Power Electronics in a Smart-Grid
Distribution System
Prof. Douglas C Hopkins, Ph.D.
Dir. Electronic Power and Energy Research Laboratory
ProfDCHopkins@gmail.com
www.DCHopkins.Com
Prof. Mohammed Safiuddin, Ph.D.
Dir. Power Conversion and Controls Laboratory
State University of New York at Buffalo
332 Bonner Hall
Buffalo, New York 14260-1900
+01-716-645-3115
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COPYRIGHT PERMISSION
Some material contained in this document may be covered by
one or more copyright restrictions and are noted to the
authors’ best abilities.
Those who have attended an IEEE Seminar presented by Dr.
Douglas C. Hopkins are granted sole use as an extension of
the presented seminar.
Others are granted permission for sole use for their personal
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Outline
Introduction
The Power Distribution System Identifying Critical Issues
• Course Admin
• Credentials
• Course Objective
• Standards
• Operating limits
• Case Study
UB Degree and Courses
“Smart Grid” Topical Discussion
System Structure of Interest
Background - ‘Transmission
System’ and FACTS
Concept development
3-ph, Symmetry, Harmonics
Power Control
Power Flow
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• Transformers
• SSPC/SSCB
• Advanced Power Switches
Case Studies
Technical Review
•
•
•
•
Power Electronics Opportunities
• AC v. DC
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Course Objective
This seminar focuses on the environment power electronics needs
to develop within to provide the “smart” delivery of electric power
from the sub-transmission system to the end user’s meter.
Topics are introduced from an electronics processing / power
electronics v. power systems perspective.
Excerpt from university course taught to power utility engineers.
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Masters of Engineering curriculum for practicing
electric utility engineers
Offered at the University at Buffalo
Synchronous live broadcast on a trimester schedule
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UB MEng* Degree Courses
EAS 521 Y Principles of Engineering Management I C. Chang
Basic engineering management functions of planning, organizing, leading, and controlling, as
applied to project, team, knowledge, group/department and global settings, including
discussion of the strengths and weaknesses of engineers as managers, and the engineering
management challenges in the new economy. Emphasis is placed on the integration of
engineering technologies and management. Students are to understand/practice the basic
functions in engineering management, the roles and perspectives of engineering managers,
and selected skills required to become effective engineering managers in the new millennium.
Text: Notes
EE 582 Y Power Systems Engineering I. D. C. Hopkins
Review of fundamentals of three-phase power systems, power circuit analysis, characterization
and modeling of power system components, such as transformers and transmission lines, for
study of power flow and system operation with extension to advanced power system
components.
Text: Power Systems Analysis & Design; Glover & Sarma - Chapters 2-5 & 8
EE 587 Y Special Topics in Electrical Power Distribution M. Safiuddin
System planning and design, surge protection, system protection, system power factor, power
system pollution, and system interfaces.
Text: ANSI/IEEE Stnd. 141-1993 [The Red Book], IEEE Press
*Synchronous on-line distance learning, accredited for internationally delivery
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UB MEng* Degree Courses (con’d)
EE 583 Z Power Systems Engineering II J. Zirnheld
Investigate transmission line characteristics of aerial and underground lines including
development of their symmetrical component sequence impedances, Steady-state
performance of systems including methods of network solutions.
Text: Power System Analysis & Design; Glover & Sarma - Chapters 6-13 (except 8)
EE 641Y Power System Protection-Theory & Applications Ilya Grinberg
Power Systems Relay Protection. Principles of relay techniques (classical and solid state), current
and potential transformers and their application in relaying technique, over-current, differential,
impedance, frequency, overvoltage and undervoltage relays, relay protection of overhead and
underground power lines, generators, transformers, motors, and buses.
Text: Protective Relaying Theory and Applications, edited by W.A. Elmore, Marcel Dekker, 2nd
Rev & Ex Edition, Sept 2003.
EE 540Y Static Power Conversion for Power Systems D. C. Hopkins
Principles of operation of static compensators and basic configurations; series, shunt and shuntseries; flexible ac transmission systems (FACTS); line and self commutated controllers,
configurations and control aspects; applications to power distribution systems; performance
evaluation and practical applications of static compensators.
Text: Understanding FACTS- Concepts & Technology of Flexible AC Transm. Syst.; Hingorani
and Gugyi
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UB MEng* Degree Courses (con’d)
EE 598- Contemporary Issues in Electrical Power Industry- [Independent Study] M.
Safiuddin
Energy Management Issues - Supply/Demand/Conservation
Electrical Power System Quality and Reliability
Industry Restructuring - Pains & Gains- Who is really in charge?
Electrical Power Generation and Global Warming; Cost Effectiveness Issues
EE 606Y- Distributed Generation: M. Safiuddin
Historical perspective of electric power industry, fundamentals of distributed generation,
economics of distributed resources, Micro-turbines, fuel cells, solar and wind power systems.
