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9/13/2011
1
Efficiency and Home Energy Use• Whole-house energy efficiency approach –
find out which parts consume the most energy
Energy Systems Research Laboratory, FIU
http://www1.eere.energy.gov/consumer/tips/home_energy.html
Clean, Green Coal• “Clean coal” is a vague term that refers to a number of
processes by which coal can be used to make electricity with less “pollution.”
• These technologies include
– Electrostatic precipitators, which remove particles from the flue gases. Precipitators are uniformly used.
Energy Systems Research Laboratory, FIU
g p y
– Scrubbers are used to remove sulfur dioxide, which was implicated in creating acid rain.
– Low NOx burners are used to remove nitrogen oxides (Nox).
– CO2 removal is more difficult, with sequestration an option
Growth in Coal Generation: US and China
Energy Systems Research Laboratory, FIUSource http://www.netl.doe.gov/coal/refshelf/ncp.pdf
Background on the Electric Utility Industry
• First real practical uses of electricity began with the telegraph (around the civil war) and then arc lighting in the 1870’s (Broadway, the “Great White Way”).
• Central stations for lighting began with Edison in 1882, using a dc system (safety was key) but transitioned to ac
Energy Systems Research Laboratory, FIU
using a dc system (safety was key), but transitioned to ac within several years. Chicago World’s fair in 1893 was key demonstration of electricity
• High voltage ac started being used in the 1890’s with the Niagara power plant transferring electricity to Buffalo; also 30kV line in Germany
• Frequency standardized in the 1930’s
Regulation and Large Utilities
• Electric usage spread rapidly, particularly in urban areas. Samuel Insull (originally Edison’s secretary, but later from Chicago) played a major role in the development of large electric utilities and their holding companies
– Insull was also instrumental in start of state regulation in 1890’s
Energy Systems Research Laboratory, FIU
• Public Utilities Holding Company Act (PUHCA) of 1935 essentially broke up inter-state holding companies
– This gave rise to electric utilities that only operated in one state
– PUHCA was repealed in 2005
• For most of the last century electric utilities operated as vertical monopolies
Vertical Monopolies
• Within a particular geographic market, the electric utility had an exclusive franchise
Generation In return for this exclusivefranchise, the utility had the
Energy Systems Research Laboratory, FIU
Transmission
Distribution
Customer Service
yobligation to serve all existing and future customersat rates determined jointlyby utility and regulators
It was a “cost plus” business
9/13/2011
2
Vertical Monopolies
• Within its service territory each utility was the only game in town
• Neighboring utilities functioned more as colleagues than competitors
Energy Systems Research Laboratory, FIU
• Utilities gradually interconnected their systems so by 1970 transmission lines crisscrossed North America, with voltages up to 765 kV
• Economies of scale keep resulted in decreasing rates, so most every one was happy
History, cont’d -- 1970’s
• 1970’s brought inflation, increased fossil-fuel prices, calls for conservation and growing environmental concerns
• Increasing rates replaced decreasing ones
• As a result U S Congress passed Public Utilities
Energy Systems Research Laboratory, FIU
• As a result, U.S. Congress passed Public Utilities Regulator Policies Act (PURPA) in 1978, which mandated utilities must purchase power from independent generators located in their service territory (modified 2005)
• PURPA introduced some competition, but its implementation varied greatly by state
PURPA and Renewable Energy
• PURPA, through favorable contracts, caused the growth of a large amount of renewable energy in the 1980’s (about 12,000 MW of wind, geothermal, small scale hydro, biomass, and solar thermal)
Th k “ lif i f iliti ” (QF )
Energy Systems Research Laboratory, FIU
– These were known as “qualifying facilities” (QFs)
– California added about 6000 MW of QF capacity during the 1980’s, including 1600 MW of wind, 2700 MW of geothermal, and 1200 MW of biomass
– By the 1990’s the ten-year QFs contracts written at rates of $60/MWh in 1980’s, and they were no longer profitable at the $30/MWh 1990 values so many sites were retired or abandoned
Electricity Prices, 1990-2007
Source: EIA, annual energy review, 2007
Energy Systems Research Laboratory, FIU
Total USA solar/pv energy production was essentially flat from 1990 to 2005 (0.06 quad vs. 0.065)
Total wind generation stayed flat during 1990’s (around 0.03) but is now growing (0.32 in 2007; solar/pv is 0.08 in 2007)
History, cont’d – 1990’s & 2000’s• Major opening of industry to competition occurred
as a result of National Energy Policy Act of 1992
• This act mandated that utilities provide “nondiscriminatory” access to the high voltage transmission
Energy Systems Research Laboratory, FIU
• Goal was to set up true competition in generation
• Result over the last few years has been a dramatic restructuring of electric utility industry (for better or worse!)
