1. ECE 333 Green Energy Systems
Lecture 6: Power System History and Operations
Dr. Karl Reinhard
Dept. of Electrical and Computer Engineering
University of Illinois at Urbana-Champaign

2. Announcements Be reading Chapter 3 Quiz today on Hmwk 2
Homework 3 posted
Quiz on Thursday Feb 8
Material from Power Systems history and operations will be covered on exams
Short answer or true/false
Drawn from homework questions

3. To Know: Power Systems History
T. Edison and G. Westinghouse advocated AC and DC power systems respectively. Outline their reasoning (pros and cons for each). Why did AC become the standard?
What was Samuel Insull's electric power industry insight and how did it lead to public utility commissions?
What led to the PUHCA of 1935 and what was the Act's aim?
What led to the PURPA of 1978? What were the Act's two key provisions? How did the Act impact the renewable energy industry?
What were the major provisions of the EPAct of 1992?
What was the main thrust common to PURPA and EPAct?
What were the main provisions of EISA of 2007 ?

4. To Know: Power Systems Operation
What legislation institutionalized the term “Smart Grid?” What were the major objectives / provisions relating to “Smart Grid”
Outline the concept of balancing energy supply and demand. Describe normal load fluctuations and the affect that energy imbalances have on system frequency.
Explain the roles that "must run – baseload", "load- following","peakers", “reserves”, and "re-newable" power plants have in the power system. Give examples of each.
What role does "demand response" play?
Describe how grid instabilities occur.

5. History – Early Utilities
First practical electricity uses began with the telegraph (~ Civil War) and then arc lighting in the 1870’s (Broadway, the “Great White Way”).
Central stations for lighting began in 1882 – dc (Edison) system, but stations transitioned to ac (Westinghouse) within several years.
Chicago 1893 World’s fair had an important early electricity demonstration
High voltage ac appeared in the 1890’s w/ the Niagara power plant transferring electricity to Buffalo; also 30kV line in Germany
Frequency standardization in the 1930’s

6. History – Large Utilities & Regulation
Electric usage spread rapidly, particularly in urban areas.
Samuel Insull (had served as Edison’s secretary) played a major role in the development of large electric utilities and their holding companies
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 20th Century electric utilities operated as vertical monopolies

7. History – Vertical Monopolies
Within a particular geographic market, the electric utility had an exclusive franchise
Generation
Transmission
Distribution
Customer Service
In return for this exclusive franchise, the utility had the obligation to serve all
existing and future customers at rates determined jointly by utility and regulators
It was a “cost plus” business 6

8. History – Vertical Monopolies (cont)
Within its service territory each utility was the only game in town
Neighboring utilities functioned as colleagues (rather than competitors)
Utilities gradually interconnected their systems so by transmission lines crisscrossed North America, with voltages up to 765 kV
Economies of scale reduced electricity rates, so most were happy… but all good things come to an end
Customers could not have on-site generation and remain connected to the utility 7

9. History – Utilities 1970’s
1970’s brought inflation, increased fossil-fuel prices, supply shortfalls (Arab oil embargo), calls for conservation, and growing environmental concerns
 Electricity rates began to climb
U.S. Congress passed Public Utilities Regulator Policies Act (PURPA) in 1978, which mandated utilities purchase power from independent generators located in their service territory (modified 2005)
PURPA introduced competition, but implementation varied greatly state to state
Allowed customers to build on-site generation & be grid connected
Required Utilities to purchase from qualifying facilities (QFs)
Gave birth to the electric side of renewable energy industry 8

10. History – PURPA and Renewables
PURPA* enabled the significant small producer renewable energy production growth in the 80’s:
Req’d utilities to purchase from qualifying facilities (QF): < 80 MW and 75% renewable energy source wind, solar, geothermal, etc.
During the 1980’s, California added ~ 6000 MW of QF capacity : MW wind, 2700 MW geothermal, and 1200 MW biomass
In the 90’s, 10-year QFs contracts in 80’s) were no longer competitive $30/MWh in 90’s …  many sites were retired or abandoned
* Public Utilities Regulator Policies Act (PURPA) 1978

11. History – Abandoned PURPA Wind Farm – Hawaii
Source: Prof. Sanders

12. History – Electricity Prices, ‘60-2014
Source: EIA, Monthly Energy Review, accessed 30 Jan 18

13. History– 1990’s & 2000’s
Major opening of industry to competition occurred as a result of National Energy Policy Act of 1992 (EPAct of 92)
Goal was to set up true competition in generation
Mandated “nondiscriminatory” access to the Hi Volt transmission
Major electric power industry restructuring – breaking industry into 3 segments – Generators, Transmitters, Distributers
EPAct of 2005 repealed PUHCA; modified PURPA
Energy Independence and Securty Act of 2007 (EISA 2007) aimed to promote
the production of clean renewable fuels,
the efficiency of products, buildings, and vehicles,
research on and deployment of greenhouse gas capture and storage options 12