Text: Renewable and Efficient Power Systems; Gilbert M. Masters; IEEE Press;
*Synchronous on-line distance learning, accredited for internationally delivery
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“SMART GRID” - Topical Discussion
TOPICAL DISCUSSION WAS OMMITTED FROM BOOKLET
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Advanced Energy 2010 conference
The Advanced Energy 2010 conference includes
programs each morning, general sessions
featuring one or more keynote speakers, and a
poster session. The educational program includes
multiple sessions involving topic experts and
thought leaders on the following program tracks:
2010
!Energy Policy, Energy Sector Finance
!Battery/Energy Storage/Load Management
!Intelligent Transmission, Distribution & Smart Grid
!Solar, BioFuels, Wind, Geothermal, Tidal, Hydrogen
Economy
!Low Carbon Society, Climate Change & Sustainable
Building
!Intelligent Transportation
!Energy Efficient Data Centers
!Energy Efficient Lighting!Advanced Lighting
Research
"JimSmith" <jim.smith@stonybrook.edu>,
http://www.aertc.org/conference09/index.html
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OUR CHALLENGE
- LEGACY DOMANANCE All Smart Grid initiatives will need to integrate with the
Legacy Systems.
Utilities have tremendous precedent that has been
maintained because of the“deep pockets” they offer
when good things might go wrong.
What is the primary “Legacy” hurdle?
STANDARDS
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Standards - A Critical Element
NIST Special Publication 1108
NIST Framework and Roadmap for
Smart Grid Interoperability
Standards, Release 1.0
Office of the National Coordinator for Smart
Grid Interoperability
January 2010
www.nist.gov/public_affairs/releases/
smartgrid_interoperability_final.pdf
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A breakdown of what to follow in the
NIST Standards Activities
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Why NIST Framework
Under the Energy Independence and Security Act of 2007 (EISA), NIST
is assigned the
“primary responsibility to coordinate development of a framework that
includes protocols and model standards for information management to
achieve interoperability of Smart Grid devices and systems…”
There is an urgent need to establish protocols and standards for the
Smart Grid.
Deployment of various Smart Grid elements, including smart sensors on
distribution lines, smart meters in homes, and widely dispersed sources
of renewable energy, is already underway and will be accelerated as a
result of DOE Smart Grid Investment Grants etc.
Without standards, there is the potential for technologies developed or
implemented with sizable public and private investments to become
obsolete prematurely or to be implemented without measures
necessary to ensure security.
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Why NIST Framework (con’d)
Recognizing the urgency, NIST developed a
• three-phase plan to accelerate the identification of an initial set of
standards and
• to establish a robust framework for the sustaining development of the
many additional standards that will be needed and
• for setting up a conformity testing and certification infrastructure.
This document: NIST Framework and Roadmap for Smart Grid
Interoperability Standards, Release 1.0, is the output of the first phase
of the NIST plan.
• It describes a high-level conceptual reference model for the Smart Grid,
• identifies 75 existing standards that are applicable (or likely to be
applicable) to the ongoing development of the Smart Grid,
• specifies 15 high-priority gaps and harmonization issues (in addition to
cyber security) for which new or revised standards and requirements are
needed,
• documents action plans with aggressive timelines by which designated
standards-setting organizations (SSOs) will address these gaps,
• and describes the strategy to establish requirements and standards to help
ensure Smart Grid cyber security
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Lost in WHAT IS THE SMART GRID?
1.4 Content Overview - Areas worth reading
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Primary Players
The market place will
be a primary driver
and should not be
overlooked
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Smart Grid Information Networks
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1.4 Content Overview (Areas worth reading)
Excellent orientation to
the Smart Grid Thrust
Chapter 2, “Smart Grid Vision”
Chapter 3, “Conceptual Reference Model”
• presents a set of views (diagrams) and descriptions that are the basis for
discussing the characteristics, uses, behavior, interfaces, requirements, and
standards of the Smart Grid.
A “must follow”
Chapter 4, “Standards Identified for Implementation”
• presents and describes existing standards and emerging specifications
applicable to the Smart Grid. It includes descriptions of proposed selection
criteria, a general overview of the standards identified by stakeholders in the
NIST- coordinated process, and a discussion of their relevance to Smart Grid
interoperability requirements.
Chapter 5 describes sixteen "Priority Action Plans”
Chapter 6, “Cyber Security Risk Management Framework and Strategy”
Chapter 7, “Next Steps”
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What is important about the NIST REPORT and
what is important for us to follow?
1.3.2 Applications and Requirements
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1.3.2 Applications and Requirements
1.3.2 Applications and Requirements: Eight Priority Areas
To prioritize its work, NIST chose to focus on six key functionalities plus
cyber security and network communications,
• i.e. aspects that are especially critical to ongoing and near- term
deployments of Smart Grid technologies and services, including priority
applications were recommended by FERC in its policy statement:23
These “Areas” are: … [by color of importance to power electronics
opportunities]
Peripheral interest with traditional support from existing products
Direct interest as technology can advance in integrated functionality
Primary interest by advanced power electronic systems
[23] Federal Energy Regulatory Commission, Smart Grid Policy, 128 FERC ¶ 61,060 [Docket No. PL09-4-000] July 16, 2009.
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1.3.2 Apps & Req’d Priority Areas
Peripheral interest with traditional support from existing products
Wide-area situational awareness:
Demand response and consumer energy efficiency:
Cyber security:
Network communications:
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1.3.2 Apps & Req’d Priority Areas (con’d)
Direct interest as technology can advance in integrated functionality
Advanced metering infrastructure (AMI):
• Currently, utilities are focusing on developing AMI to implement residential
demand response and to serve as the chief mechanism for implementing
dynamic pricing.
• It consists of the communications hardware and software, and associated
system and data management software that creates a two-way network
between advanced meters and utility business systems, enabling
collection and distribution of information to customers and other parties,
such as the competitive retail supplier or the utility itself.
