Lecture 1 Introduction

Transcription

1 EE 333 POWER SYSTEMS ENGINEERING Lecture 1 Introduction Dr. Lei Wu Department of Electrical and Computer Engineering Clarkson University

2 About The Class Course meeting time: TuTh 2:30pm-3:45pm CAMP 178 Course website: Office hours: Tu/Th 9:30-11:30am or by appointment Office: CAMP 147 Phone:

3 About The Class (Cont d) Textbook: J.D. Glover, M.S. Sarma, and T. Overbye, Power System Analysis and Design, Fourth/Fifth Edition, Cengage Learning. References: A.R. Bergen and V. Vittal, Power System Analysis, Second Edition, Prentice Hall, Distributed notes and/or papers. 3

4 Homework For homework submission, staple all the pages and write your name and student ID on the first page. Homework is due before the class on the due date. Late homework will not be accpted. 4

5 Exams Students are expected to attend all exams. If you find you must miss an exam due to a legitimate conflict, a make-up will be given only under the following conditions: The student has informed the instructor of the absence at least 24 hours in advance of missing the exam. The student misses the exam due to some situation beyond the student s control (such as a serious illness, the family emergency, etc.), which is unexpected, unavoidable, and documented. The reason for each absence of this sort will be judged case by case by the instructor and, if it is deemed valid under the above description, a make-up exam will be given. 5

6 Grading Grading: Homework: 5% In-class quizzes (exact homework questions): 25% Hour Exam: 30% Final Exam: 35% Class Attendance: 5% Bonus: Identify errors and suggest corrections Suggest improvements Design problems 6

7 Topics Covered Gain an understanding of the power system, future trends, and needs. Establish an understanding of real and reactive power flow, power factor correction on a per phase basis with extension of concepts to three phase circuits (Chapters 2-3) Model transformers and transmission lines at an appropriate level to permit calculations under various load conditions (Chapters 4-5) Introduce students to the study of load flow and gain an understanding of iterative solution techniques leading to the use of computer simulation methods (Chapter 6) Understand the sequence component technique and perform it for system fault analysis. (Chapters 8-9) 7

8 Topics Covered 1 T1 2 L3 7 T5 8 G1 T2 3 G3 L1 L2 4 6 T3 T4 5 G2 8

9 Outline Notation (power, energy) Power system components Power system voltage structure Power system frequency Single phase and three-phase Evolution of the U.S. power industry 9

10 Notation - Power and Energy Power: Instantaneous consumption of energy Installed U.S. generation capacity is about 900 GW ( about 3 kw per person) Maximum load of Clarkson Campus about 2 MW Power Units Watts = voltage x current for dc (W) kw 1 x 10 3 Watt MW 1 x 10 6 Watt GW 1 x 10 9 Watt Energy: Integration of power over time, is what people want from power systems U.S. electric energy consumption is about 3600 billion kwh (about 13,333 kwh per person, which means on average we each use 1.5 kw of power continuously) Energy Units Joule = 1 Watt-second (J) kwh Kilowatthour (3.6 x 10 6 J) Btu J; 1 MBtu=0.292 MWh (British thermal unit) 10

11 Power System Overview 11

12 North American Electric Reliability Corporation Interconnections 12

13 Power System Components Generation Source of power, generators Transmission, subtransmission Transmits power, transmission network, transformers Distribution Load Distributes power, distribution network, transformers Consumes power 13

14 Generation Mix (U.S.) 14

15 Power System Voltage Structure Low voltage 120V, 208V, 140V, 480V, 600V Medium voltage 2.4kV, 4.16kV, 4.8kV, 6.9kV, 12.47kV, 13.2kV, 13.8kV, 23kV, 24.94kV, 34.5kV, 46kV, 69kV High voltage 115kV, 138kV, 161kV, 230kV Extra high voltage (EHV) 345kV, 500kV, 765kV 15

16 Consumers Industrial sites: manufacturing, construction, mining, agriculture, fishing and forestry establishments Commercial sites: non-manufacturing businesses (hotels, motels, restaurants, wholesale, retail, health, social, educational) Residential sites: private households, residential buildings 16

17 Goals of Power System Operation Supply load with electricity at specified voltage specified frequency with minimum cost Complications No ideal voltage sources exit Loads are constantly changing Transmission & distribution system has resistance, inductance, capacitance and flow limitations Power system is subject to disturbances, such as lightning strikes. Thus, simple systems without redundancy will not work if any component fails Engineering tradeoffs between reliability and cost 17

18 Questions DC vs. AC 50Hz vs. 60Hz Single-phase vs. three-phase 18

19 DC vs. AC DC AC High loads of direct current could rarely be transmitted for distances of greater than one mile without introducing excessive voltage drops. Direct current could not easily be changed to higher or lower voltages. High voltage AC could be transmitted over long distances with lower voltage drops (thus greater transmission efficiency), and then conveniently stepped down to low voltages for use in homes and factories. 19

