ECEN 460
Power System Operation & Control
2022 SPRING
DR. WON JANG
Motivation
 In 2000, the US National Academy of Engineering (NAE) named
Electrification as the greatest engineering achievements of the 20th century
o After electrification:
automobiles (2), airplanes (3),
water system (4), electronics (5)
 Electricity has changed the world!
 For the 21st century, the winner
could be “Development of a
sustainable and resilient electric
infrastructure for the entire world”?
o What’s your guess?
http://www.greatachievements.org/
Power System Components
 Generation
o Source of power
o Ideally with a specified voltage and frequency
 Load
o Consumes power
o Ideally with a constant resistive value
 Transmission system
o Transmits power
o Ideally as a perfect conductor
https://www.energy.gov/sites/prod/files/2017/02/f34/Quadrennial%20Energy%20Review--Second%20Installment%20%28Full%20Report%29.pdf
https://www.energy.gov/sites/prod/files/2017/02/f34/Quadrennial%20Energy%20Review--Second%20Installment%20%28Full%20Report%29.pdf
Complications
 No ideal voltage sources exist
 Loads are seldom constant
 Transmission system has resistance, inductance, capacitance and flow
limitations
 Simple system has no redundancy so power system will not work if any
component fails
Power System Examples
 Electric utilities range from quite small, such as an island, to one covering
half the continent
 Four major interconnected AC power systems in North American, each
operating at 60 Hz ac; 50 Hz is used in some other countries.
 Microgrids can power smaller areas (like a campus) and can be optionally
connected to the main grid
 Airplanes and Spaceships: reduction in weight is primary consideration;
frequency is 400 Hz.
 And more: Ships, submarines, automobiles, battery operated portable
systems
North America Interconnections
 4 NA interconnections
 8 North American Electric Reliability Corporation (NERC) reliability
regions
Electricity System Overview by DOE 2017
Source: www.puc.texas.gov/industry/maps/maps/ERCOT.pdf
Electric Systems in Energy Context
 Class focuses on electric power systems, but we first need to put the
electric system in context of the total energy delivery system
 Electricity is used primarily as a means for energy transportation
 About 40% of US energy is transported in electric form
 Concerns about need to reduce CO2
emissions and fossil fuel depletion are
becoming main drivers for change
in world energy infrastructure
https://flowcharts.llnl.gov/content/assets/images/energy/us/Energy_US_2017.png
https://sdgs.un.org/news/un-secretary-general-issues-roadmap-clean-energy-all-2030-33361
https://www.washingtonpost.com/world/2021/11/10/15c-2c-climate-temperature-targets-cop26/
Bipartisan Infrastructure Bill
 Deliver clean water to all American families
 Ensure every American has access to reliable high-speed internet
 Repair and rebuild our roads and bridges with a focus on climate
change mitigation, resilience, equity, and safety for all users
 Improve transportation options and reduce greenhouse
emissions
 Upgrade our nation’s airports and ports to strengthen our
supply chains and prevent disruptions that have caused inflation
 Make the largest investment in passenger rail
 Build a national network of electric vehicle (EV) chargers
 Upgrade our power infrastructure to deliver clean, reliable
energy across the country and deploy cutting-edge energy
technology to achieve a zero-emissions future
 Make our infrastructure resilient against the impacts of climate
change, cyber-attacks, and extreme weather events
 Deliver the largest investment in tackling legacy pollution
Global Energy Consumption by Source
https://ourworldindata.org/energy-mix
Historical Perspective: Summary
 Early 1900s saw increasing electricity usage and development of large
utilities companies
 The 1970s were riddled with inflation and environmental concerns as well
as introduction of competition (to some extent)
 Dramatic restructuring took place in 1990s/2000s, with many states
adopting competitive markets and “open access transmission” policy
 Current efforts have been focused on smart and clean electricity
History of Electric Power
 First real practical uses of electricity began with the telegraph (1860's) and
then arc lighting in the 1870’s
 Early 1880’s – Edison introduced Pearl Street dc system in Manhattan
supplying 59 customers
 1884 – Sprague produces practical dc motor
 1885 – Invention of transformer
 Mid 1880’s – Westinghouse/Tesla introduce rival ac system
 Late 1880’s – Tesla invents ac induction motor
 Chicago World’s fair in 1893 was key demonstration of electricity