• AMI provides customers real-time (or near real-time) pricing of electricity,
and it can help utilities achieve necessary load reductions.
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1.3.2 Apps & Req’d Priority Areas (con’d)
Primary interest by advanced power electronic systems
Energy storage:
• Means of storing energy, directly or indirectly.
• The significant bulk energy storage technology available today is pumped
hydroelectric storage. New storage capabilities, especially for distributed
storage, would benefit the entire grid, from generation to end use.
Electric transportation:
• Refers, primarily, to enabling large-scale integration of plug-in electric
vehicles (PEVs).
• Electric transportation could significantly reduce U.S. dependence on
foreign oil, increase use of renewable sources of energy, and dramatically
reduce the nationﾕs carbon footprint.
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1.3.2 Apps & Req’d Priority Areas (con’d)
Distribution grid management:
• Focuses on maximizing performance of feeders, transformers, and other
components of networked distribution systems and integrating with
transmission systems and customer operations.
• As Smart Grid capabilities, such as AMI and demand response, are
developed, and as large numbers of distributed energy resources and
plug-in electric vehicles (PEVs) are deployed, the automation of
distribution systems becomes increasingly more important to the efficient
and reliable operation of the overall power system.
• The anticipated benefits of distribution grid management include increased
reliability, reductions in peak loads, and improved capabilities for
managing distributed sources of renewable energy.
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NIST Report provides a comprehensive
SUMMARY of RELEVANT STANDARDS
for us to follow
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Cited Standards of interest (See RED later)
4 DNP3 - This standard is used for substation and feeder device
automation as well as for communications between control centers and
substations.
8 IEEE C37.118 - Synchrophasor Protocol (synchrophasor):
This standard defines phasor measurement unit (PMU) performance
specifications and communications.
9 IEEE 1547 Suite - This family of standards defines physical and
electrical interconnections between utility and distributed generation
(DG) and storage. [http://grouper.ieee.org/groups/scc21/dr_shared/]
19 IEEE P2030 Draft Guide for Smart Grid Interoperability of Energy
Technology and Information Technology Operation with Electric Power
System (EPS) and End-Use Applications and Loads.
• Standards, guidelines to be developed by IEEE P2030 Smart Grid
Interoperability.
23 IEEE C37.2-2008 - IEEE Standard Electric Power System Device
Function Numbers - Protective circuit device modeling numbering
scheme for various switchgear.
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Cited Standards of interest
24 IEEE C37.111-199 - IEEE Standard Common Format for Transient
Data Exchange (COMTRADE) for Power Systems (COMTRADE) Applications using transient data from power system monitoring,
including power system relays, power quality monitoring field and
workstation equipment.
26 IEEE 1159.3 - Recommended Practice for the Transfer of Power
Quality Data - Applications using of power quality data.
27 IEEE 1379-2000 Substation Automation - Intelligent Electronic
Devices (IEDs) and remote terminal units (RTUs) in electric utility
substations.
38 SAE J1772 - Electrical Connector between PEV and EVSE - Electrical
connector between Plug-in Electric Vehicles (PEVs) and Electric
Vehicle Supply Equipment (EVSE)
40 SAE J2847/1-3 - Communications for PEV Interactions; J2847/1
Communication between Plug-in Vehicles and the Utility Grid; J2847/2
Communication between Plug-in Vehicles and the Supply Equipment
(EVSE); J2847/3 Communication between Plug-in Vehicles and the
Utility Grid for Reverse Power Flow.
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Other NIST Standards Topics
5.14 Energy Storage Interconnection Guidelines (PAP 07)
What Energy storage is required to accommodate the increasing
penetration of intermittent renewable energy resources and to improve
Electric Power System (EPS) performance. Consistent, uniformly
applied interconnection and information model standards, supported by
implementation guidelines, are required for energy storage devices
(ES), power electronics interconnection of distributed energy resources
(DER), hybrid generation-storage systems (ES- DER), and plug-in
electric vehicles (PEV) used as storage.
Why Due to the initial limited applications of the use of power electronics
for grid interconnection of ES and DER, there are few standards that
exist to capture how it could or should be utilized as a grid-integrated
operational asset on the legacy grid and Smart Grid. For example, no
standards address grid-specific aspects of aggregating large or small
mobile energy storage units, such as Plug-in Electric Vehicles
(PEVs)….
http://collaborate.nist.gov/twiki-sggrid/bin/view/SmartGrid/PAP07Storage.
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Other NIST Standards Topics (con’d)
5.15 Interoperability Standards to Support Plug-in Electric Vehicles (PAP
11) Interoperability standards that will define data standards to enable the
charging of plug-in electric vehicles (PEVs) will support the adoption of PEVs
and related benefits. Standards are anticipated to be available by the end of
2010.
• [Task 6: Coordinate standards activities for electrical interconnection and safety
standards for chargers and discharging, as well as a weights and standards
certification and seal for charging/discharging. - UL, SAE, IEEE, NEC,NEMA]
http://collaborate.nist.gov/twiki- sggrid/bin/view/SmartGrid/PAP11PEV
7.3 Other Issues to be Addressed This section describes other major
standards-related issues and barriers impacting standardization efforts and
progress toward a fully interoperable Smart Grid.
• 7.3.1 Electromagnetic Disturbances Standards for the Smart Grid should consider
electromagnetic disturbances, including severe solar (geomagnetic) storm risks and
Intentional Electromagnetic Interference (IEMI) threats such as High-Altitude
Electromagnetic Pulse (HEMP).