• Energy Bill 2005 repealed PUHCA; modified PURPA
State Variation in Electric Rates
Energy Systems Research Laboratory, FIU
9/13/2011
3
Historical Electricity Use
Energy Systems Research Laboratory, FIU
Source: EIA, annual energy review, 2008
• Total USA solar/pv energy production was essentially flat from 1990 to 2005 (0.06 quad vs. 0.065)
• Total wind generation stayed flat during 1990’s (around 0.03) but is now growing (0.32 in 2007; solar/pv is 0.08 in 2007)
• In 2008, largest sources of renewable energy in descending order: hydroelectric, wood, biofuels, wind, waste, geothermal, solar/PV
http://www.eia.doe.gov/aer/pdf/aer.pdf
Historical Electricity Generation
Energy Systems Research Laboratory, FIU
• In 2008, fossil fuels (coal, petroleum, and natural gas) accounted for 71% of all net generation
• Nuclear contributed 20%• Renewable energy resources contributed 9% • In 2008, 67% of the renewable energy came from conventional
hydroelectric powerSource: EIA, annual energy review, 2008
The California-Enron Effect
RI
WA
OR
NV
CA
ID
MT
WY
UT CO KS
NE
SD
NDMN
IA
WI
MO
IL IN OH
KY
WVA VA
PA
NY
VT ME
MI
NHMA
CTNJ
DEMD
DC
Energy Systems Research Laboratory, FIU
Source : http://www.eia.doe.gov/cneaf/electricity/chg_str/regmap.html
AK
electricityrestructuring
delayedrestructurin
g
no activity suspendedrestructuring
CA
AZNM
TX
OK
MO KYTN
MS
LA
AL GA
FL
SCNC
AR
HI
August 14th, 2003 Blackout
Energy Systems Research Laboratory, FIU
https://reports.energy.gov/
Read the blackout report:
Renewable Portfolio Standards (September 2009)
WA: 15% by 2020*
CA: 20% by 2010
☼ NV: 25% by 2025*
UT: 20% by 2025*
☼ CO: 20% by 2020 (IOUs)10% by 2020 (co-ops & large munis)*
MT: 15% by 2015
ND: 10% by 2015
SD: 10% by 2015
IA: 105 MW
MN: 25% by 2025(Xcel: 30% by 2020)
☼ MO: 15% b 2021
WI: Varies by utility; 10% by 2015 goal
MI: 10% + 1,100 MW by 2015*
☼ OH: 25% by 2025†
ME: 30% by 2000New RE: 10% by 2017
☼ NH: 23.8% by 2025
☼ MA: 15% by 2020+ 1% annual increase(Class I Renewables)
RI: 16% by 2020
CT: 23% by 2020
☼ NY: 24% by 2013
☼ NJ: 22.5% by 2021
☼ PA: 18% by 2020†
☼ MD: 20% by 2022
VA: 15% by 2025*
VT: (1) RE meets any increase in retail sales by 2012;
(2) 20% RE & CHP by 2017
KS: 20% by 2020
☼ OR: 25% by 2025 (large utilities)*5% - 10% by 2025 (smaller utilities)
☼ IL: 25% by 2025
Energy Systems Research Laboratory, FIU
Source: http://www.dsireusa.org/
State renewable portfolio standard
State renewable portfolio goal
Solar water heating eligible *† Extra credit for solar or customer-sited renewables
Includes separate tier of non-renewable alternative resources
☼ AZ: 15% by 2025
☼ NM: 20% by 2020 (IOUs)10% by 2020 (co-ops)
HI: 40% by 2030
☼ Minimum solar or customer-sited requirement
TX: 5,880 MW by 2015
☼ MO: 15% by 2021☼ y
☼ DE: 20% by 2019*
☼ DC: 20% by 2020☼ NC: 12.5% by 2021 (IOUs)
10% by 2018 (co-ops & munis)