 1893 – Three-phase transmission line at 2.3 kV
History of Electric Power
 1896 – ac lines deliver electricity from hydro generation at Niagara Falls to
Buffalo, 20 miles away; also 30kV line in Germany
 Early 1900’s – Private utilities supply all customers in area (city); recognized
as a natural monopoly; states step in to begin regulation
 By 1920’s – Large interstate holding companies control most electricity
systems
 1935 – Congress passes Public Utility Holding Company Act (PUHCA) to
establish national regulation, breaking up large interstate utilities (repealed
2005)
 1935/6 – Rural Electrification Act brought electricity to rural areas
 1930’s – Electric utilities established as vertical monopolies
 Frequency standardized in the 1930’s
History of Electric Power - 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 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
History of Electric Power - 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
 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
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
o Insull was also instrumental in start of state regulation in 1890’s
 Public Utilities Holding Company Act (PUHCA) of 1935 essentially
broke up inter-state holding companies
o This gave rise to electric utilities that only operated in one state
o PUHCA was repealed in 2005
 For most of the last century electric utilities operated as vertical
monopolies
Utility Restructuring
 Driven by significant regional variations in electric rates
 Goal of competition is to reduce rates through the introduction of
competition
 Eventual goal is to allow consumers to choose their electricity supplier
Vertically integration
Deregulation
Generation
Transmission
Distribution
Distribution
Customer Service
utilities had an
“obligation to serve”
“obligation to serve”
is now a market function
The Goal: Customer Choice
Electricity rates comparison in Champaign, IL
State Variation in Electric Rates
https://www.globalenergyinstitute.org/average-electricity-retail-prices-map
Prices Change with Location …
https://www.ercot.com/content/cdr/contours/rtmLmpHg.html
… and Time
 Click the link below for the current price in ERCOT
o https://www.ercot.com/content/cdr/contours/rtmLmpHg.html
Supply Demand Patterns
The BEFORE scenario
MW
thermal generation
The CURRENT scenario
MW
load
thermal
load
time
Additional generation
capacity maintained as
reserves
wind
time
Renewable generation
patterns are harder to
understand
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 daily, weekly and
seasonal cycles
o Load variation is very location dependent
Weekly/hourly Load Variation
https://www.eia.gov/todayinenergy/detail.php?id=42915
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
DEMAND (MW)
5000
4000
3000
2000
1000
0
0
1000
HRS
7000
8760
 Load duration curve tells how much generation is needed
Monitoring is Crucial!
 Large and complex hardware-software systems are used for real-time
operations and control
o Energy management system (EMS)
o Supervisory control and data acquisition (SCADA)
 Frequency is closely monitored and maintained around 60 Hz
o Area control error (ACE) is measure for frequency excursions as well as deviations
from scheduled interchanges – ideally, it should be zero
o Automatic generation control (AGC) implements PID control to keep ACE = zero
Operation and Control
 Economics and reliability are the key drivers in power system operations
and control
 Economics leads to large optimization problems for
o Resource scheduling via unit commitment
o Least-cost dispatch of available generation
 Reliability requirements typically entail no violations of physical limits and
voltages and frequencies within prescribed bounds
o Continuous monitoring
o Hierarchical control architecture
Sequence of Operations
area
control
error
ON/OFF
decision
dispatch
signal
unit
commitment: MIP
economic
dispatch:
SCOPF
dayahead
forecast
minutesahead
forecast
days
minutes
reference
set-point
automatic
generation
control
real-time
grid
dynamics
realtime
data
seconds
time scale for operations
real-time
Frequency Regulation
Evolution of system frequency following loss of 2600 MW of generation
California electricity crisis in 2000/2001
August 14th, 2003 Blackout
The Smart Grid
 The term “Smart Grid” dates officially to the 2007 “Energy Independence
and Security Act”, Title 13 (“Smart Grid”)
o Use of digital information and control techniques
o Dynamic grid optimization with cyber-security
o Deployment of distributed resources including
o Customer participation and smart appliances
o Integration of storage including PHEVs
o Development of interoperability standards