14. History – IL Energy Markets (’97-’07)
Two main electric utilities in Illinois are ComEd and Ameren
In ’97, vertically integrated & IL electricity rates in highest 10 among the states
In deregulated markets, utility owns the infrastructure & distributes power, but Alternate Retail Electricity Suppliers (ARES) buy it from the generators and sell it to customers.
In ’97, IL law changed – restructuring Electric Power industry – forcing competition; full implementation in ’07.
In 2014, there were 87 ARES operating in IL – IL power rates in were in lowest 10 among the states….. Avg $0.099 / kWh

15. State Electric Rate Variations 2017
accessed 30 Jan 18 14

16. Urbana Electric Rates 2018
, accessed 31 Jan 18 15

17. Illinois 2012: Municipal Aggregation
Urbana and Champaign residents started seeing substantially lower electric bills as a result of municipal aggregation
This was approved by a 2-1 margin in 3/2012 referendum
Municipal aggregation means all residents of a community get their electricity from a third party supplier chosen by the city (as opposed to the local utility) unless they specifically opt out.
They still get bills from Ameren, and do pay an electricity delivery charge (about 30 to 40% of total bill)
Recently Ameren rates have dropped, making third party options less attractive

18. U.S. Electricity Generation by Type
BkWh/Yr
4000
3000
2000
1000
Source: EIA
Accessed 31 Jan 18

19. The Rise of Renewables: Wind
Source: AWEA Wind Power Outlook 4th Qtr, accessed 31 Jan 18

20. U.S. PV Electricity Installed Capacity & Generation
Recent Growth in Solar
U.S. PV Electricity Installed Capacity & Generation
Source: DoE 2016 Renewable Energy Book
accessed 31 Jan 18

21. Recent Solar Installation Costs
NREL PV system cost 2010–2017summary
(inflation adjusted)
accessed 1/31/18

22. The Smart Grid
EISA 2007, Title 13 Introduced “Smart Grid” w/ key provisions:
Use of digital information and control techniques
Dynamic grid optimization with cyber-security
Deployment of distributed resources
Customer participation and smart appliances
Integration of storage including Plug-in Hybrid Electric Vehicles (PHEVs)
Interoperability standards development
accessed 31 Jan 18

23. Smart Grid Perceptions
(Some of Us Like the Term “Smarter”)

24. States Setting “Renewable Portfolio Standards”
Source: accessed 31 Jan 18

25. Power System Operations: 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.
One-lines show the major power system components, such as generators, loads, transmission lines.
Components join together at a bus. 24

26. Substation Bus 25

27. Power System Time Frames
Next few slides will consider the power flow (quasi-steady) time frame
Image source: P.W. Sauer, M.A. Pai, Power System Dynamics and Stability, 1997, Fig 1.2, modified

28. PowerWorld Simulator Three Bus System
Load with
green
arrows
indicating
amount
of MW
flow
Note the
power
balance at
each bus
Used
to control
output of
generator
Direction of arrow is used to indicate
direction of real power (MW) flow 27

29. Power Flow A common power system analysis tool is the power flow
It shows how real and reactive power flows through a network, from generators to loads
Solves sets of non-linear equations enforcing "conservation of power" at each bus in the system (a consequence of KCL)
Loads are usually assumed to be constant power
Used to determine if any transmission lines or transformers are overloaded and system voltages
Educational version PowerWorld tool available at

30. Metro Chicago Electric Network29

31. 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!
This is know as Kirchhoff’s law. And it can not be repealed or modified.
Power is lost in the transmission system. 30

32. 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!
This is know as Kirchhoff’s law. And it can not be repealed or modified.
Power is lost in the transmission system. 31

33. 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.
By changing generation we can indirectly change this flow. 32

34. Transmission Line Limits
Power flow in transmission line is limited by heating considerations.
Losses (I^2 R) can heat up the line, causing it to sag.
Each line has a limit; Simulator does not allow you to continually exceed this limit. Many utilities use winter/summer limits. 33

35. Overloaded Transmission Line34

36. 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
Interconnections are divided into smaller portions, called balancing authority areas (previously called control areas)
Balancing authorities sometimes correspond to a single utility, but increasingly they include a large number of utilities.
NERC Reliability Coordinators are charged with overseeing the reliable operation of the grid 35

37. NORTH AMERICAN INTERCONNECTIONS36

38. NERC Reliability Coordinators
Illinois is split, with the ComEd part in PJM, with the rest of the state in MISO
Source:

39. 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 38

40. North American Balancing Authorities
Source:

41. 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.
Because the load is constantly changing, each utility must constantly change its generation to “chase” the ACE.
MISO ACE| (in MW) from 9/19/12. At the time the MISO load was about 65GW 40

42. 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 based upon tie-line flows; then the AGC module sends control signals out to the generators every couple seconds. 41

43. Three Bus Case on AGC 42