29 states & DChave an RPS
5 states have goals
Impact of 2009 Stimulus Bill on Renewable Energy
• American Recovery and Reinvestment Act (ARRA)
• The 2009 stimulus bill contained several provisions related to renewable energy– $32 billion to enhance the electric power grid
Energy Systems Research Laboratory, FIU
– A three year extension to renewable production tax credits
– About $40 billion for energy efficiency in various forms
– $2 billion for advanced battery manufacturing
• Also a lot of synchrophasor-related ARRA projects– http://www.naspi.org/meetings/workgroup/workgroup.stm
– Synchrophasors and renewable energy integration are related
9/13/2011
4
Power System Structure
• All power systems have three major components: Load, Generation, and Transmission/Distribution.
• Load: Consumes electric power
• Generation: Creates electric power.
Energy Systems Research Laboratory, FIU
• Transmission/Distribution: Transmits electric power from generation to load.
• A key constraint is since electricity can’t be effectively stored, at any moment in time the net generation must equal the net load plus losses
2007 USA Electric Energy FlowNote, Electricity is “Refined” Energy
Energy Systems Research Laboratory, FIU
Source: EIA 2007 Annual Energy Review
2008 USA Electric Energy Flow
Energy Systems Research Laboratory, FIU
Source: EIA 2008 Annual Energy ReviewNote- this graphic does NOT show losses
LOADS
• Can range in size from less than one watt to 10’s of MW
• Loads are usually aggregated for system analysis
• The aggregate load changes with time, with strong
Energy Systems Research Laboratory, FIU
gg g g gdaily, weekly and seasonal cycles
– Load variation is very location dependent
Loads- Household Consumption
Source: EIA 2008 Annual Energy Review
Energy Systems Research Laboratory, FIU
Example: Daily Variation for CA
Energy Systems Research Laboratory, FIU
9/13/2011
5
Example: Weekly Variation
Energy Systems Research Laboratory, FIU
Change in US Electric Demand Growth
Energy Systems Research Laboratory, FIU
Source: EIA Annual Energy Outlook 2010
Example: Annual System Load
15000
20000
25000
W L
oad
Energy Systems Research Laboratory, FIU
0
5000
10000
1
518
1035
1552
2069
2586
3103
3620
4137
4654
5171
5688
6205
6722
7239
7756
8273
Hour of Year
MW
Load Duration Curve
• A very common way of representing the annual load is to sort the one hour values, from highest to lowest. This representation is known as a “load duration curve.”
6000
5000
Energy Systems Research Laboratory, FIU
4000
3000
2000
1000
0
DEM
AN
D (M
W)
0 1000 HRS 7000 8760
Load duration curve tells how much generation is needed
GENERATION
• Large plants predominate, with sizes up to about 1500 MW.
• Coal is most common source (56%), followed by nuclear (21%), hydro (10%) and gas
Energy Systems Research Laboratory, FIU
(10%).