• 7.3.2 Electromagnetic Interference The burgeoning of communications
technologies, both wired and wireless, used by Smart Grid equipment can lead to
EMC interference, which represents another standards issue requiring study.
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END - NIST Review
Onto IEEE Standards
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Standards of Critical Importance
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SAE J2293, IEEE P2030 & IEEE 1547
IEEE P2030 Smart Grid Interoperability Standards Development Meeting
January 26-29, 2010, Hosted by Detroit Edison, Detroit, MI
Energy transfer
system for
electric vehicles
SAE J2293
Energy Transfer
System for Electric
Vehicles
Communication,
control and
information (V2G)
Electrical functional
interconnection
between electric
grid and electric
vehicle (two-way
power flow)
IEEE 1547
Interconnection
Standards
IEEE P2030
Smart Grid
Interoperability
Standards
IEEE P2030 Smart Grid Interoperability Standards Development Meeting,Jan 26-29, 2010,Detroit Edison, Detroit, MI
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1547- 2003 Standard for Interconnecting Distributed Resources
with Electric Power Systems
1547.1 - 2005 Conformance Test Procedures for
Equipment Interconnecting DR with EPS
1547.2 - 2008 Application Guide for IEEE 1547
Standard for Interconnection of DR with EPS
Identified
in Report
to NIST
1547.3 - 2007 Guide for Monitoring, Information
Exchange and Control of DR
Current 1547 Projects
P1547.4 Guide for Design, Operation, and Integration
of DR Island Systems with EPS
P1547.5 Guidelines for Interconnection of Electric
Power Sources Greater Than 10 MVA to the Power
Transmission Grid
P1547.6 Recommended Practice for Interconnecting
DR With EPS Distribution Secondary Networks
Microgrids
Urban distribution
networks
http://grouper.ieee.org/groups/scc21/index.html
IEEE 1547 Interconnection Standards
P1547.7 Draft Guide to Conducting Distribution
Impact Studies for Distributed Resource
Interconnection
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!"
Distributed Energy Resources Interconnection
Distributed
Energy
Technologies
Fuel Cell
Interconnection
Technologies
Electric Power
Systems
Functions
PV
Utility
System
• Power Conversion
• Power Conditioning
• Power Quality
Inverter
Microturbine
Microgrids
• Protection
Wind
• DER and Load
Control
Energy
Storage
PHEV;
V2G
Generator
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• Ancillary Services
Switchgear,
Relays, &
Controls
Loads
Local
Loads
Load Simulators
• Communications
• Metering
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IEEE Standard Development Meeting
IEEE P2030 Smart Grid Interoperability Standards Development Meeting
January 26-29, 2010, Hosted by Detroit Edison, Detroit, MI
v. Interconnection
P2030 Title: “Guide for Smart Grid Interoperability of Energy Technology and
Information Technology Operation with the Electric Power System (EPS) and
End-Use Applications and Loads”
Scope:
This guide provides a knowledge base addressing
• terminology, characteristics, functional performance and evaluation
criteria, and
• the application of engineering principles for smart grid interoperability of
the electric power system with end-use applications and loads.
The guide discusses alternate approaches to good practices for the
smart grid.
IEEE P2030 Smart Grid Interoperability Standards Development Meeting,Jan 26-29, 2010,Detroit Edison, Detroit, MI
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!#
3 TASK GROUPS for P2030
9. Power Systems Intraoperability
•
•
•
•
•
•
9.1 Energy Sources
9.2 Transmission
9.3 Substation
9.4 Distribution
9.5 Load Side
9.6 Cyber Security
10. Information Systems
Intraoperability
• 10.1 Introduction, Purpose, and
Scope
• 10.2 Power Engineering
• 10.3 Architecture
• 10.4 Modeling
• 10.5 Security
• 10.6 Communications
11. Communications Systems
Intraoperability
• 11.1 Purpose and Scope
• 11.2 Models of the Grid
• 11.3 Categorized
Communications Use Cases
• 11.4 Architectures
• 11.5 Monitoring and Control
Issues
• 11.6 Communication aspects of:
Generation, Transmission,
Distribution, Microgrids, Load
Management
IEEE P2030 Smart Grid Interoperability Standards Development Meeting,Jan 26-29, 2010,Detroit Edison, Detroit, MI
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P2030 Draft
Check the standards DRAFT on
the web.
https://mentor.ieee.org/2030/bp/StartPage
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1547&P2030 Considerations in NIST Rpts
Energy Storage Systems, e.g., IEEE 1547/2030 extensions for storage
system specific requirements
Distribution Grid Management Initiatives, e.g., extensions of 1547 series
and/or P2030 series, including communications
Voltage Regulation, Grid Support, etc., e.g., develop specifications in
P1547 and/or P2030-series
Management of DER, e.g. Planned island systems
Static and Mobile Electric Storage, including both small and large electric
storage facilities.
Electric Transportation and Electric Vehicles.