20 50Hz vs. 60Hz 20

21 50Hz vs. 60Hz Each has advantages and disadvantages, and on balance it likely makes no real difference. 50Hz Smaller reactance: lower reactive voltage drops and higher transmission capacity. Less line reactive charging. 60Hz The equipment (generator, transformer) is generally smaller with the same rating. Higher eddy and hysterisis losses increase with frequency (skin effect) For cables capacitive leakage becomes an issue for higher frequency. 21

22 Single-Phase vs. Three-Phase Advantages of three-phase over single-phase Reduced capital and operating costs of transmission and distribution, as well as better voltage regulation The balanced three-phase system, while delivering the same power, requires only half the number of conductors needed for the three separate single-phase systems. The total I 2 R losses in the three-phase system are only half those of three separate single-phase systems. Line-voltage drop (IR) between the source and load in the threephase system is half that of each single-phase system. In a balanced three-phase system, instantaneous power delivered to the external load is constant rather than pulsating as it is in a single-phase system. 22

23 Evolution of the U.S. Power Industry Early 1880 s Edison introduces 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 1893 First 3-phase transmission line operating at 2.3 kv 1896 ac lines deliver electricity from hydro generation at Niagara Falls to Buffalo, 20 miles away 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 23

24 Evolution of the U.S. Power Industry 1935 Congress passes Public Utility Holding Company Act 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 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 Regulatory 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 24

25 Evolution of the U.S. Power Industry 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 25

26 Restructuring: What & Why What is Restructuring Unbundling electric utilities from vertically-integrated monopolies into separate generation, transmission and distribution entities. Let market forces drive the price of electric supply. Reduce the net cost through increased competition. Goal Reduce energy charges through a competitive market. More customer choice by creating an open access environment that will allow consumers to choose a provider for electric energy. Level of service reliability can be priced for customers. More business opportunities for selling new products and services. 26

27 Vertical Monopolies Within a particular geographic market, the electric utility had an exclusive franchise 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 Vertically Integrate d Utility Ge neration Tie-Lines Transmission Tie-Lines Distribution Customers 27

28 Vertical Monopolies It was a cost plus business Identifying allowed costs and investments Setting an allowed rate of return so that the utility will have the appropriate level of earnings on its investment Required revenues (per MWh) remain fixed for certain periods. This provides an incentive for the utility to reduce cost. The utility earns higher rates of return by incurring lower costs than the costs anticipated 28

29 Restructured Power Industry 29

30 Restructured Power Industry 30

31 Restructured Power Industry Power Flow vs. Money Flow GENCO Broker TRANSCO Marketer DISCO Retailer Aggregator Power Flow Customer Money Flow 31

32 Electricity Market National Overview 32

33 Average Electricity Retail Price 33

34 August 14 th, 2003 Blackout 34

35 Smart Grid The smart grid calls for the evolution to a 21 st century power grid that connects everyone to clean, abundant, affordable, and reliable electricity anytime, anywhere. The smart grid will integrate advanced techniques, including all kinds of generation sources, customer participation, storage devices, and distributed intelligent controllers, into electric grid. Accommodates all generation and storage options Enables active participation by consumers Enables new products, services, and markets Operates resiliently against physical and cyber attacks, and natural disasters [DOE08a] U.S. Department of Energy, The smart grid: an introduction, Available online at /DocumentsandMedia/ DOE_SG_Book_Single_Pages(1).pdf,

36 Smart Grid - Consumer Opportunities Utility Com m unications Internet Consum er Portal & Building EMS Efficient Building System s Renew ables PV Dynamic System s Control Distribution Operations Advanced Metering Control Interface Plug-In Hybrids Data Management Distributed Generation & Storage Smart End-Use Devices Energy efficiency and demand response is a driver that will greatly accelerate the creation of a smart grid 36

37 Customer Involvement 37

38 Concept of Microgrid Microgrids are small-scale, LV networks designed to supply electrical and heat loads for a small community. Microsources are equipped with power electronic interfaces (PEIs) and controls to provide the required flexibility as a single aggregated system with specified power quality and output. Differences between microgrids and conventional power plants: Microsources are of much smaller capacity. Microsources at distribution voltage can be directly fed to the utility distribution network. Microsources are normally installed close to customer premises so that electrical/heat loads can be efficiently supplied with satisfactory voltage and frequency profiles and negligible line losses. 38

39 Microgrid Integration Microgrid objectives are to improved reliability, self-healing, distributed control. Microgrid is modular with small capacity that is geographically dispersed and located near the load points. Physical proximity can also reduce the transmission and distribution losses. Microgrid utilizes non-conventional/renewable energy resources which will reduce fossil fuel usage. Microgrid reduces environmental pollution and global warming. Microgrid includes cogeneration plants that utilize wasted heat to increase the overall energy efficiency. Microgrid can be interconnected in semi-autonomous power systems or connected to utility distribution network. 39

40 Concept of Microgrid Generaion Transmission HV Switchyard Sub-Transmission Distribution Switchyard Microgrid 40

41 Microgrid Structures Home Microgrid 41

42 Microgrid Structures Community Microgrid Structure 42

43 Microgrid Structures Corporate Building Microgrid 43