• New construction is mostly natural gas, with economics highly dependent upon the gas price
• Generated at about 20 kV for large plants
New Generation by Fuel Type(USA 1990 to 2030, GW)
Energy Systems Research Laboratory, FIU
Source: EIA Annual Energy Outlook 2007
9/13/2011
6
Basic Gas Turbine Efficiency
Compressor
Fuel100%
Combustion chamber
Turbine Generator
ACPower 33%
1150 oC
Energy Systems Research Laboratory, FIU
Fresh air
Exhaustgases 67%
550 oC
Brayton Cycle: Working fluid is always a gas
Most common fuel is natural gas
Maximum Efficiency
550 2731 42%
1150 273
Typical efficiency is around 30 to 35%
Gas Turbine
Energy Systems Research Laboratory, FIU
Source: Masters
Combined Heat and Power
Compressor
Fuel100%
Combustion chamber
Turbine
Exhaust gases
Generator
ACPower 33%
Energy Systems Research Laboratory, FIU
Fresh air
Heat recovery steamgenerator (HRSG)
Water pump
Feedwater
Exhaust 14%
Steam 53%
Process heat
Absorption cooling
Space & water heating
Overall Thermal Efficiency = 33% (Electricity) + 53% (Heat) = 86%
Combined Cycle Power Plants
Energy Systems Research Laboratory, FIU
Efficiencies of up to 60% can be achieved, with even higher values when the steam is used for heating
Determining operating costs• In determining whether to build a plant, both the fixed
costs and the operating (variable) costs need to be considered.
• Once a plant is build, then the decision of whether or not to operate the plant depends only upon the variable costs
Energy Systems Research Laboratory, FIU
• Variable costs are often broken down into the fuel costs and the O&M costs (operations and maintenance)
• Fuel costs are usually specified as a fuel cost, in $/Mbtu, times the heat rate, in MBtu/MWh– Heat rate = 3.412 MBtu/MWh/efficiency
– Example, a 33% efficient plant has a heat rate of 10.24
Heat Rate
• Fuel costs are usually specified as a fuel cost, in $/Mbtu, times the heat rate, in MBtu/MWh
– Heat rate = 3.412 MBtu/MWh/efficiency
– Example, a 33% efficient plant has a heat rate of 10 24 Mbtu/MWh
Energy Systems Research Laboratory, FIU
10.24 Mbtu/MWh
– About 1055 Joules = 1 Btu
– 3600 kJ in a kWh
• The heat rate is an average value that can change as the output of a power plant varies.
• Do Example 3.5, material balance
9/13/2011
7
Historical and Forecasted Heat Rates
Energy Systems Research Laboratory, FIU
http://www.npc.org/Study_Topic_Papers/4-DTG-ElectricEfficiency.pdf
Fixed Charge Rate (FCR)
• The capital costs for a power plant can be annualized by multiplying the total amount by a value known as the fixed charge rate (FCR)
• The FCR accounts for fixed costs such as interest on loans, returns to investors, fixed operation and
Energy Systems Research Laboratory, FIU
, , pmaintenance costs, and taxes.
• The FCR varies with interest rates, and is now below 10%.
• For comparison this value is often expressed as$/yr-kW
Annualized Operating Costs
• The operating costs can also be annualized by including the number of hours a plant is actually operated
• Assuming full output the value is
Energy Systems Research Laboratory, FIU
Variable ($/yr-kW) =
[Fuel($/Btu) * Heat rate (Btu/kWh) +
O&M($/Kwh)]*(operating hours/hours in year)
Coal Plant Example
• Assume capital costs of $4 billion for a 1600 MW coal plant with a FCR of 10% and operation time of 8000 hours per year. Assume a heat rate of 10 Mbtu/MWh, fuel costs of 1.5 $/Mbtu, and variable O&M of $4.3/MWh. What is annualized cost per kWh?
Energy Systems Research Laboratory, FIU
Fixed Cost($/kW) = $4 billion/1.6 million kW=2500 $/kWAnnualized capital cost = $250/kW-yr
Annualized operating cost = (1.5*10+4.3)*8000/1000
= $154.4/kW-yr
Cost = $(250 + 154.4)/kW-yr/(8000h/yr) = $0.051/kWh
Capacity Factor (CF)
• The term capacity factor (CF) is used to provide a measure of how much energy a plant actually produces compared to the amount assuming it ran at rated capacity for the entire year
Energy Systems Research Laboratory, FIU
CF = Actual yearly energy output/(Rated Power * 8760)
• The CF varies widely between generation technologies,
Generator Capacity Factors
Energy Systems Research Laboratory, FIUSource: EIA Electric Power Annual, 2007
The capacity factor for solar is usually less than 25% (sometimes substantially less), while for wind it is usually between 20 to 40%). A lower capacity factor means a higher cost per kWh
9/13/2011
8
One-line Diagrams
• Most power systems are balanced three phase systems.