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P1809 Electric Transportation
New Standard committee
First meeting - 18 February 2010
PRESENTATIONS Continuation:
DOE – Keith Hardy, Grid Interaction Tech Team Lead – 15 minutes
NREL – Tony Markel, Senior Engineer – 15 minutes
NIST – Eric Simmon, PAP11 Lead – 15 minute
SAE – Gery Kissel, Chair SAE J1772 – 10 minutes
SAE – Rich Scholer, Chair SAE J2847/J2836 -10 minutes
SAE – Robert Gaylen, Chair SAE Battery Committee – 10 minutes
APTA – Martin Schroeder, Chief Engineer – 15 minutes
EEI – Steven Rosenstock, Manager, Energy Solutions - 15 minutes
NRECA – Andrew Cotter, Senior CRN Program Management Advisor - 10
minutes
• IEEE SA – Mike Kipness, Program Manager, Technical Program Development –
10 minutea
•
•
•
•
•
•
•
•
•
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!$
END - Standards (YEA!)
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What is the Smart Grid?
How do we survive within the Legacy System?
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What is the Smart Grid?
[EPRI 2006]: “The term ‘Smart Grid’ refers to a modernization of the
electricity delivery system so it
monitors, protects and automatically optimizes the operation of its
interconnected elements—
from the central and distributed generator through the high-voltage
network and
distribution system, to industrial users and building automation systems,
to energy storage installations and to end-use consumers…”
Our discussion is from Sub-Transmission to the Meter
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Structure of Interest in a Nutshell
(1) & (2): Generation step-up to Transmission !115kV
(2): Flow is regulated by ISOs (Independent System Operators)
(2): General contrast between NE v. W -- Mesh v. Point-to-Point
(3) Distribution is "12kV
(12.47kV or 7,200V L-N)
(3) thru (4)
ARE MAIN FOCUS
(4) Local distribution is "4.8kV
down to 120V (4,160V or
2400 L-N)
TRANSFORMERS AND PROTECTION ARE OF MAIN INTEREST
Distribution transformer is on the pole;
Substation transformer is on the ground in the Distribution Substation/Switch Yard
Picture from: http://www.peco.com/pecores/customer_service/the_electric_system.htm
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Structure of Interest in a Nutshell (con’d)
“Traditionally,” system stability is
part of transmission
Transmission
!115kV
Sub-Transmission
Substation
5 to 20 MVA
(or higher)
See “Red Book”
12kV
Alternative
Energy
Sources
Industrial
Loads
Major resource for information is
the IEEE “Red Book”
“Local distribution” is considered
240V/480V
Focus on "12kV system, know
nuances of requirements and how
PElect can include protection.
Distribution
Substation
e.g. 4800k
(in NY)
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Breaker protects
transformer
Breaker protects
cabling
Some disconnects
can open under load
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Areas of interest
Voltage Ranges (ANSI C84.1 Standard)
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A Test Bed for Smart Power
Development
The Intelligent Substation
Proposed test bed at the University at Buffalo
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Power Electronic Applications
Distributed generation (DG)
• Renewable resources (wind and photovoltaic)
• Fuel cells and micro-turbines
• Storage: batteries, super-conducting magnetic energy storage, flywheels
Power electronics loads: Adjustable speed drives
Power quality solutions
• Dual feeders
• Uninterruptible power supplies
• Dynamic voltage restorers
Transmission and Distribution (T&D)
• High voltage dc (HVDC) and medium voltage dc
• Flexible AC Transmission Systems (FACTS): Shunt and Series
compensation, and the unified power flow controller
From: N.Mohan, “First Course on Power Electronics, 2005
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Site Development Smart Distribution Syst
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Development Platform-The Intelligent Substation
•Campus-integrated
•34.5kV dual feeds
•Multiple dist voltages
•Multiple renewables
• (50kW levels)
•AC & DC dist
•Circular pwr flow
•Advanced controls
• (Neural network ctrl)
•Environ. testing
Technology Areas:
1.
2.
3.
4.
5.
6.
7.
APEC’10, Palm Springs, CA
Distributed Generation – Green Power Conversion
Automation & Control – Artificial Neural Networks
Intelligent Sensors & Networks – Wired & Wireless
System Protection – AC/DC and FACTS systems
Energy Storage – Electrochemical, Electromechanical
Residential EMS [Energy Management Systems]
Interoperability between the Old & the New
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Utility Applications
Distributed Generation (DG) Applications
Wound rotor
Induction Generator
Isolated
DC-DC
Converter
AC
Wind
Turbine
PWM
Converter
DC
DC
AC
Generator-side
Converter
Utility
1f
Max. Powerpoint Tracker
Grid-side
Converter
Photo-voltaics Interface
Wind Power Generation with
Doubly Fed Induction Motors
From: N.Mohan, “First Course on Power Electronics, 2005
APEC’10, Palm Springs, CA
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© 2010, D. C. Hopkins
Utility Applications (con’d)
Power Quality Solutions for
•
•
•
•
voltage distortion
unbalances
voltage sags and swells
power outages
Power Electronic
Interface
Load
Dynamic Voltage Restorers (DVR)
Feeder #1
Solid State
Switches
LOAD
Feeder #2
Rectifier
Inverter
Filter
Critical
Load
Energy
Storage
Dual Feeders
Uninterruptible Power
Supplies
From: N.Mohan, “First Course on Power Electronics, 2005
APEC’10, Palm Springs, CA
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Utility Applications (con’d)
Transmission and Distribution: DC Transmission
• most flexible solution for connection of two ac systems
AC1
AC2
HVDC
AC1
AC2
MVDC
From: N.Mohan, “First Course on Power Electronics, 2005
APEC’10, Palm Springs, CA
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Background - T&D Systems and FACTS
What control is needed in the power syst?
