysis Techniques for Large-Scale Electrical Systems Prof. Tom Overbye Dept. of...