• A balanced three phase system can be modeled as a single (or one) line.
Energy Systems Research Laboratory, FIU
• One-lines show the major power system components, such as generators, loads, transmission lines.
• Components join together at a bus.
PowerWorld Simulator Three Bus System
Bus 2 Bus 1
204 MW
102 MVR
150 MW116 MVR
1.00 PU
-20 MW 4 MVR
20 MW -4 MVR
-34 MW10 MVR
-14 MW
4 MVR
1.00 PU
106 MW 0 MVR
100 MWAGC ONAVR ON
Load withgreenarrows indicatingamountof MWflow
Note the
Energy Systems Research Laboratory, FIU
Bus 3Home Area
150 MW 37 MVR
116 MVR
102 MW 51 MVR
34 MW-10 MVR
14 MW -4 MVR
1.00 PU
AVR ON
AGC ONAVR ON
flow
Usedto controloutput ofgenerator Direction of arrow is used to indicate
direction of real power (MW) flow
power balance ateach bus
Power Balance Constraints
• Power flow refers to how the power is moving through the system.
• At all times in the simulation the total power flowing into any bus MUST be zero!
Energy Systems Research Laboratory, FIU
flowing into any bus MUST be zero!
• This is know as Kirchhoff’s law. And it can not be repealed or modified.
• Power is lost in the transmission system.
Basic Power Flow Control
• Opening a circuit breaker causes the power flow to instantaneously (nearly) change.
• No other way to directly control power flow in a transmission line
Energy Systems Research Laboratory, FIU
in a transmission line.
• By changing generation we can indirectly change this flow.
Transmission Line Limits
• Power flow in transmission line is limited by heating considerations.
• Losses (I2 R) can heat up the line, causing it to sag
Energy Systems Research Laboratory, FIU
to sag.
• Each line has a limit; Simulator does not allow you to continually exceed this limit. Many utilities use winter/summer limits.
Overloaded Transmission Line
Energy Systems Research Laboratory, FIU
9/13/2011
9
Interconnected Operation
• Power systems are interconnected. Most of North America east of the Rockies is one system, with most of Texas and Quebec being exceptions
I i di id d i ll
Energy Systems Research Laboratory, FIU
• Interconnections are divided into smaller portions, called balancing authority areas (previously called control areas)
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.
Energy Systems Research Laboratory, FIU
• The flow out of an area is equal to
total gen - total load - total losses
= tie-flow
Area Control Error (ACE)• The area control error is the difference
between the actual flow out of an area, and the scheduled flow.
• Ideally the ACE should always be zero.
B h l d i l h i h
Energy Systems Research Laboratory, FIU
• Because the load is constantly changing, each utility must constantly change its generation to “chase” the ACE.
Automatic Generation Control• BAs use automatic generation control (AGC)
to automatically change their generation to keep their ACE close to zero.
• Usually the BA control center calculates ACE b d ti li fl th th AGC
Energy Systems Research Laboratory, FIU
based upon tie-line flows; then the AGC module sends control signals out to the generators every couple seconds.
Three Bus Case on AGC
Bus 2 Bus 1
266 MW
133 MVR1.00 PU
-40 MW 8 MVR
40 MW -8 MVR
1.00 PU
101 MW5 MVR
Energy Systems Research Laboratory, FIU
Bus 3Home Area
150 MW
250 MW 34 MVR
166 MVR
133 MW 67 MVR
-77 MW 25 MVR
78 MW-21 MVR
39 MW-11 MVR
-39 MW
12 MVR
1.00 PU
5 MVR
100 MWAGC ONAVR ON
AGC ONAVR ON
Generator Costs• There are many fixed and variable costs
associated with power system operation.
• The major variable cost is associated with generation.
C t t t MWh id l
Energy Systems Research Laboratory, FIU
• Cost to generate a MWh can vary widely.