Stability
Power flow control
Directional routing
Quality control
Power conversion (MVDC)
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Power and Control Sensitivity
Starting with Transmission Model…
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Transmission Line Models
Parameters of distributed inductance, capacitance and resistance
precisely define the “overhead” transmission line. However, for short
lines a simpler model can be used.
Three models estimate the transmission line
Short Lines < 50 mi. – only a series impedance
Distribution Lines
50< Medium Lines < 250mi – uses singular lumped parameters
250mi.< Long Lines – uses distributed parameters
Short lines are typically represented by inductance only. Resistance can
be lumped with the load.
Depending on system cost, reliability and location “CABLING” is used.
[Cabling is not included in this seminar]
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General power flow - simple line
jXB
Eg / !
+ I-
If " # $Eg % $VB
VB / 0
Find : Power to control
S B = PB + jQB = VB • I * , (receiving end)
r
I = Eg "# $ VB "0
(
) ( jX B )
!r %
j(# $90 o )
j(0$90 o ) (
I = ' Eg e
$ VB e
* XB
&
)
r+ %
$ j(# $90 o )
$ j(0$90 o ) (
I = ' Eg e
$ VB e
* XB
&
)
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!
Computing power transfered (flow)
Remember : S B = PB + jQB = VB • I *
o '
$
+ j(0"# +90 o )
2 + j(0"0 +90 )
S B = &VB Eg e
" VB e
) XB
%
(
[
= jVB Eg { cos("# ) + j sin("# )} " jVB2
]
XB
cos("# ) = cos(+# ); j cos( # ) = sin( # ); j sin( "# ) = " j sin( +# ) = cos( # )
Therefore :
!
!
[
S B = VB Eg sin( " ) + jVB Eg cos( " ) # jVB2
P
]
XB
jQ
!
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Real and Quadrature Power
Power[W]
Real Power (P) :
#V E
&
B g
P =%
sin( " )(
%$ X B
('
![rad]
S B = PB + jQB
Quadrature Power (QB ) :
$
'
j&VB Eg cos( " ) # VB )
%
(!
jQB =
XB
$V E
VB2 '
B g
)
= j&
cos( " ) #
X B )(
&% X B
(
)
APEC’10, Palm Springs, CA
![rad]
Quad Power[VARs]
!
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!
How can you change power flow?
jXB
Eg / !
•
•
•
•
+ I-
VB / 0
Real Power (P) :
# VB Eg
&
P =%
sin( " )(
X
%$ B
('
Influence the magnitude of the voltage from the source.
Influence the line reactance.
!
Influence the magnitude of the load bus voltage.
Influence the angle, !2, of the load. (! = / Eg - / VB )
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Introduction to FACTS Controllers
Conceptual overview of controllers
and how they can be used.
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Helping in power management
Controllers help distribution and transmission owners to:
• Control of power flow as ordered, ensure optimum flow, redirect flow
during emergencies, increase utilization of lowest cost generation, etc.
• Increase dynamic line loading to thermal limits adjusted for seasonal
and environmental conditions, and according to loading history.
• Increase transient stability, limit short-circuit currents and overloads,
manage cascading blackouts, and dampen electromechanical and subsynchronous resonances.
• Provide secure tie line connections to neighboring utilities and regions
thereby decreasing overall generation reserve requirements on both
sides.
• Reduce reactive power flows and loop flows, allowing the lines to carry
more active power.
• Provide greater flexibility in siting new generation, upgrading lines, etc.
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General placement
Series controller
DC
w/ storage
Shunt controller
DC
Inter-tie controller
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dc link
Unified series-shunt controller
(w, w/o storage)
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Alphabet soup for the controllers - these are the
definitions from the IEEE working group
Part I - SHUNT CONTROLLERS
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STATCOM is one of the key FACTS
Controllers and based on voltagesource converters (VSCs) or currentsource converters. The VSCs are
more cost effective and preferred.
on
Shunt controller
- voltage source
<v>=0
The capacitor voltage is
automatically adjusted as required to
serve as a voltage source for the
converter.
Shunt controller
- current source
STATCOMs can be designed to also
act as an active filter to absorb
system harmonics.
APEC’10, Palm Springs, CA
lc
-D
ire
ct
io
na
(STATCOM)
Bi
Static synchronous generator
operated as a shunt-connected static
VAR compensator whose capacitive
or inductive output current is
controlled.
v.
Static Synchronous Compensator
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Static Synchronous Generator (SSG)
A self-commutated switching power
converter supplied from an
appropriate electric energy source
and operated to produce a set of
adjustable multiphase output
voltages, which may be coupled to
an ac power system for the purpose
of exchanging independently
controllable real and reactive power.
•SSG is a combination of STATCOM
and energy source
Shunt controller
- voltage source
interface converter
energy
storage
•Supplies or absorbs power
•May use
•battery (Battery Energy Storage System (SSG-BESS)),
•flywheel,
•superconducting magnet (Magnetic Energy Storage (SSG-SMES)),
•large dc storage capacitor, another rectifier/inverter, etc.
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© 2010, D. C. Hopkins
Static VAR Compensator (SVC)
A shunt-connected static var generator or absorber whose output is
adjusted to exchange capacitive or inductive current so as to maintain
or control specific parameters of the electrical power system
A.K.A.: thyristor-controlled or thyristor-switched reactor for absorbing
reactive power, and/or thyristor-switched capacitor for supplying the
reactive power, or combination
SVC is based on simple SCRs and considered by some as a lower cost
alternative to STATCOM, although this may not be the case if the
comparison is made based on the required performance and not just
the MVA size.
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SVC-Thyristor Controlled Reactor (TCR)
A shunt-connected, thyristorcontrolled inductor whose
effective reactance is varied in a
continuous manner by partialconduction control of the thyristor
•TCR is a subset of SVC in which
conduction time and hence,
current in a shunt reactor,
controlled by a thyristor-based ac
switch with firing angle control
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SVC-TCR, Thyristor
Controlled Reactor
© 2010, D. C. Hopkins
SVC-Thyristor Switched Reactor (TSR)
A shunt-connected, thyristorswitched inductor whose effective
reactance is stepwise varied by
full- or zero-conduction operation
of the thyristor.
•TSR is made up of several shunt
connected inductors switched in
and out by thyristors
•Controls achieve step changes
in the reactive power consumed
from the system.
•Use of thyristor switches without
firing angle control results in
lower cost and losses, but without
a continuous control.
APEC’10, Palm Springs, CA
SVC-TSR, Thyristor
Switched Reactor
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SVC-Thyristor Switched Cap (TSC)
A shunt-connected, thyristorswitched capacitor set whose
effective reactance is stepwise
varied by full- or zero-conduction
operation of the thyristor.
•Thyristors switch shunt
capacitors units in and out
(without firing angle control) to
achieve step changes in the
reactive power supplied to the
system.
SVC-TSC, Thyristor
Switched Capacitor
•Unlike shunt reactors, shunt
capacitors cannot be switched
continuously with variable firing
angle control.
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Static VAR Gen. or Absorber
A static electrical device, equipment, or system capable of drawing
controlled capacitive and/or inductive current from an electrical power
system, thereby generating or absorbing reactive power. Generally
considered to consist of shunt-connected, thyristor-controlled reactor(s)
and/or thyristor-switched capacitors.
Both the SVC and the STATCOM are static VAR generators equipped
with appropriate control loops to vary the VAR output so as to meet
specific compensation objectives.
Static VAR System (SVS)
A combination of different static and mechanically-switched VAR
compensators whose outputs are coordinated.
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Thyristor Ctrl’d Braking Resistor (TCBR)
A shunt-connected thyristorswitched resistor to aid
stabilization of a power system or
to minimize power acceleration of
a generating unit during a
disturbance.
•TCBR involves cycle-by-cycle
switching of a resistor with
thyristor-based firing angle
control
•Can be utilized to selectively
damp low-frequency oscillations.
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SVC-TCBR, Thyristor
Switched Braking Resistor
© 2010, D. C. Hopkins
Alphabet soup for the controllers - these are the
definition from the IEEE working group
Part II - Series Controllers
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© 2010, D. C. Hopkins
Static Sync. Series Compensator (SSSC)
A static synchronous generator operated without an external electric
energy source as a series compensator whose output voltage is in
quadrature with the line current for increasing or decreasing overall
reactive voltage drop across the line
The SSSC may include transiently rated energy storage or absorbing
devices to enhance the dynamic response by temporary addition of real
power to increase or decrease the overall real (resistive) voltage drop
across the line.
• SSSC is one the most important FACTS Controllers. It is like a
STATCOM, except that the output ac voltage is in series with the line.
• It can be based on a VSC or current-sourced converter.
• Battery-storage or superconducting magnetic storage can be added to
inject a voltage vector of variable angle in series with the line.
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Interline Power Flow Controller (IPFC)
New/possible definition: Combination
of two or more SSSCs coupled via a
common dc link to facilitate bidirectional flow of real power
between the SSSCs, and are
controlled to provide independent
reactive compensation in each line.
The IPFC structure may also include
a STATCOM, coupled to the IPFC's
common dc link, to provide shunt
reactive compensation and supply or
absorb the overall real power deficit
of the combined SSSCs.
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Alphabet code
C
C
(Controlled)
(Capacitor)
T
S
(Thyristor)
(Series)
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S
R
(Switched)
(Reactor)
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Thyristor Ctrl’d Series Capacitor (TCSC)
Capacitive reactance compensator
consisting of a series capacitor bank
shunted by a thyristor-controlled
reactor (TCR) to provide smoothly
variable series capacitive reactance.
MOST COMMON
The TCSC uses SCRs
When the TCR firing angle is 180º,
the reactor is non-conducting and the
series capacitor has normal
impedance. As the firing angle is
advanced from 180º, the capacitive
impedance increases
When the TCR firing angle is 90, the
reactor becomes fully conducting,
and the total impedance becomes
inductive
APEC’10, Palm Springs, CA
TCSC, Thyristor
Controlled Series
Capacitor
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Thyristor-Sw. Series Capacitor (TSSC)
Capacitive reactance
compensator consisting of a
series capacitor bank shunted by
a thyristor-switched reactor to
provide stepwise control of series
capacitive reactance.
Switches inductors at firing angle
90º or 180º without firing angle
control to reduce cost and losses
of the Controller
TCSC, Thyristor
Controlled Series
Capacitor
Could combine thyristor control,
and thyristor switching.
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Thyristor-Ctr’d Series Reactor (TCSR)
An inductive reactance
compensator consisting of a
series reactor shunted by a
thyristor controlled reactor to
provide a smoothly variable
series inductive reactance.
When the firing angle of the
thyristor controlled reactor is 180º
degrees, it stops conducting, and
the uncontrolled reactor acts as a
fault current limiter
As the angle decreases, the net
inductance decreases until firing
angle of 90º, when the net
inductance is the parallel
combination of the two reactors.