• For some types of units (such as hydro and nuclear) it is difficult to quantify.
• Many markets have moved from cost-based to price-based generator costs
9/13/2011
10
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.
Energy Systems Research Laboratory, FIU
IC1(PG,1) = IC2(PG,2) = … = ICm(PG,m)
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.
Energy Systems Research Laboratory, FIU
• Scheduled power transactions are implemented by modifying the area ACE:
ACE = Pactual,tie-flow - Psched
100 MW Transaction
Bus 2 Bus 1
225 MW
113 MVR
150 MW
1.00 PU
8 MW -2 MVR
-8 MW 2 MVR
-84 MW -92 MW
1.00 PU
0 MW 32 MVR
AGC ON
Energy Systems Research Laboratory, FIU
Bus 3Home Area
Scheduled Transactions
150 MW
291 MW 8 MVR
138 MVR
113 MW 56 MVR
27 MVR
85 MW-23 MVR
93 MW-25 MVR
30 MVR
1.00 PU
100 MWAGC ONAVR ON
AGC ONAVR ON
100.0 MW
Scheduled 100 MW Transaction from Left to Right
Net tie-line flow is now 100 MW
Security Constrained Economic Dispatch
• Transmission constraints often limit system economics.
• Such limits required a constrained dispatch in order to maintain system security
Energy Systems Research Laboratory, FIU
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.
Security Constrained Dispatch
Bus 2 Bus 1
357 MW
179 MVR
194 MW
1.00 PU
-22 MW 4 MVR
22 MW -4 MVR
-142 MW -122 MW
1.00 PU
0 MW 37 MVR100%
OFF AGC
Energy Systems Research Laboratory, FIU
Bus 3Home Area
Scheduled Transactions
448 MW 19 MVR
232 MVR
179 MW 89 MVR
49 MVR
145 MW-37 MVR
124 MW-33 MVR
41 MVR
1.00 PU
100%
100 MWAVR 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
Multiple 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
Energy Systems Research Laboratory, FIU
• 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.”
9/13/2011
11
Seven Bus Case One-line Diagram
Top Area Cost
1
2
3 4
5
106 MW 110 MW 40 MVR
80 MW 30 MVR
1.00 PU
1.01 PU1.04 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
94 MW
AGC ON
AGC ONCase Hourly Cost 16933 $/MWH
System hasthree areas
Area top has fivebuses
Energy Systems Research Laboratory, FIU
p
Left Area Cost Right Area Cost
2 5
6 7
168 MW
200 MW 201 MW
130 MW 40 MVR
40 MW 20 MVR
1.04 PU1.04 PU
-39 MW
40 MW-20 MW 20 MW
40 MW
-40 MW
200 MW 0 MVR
200 MW 0 MVR
20 MW -20 MW
AGC ON
AGC ON
AGC ON
8029 $/MWH
4715 $/MWH 4189 $/MWH
Area left has one bus
Area right has one bus
Seven Bus Case: Area ViewArea Losses
Top
-40.1 MW
0.0 MW 0.0 MW 40.1 MW
7.09 MW
Actualflowbetweenareas
System has40 MW f
Energy Systems Research Laboratory, FIU
Area Losses Area Losses
Left Right
0.0 MW 40.1 MW
0.33 MW 0.65 MW
Loop flow can result in higher losses
40 MW of“Loop Flow”
Scheduledflow
Seven Bus System – Loop Flow?Area Losses
Top
-4.8 MW
0.0 MW 0.0 MW 4.8 MW
9.44 MW
Note thatTop’s Losses haveincreasedf
Transaction has actually decreasedthe loop flow
Energy Systems Research Laboratory, FIU
Area Losses Area Losses
Left Right
100.0 MW 104.8 MW
-0.00 MW 4.34 MW
100 MW Transactionbetween Left and Right
from 7.09MW to9.44 MW
Power Transfer Distribution Factors (PTDFs)
• PTDFs are used to show how a particular transaction will affect the system.
• Power transfers through the system according
Energy Systems Research Laboratory, FIU
to the impedances of the lines, without respect to ownership.
• All transmission players in network could be impacted, to a greater or lesser extent.
17%
58% 41%
51% 42%
34%
A B
C
D
400.0 MWMW 400.0 MWMW 300.0 MWMW
250.0 MWMW
PTDF Example: Nine Bus System Actual Flows
Energy Systems Research Laboratory, FIU
45% 6%
54%
29%
32%
G E
I
F
H
250.0 MWMW
200.0 MWMW
250.0 MWMW
150.0 MWMW
50.0 MW
39%
44%
56% 13%
30% 20%
10%
A B
C
D
400.0 MWMW 400.0 MWMW 300.0 MWMW
250.0 MWMW
PTDF Example: PTDFs for Transfer from A to I
Energy Systems Research Laboratory, FIU
35% 2%
34%
34%
32%
G E
I
F
H
250.0 MWMW
200.0 MWMW
250.0 MWMW
150.0 MWMW
50.0 MW
34%
9/13/2011
12
PTDF Example: PTDFs for Transfer from G to F
6%
6% 12%
18%
61%
12%
6%
A B
C
D
400.0 MWMW 400.0 MWMW 300.0 MWMW
250.0 MWMW
Energy Systems Research Laboratory, FIU
61% 19%
21%
21%
G E
I
F
H
250.0 MWMW
200.0 MWMW
250.0 MWMW
150.0 MWMW
50.0 MW
20%
Role of RTO/ISO and NERC Reliability Coordinators
Energy Systems Research Laboratory, FIU
Photo source: http://www.ferc.gov/industries/electric/indus-act/rto/rto-map.asp
Pricing Electricity
• Cost to supply electricity to bus is called the location marginal price (LMP)
• Presently PJM and MISO post LMPs on the web
• In an ideal electricity market with no transmission limitations the LMPs are equal
Energy Systems Research Laboratory, FIU
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)
Three Bus Case LMPs: Line Limit NOT Enforced
Bus 2 Bus 1
0 MW 10.00 $/MWh
60 MW 60 MW
120 MW
10.00 $/MWh
180 MW120%
Gen 1’s costis $10 per MWh
Gen 2’s costis $12 per MWh
Energy Systems Research Laboratory, FIU
Bus 3
Total Cost
0 MW
180 MWMW
60 MW
60 MW120 MW
10.00 $/MWh
120%
0 MWMW
1800 $/hr
Line from Bus 1 to Bus 3 is over-loaded; all buses have same marginal cost
Three Bus Case LMPS: Line Limits Enforced
Bus 2 Bus 1
60 MW 12.00 $/MWh
20 MW 20 MW
100 MW
10.00 $/MWh
120 MW100%
Energy Systems Research Laboratory, FIU
Bus 3
Total Cost
0 MW
180 MWMW
80 MW
80 MW100 MW
14.01 $/MWh
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 $14 / MWh
Generation Supply Curve
40
60
80
/ M
Wh)
Base LoadCoal and Nuclear
NaturalGas Generation
As the load goes up so does the price
Energy Systems Research Laboratory, FIU
0
20
40
0 10000 20000 30000 40000
Generation (MW)
Pri
ce ($ Coal and Nuclear
Generation
Renewable Sources Such as Wind Have Low Marginal Cost, but they are Intermittent
9/13/2011
13
MISO LMPs on Sept 21, 2010 (7:50am)
Energy Systems Research Laboratory, FIU
Available on-line at www.midwestmarket.org
MISO LMPs on Sept 21, 2010 (7:50am)
Energy Systems Research Laboratory, FIU
Frequency Control
• Steady-state operation only occurs when the total generation exactly matches the total load plus the total losses– too much generation causes the system frequency
Energy Systems Research Laboratory, FIU
too much generation causes the system frequency to increase
– too little generation causes the system frequency to decrease (e.g., loss of a generator)
• AGC is used to control system frequency
April 23, 2002 Frequency Response Following Loss of 2600 MW
Energy Systems Research Laboratory, FIU