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Thyristor-Sw. Series Reactor (TSSR)
:An inductive reactance
compensator consisting of a
series reactor shunted by a
thyristor switched reactor to
provide stepwise control of series
inductive reactance.
This is a complement of TCSR,
but with thyristor switches fully on
or off (without firing angle control)
to achieve a combination of
stepped series inductances
APEC’10, Palm Springs, CA
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© 2010, D. C. Hopkins
Alphabet soup for the controllers - these are the
definition from the IEEE working group
Part III - Combined Shunt and Series
Controllers
APEC’10, Palm Springs, CA
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© 2010, D. C. Hopkins
Unified Power Flow Controller (UPFC)
A combination STATCOM and SSSC
coupled via a common dc link (for
bidirectional flow of real power
between the two) and are controlled
to provide concurrent real and
reactive series line compensation
without an external electric energy
source.
The UPFC is able to control the
transmission line voltage,
impedance, and angle or,
alternatively, real and reactive power
flow in the line.
The UPFC may also provide
independently controllable shunt
reactive compensation.
Additional dc storage, can provide
further effectiveness
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Thyrst-Ctrl’d Phase Shifting Tfrmr
A phase-shifting transformer
(TCPST)
adjusted by thyristor switches to
provide a rapidly variable phase
angle.
Phase shifting is obtained by
adding a perpendicular voltage
vector in series with a phase.
The vector is derived from the
other two phases via shunt
connected transformers.
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Interphase Power Controller (IPC)
A series-connected controller in
each phase of inductive and
capacitive branches subjected to
separately phase-shifted
voltages.
The active and reactive power
can be set independently by
adjusting the phase shifts and/or
the branch impedances, using
mechanical or electronic
switches.
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Thyristor-Ctl’d Voltage Limiter (TCVL)
A thyristor-switched metal-oxide
varistor (MOV) used to limit the
voltage across its terminals
during transient conditions.
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Thyristor-Ctrl’d Volt. Regulator (TCVR)
A thyristor-controlled transformer
which can provide variable inphase voltage with continuous
control.
Uses a transformer with thyristorcontrolled tap changing or
Thyristor-controlled ac-ac
converter for injection of variable
ac voltage of same phase in
series with the line
Such a relatively low cost
controller can effectively control
the flow of reactive power
between two ac systems.
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© 2010, D. C. Hopkins
Technical Review & Discussion Concept Development
Brief Discussion of:
•
•
•
•
Symmetrical Components
Harmonics
Power Control
Power Flow
[FURTHER SLIDES ON TOPIC OMMITTED]
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Symmetrical Components
- CONCEPT ONLYAn easy method to understand unbalanced
system operation is through
Symmetrical Components
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To Analyze Unsymmetrical Systems:
1. Use direct network calculations or circuit simulation, or
2. Use “Symmetrical Coordinates” as proposed by Charles L. Fortescue
[AIEE Transactions, V37 Part 2, 1918], now know as “Symmetrical
Components”
Characteristics:
• System must be linear for superposition of Components
• All waves in Symmetrical Components are single-frequency sinusoids
• Symmetrical Components can be combined with Fourier Analysis to
understand harmonic effects and wave distortion.
The key idea of Symmetrical Component analysis is to decompose the
system into three sequence networks. The networks are then coupled
only at the point of the unbalance (e.g., the fault)
The three sequence networks are known as the: Positive Sequence,
Negative Sequence and Zero Sequence
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Concept of Symmetrical Components
We already understand how to map a general vector into two orthogonal
vectors that are on real and imaginary axes.
Now consider a set of three general phasors each having a unique
magnitude and phase. These can be mapped onto a set of symmetrical
phasors, not all uniquely defined.
Voltage of Current
Phasor
Im
Phasors with
Symmetrical Components
120°
c
120°
a
120°
Negative
sequence
b
Zero
sequence
b
Re
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Positive
sequence
ProfDCHopkins@gmail.com
a
c
© 2010, D. C. Hopkins
Sequence Set Representation
Any arbitrary set of three phasors, say Ia, Ib, Ic, and each having a
unique magnitude and phase (but all with same frequency) can be
represented as a sum of the three sequence sets
I a = I a0 + I a+ + I a"
I b = I b0 + I b+ + I b"
I c = I c0 + I c+ + I c"
!
!
The symmetrical components are:
I a+ ,I b+ ,I c+ are positive sequence set
!
I a" ,I b" ,I c" are negative sequence set
I a0 ,I b0 ,I c0 are zero sequence set
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!
Background Understanding
- CONCEPT ONLYBrief Discussions:
Harmonics and Fourier Series, Harmonic Power and
THD, Per Unit System
Not in notes
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Harmonics (i.e. Fourier Series)
Fundamentally important for power quality, harmonic
control and high frequency design
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The Basics
Any physically realizable periodic function, f(t) = f(t+T), (for period T) can
be written as a sum of sinusoids:
"
()
f t = a0 +
# [a
n
( )
( )]
cos nwt + bn sin nwt
n=1
where the sum is taken over n=1 to infinity, ! = 2"/T,
However, there is an easier view for conceptualization….
!
Magnitudes for each sinusoid
Time varying sinusoids displaced by 90˚
Note: for “even symmetry” about the y axis, bn = 0 ;
for “odd symmetry” about the origin, an=0
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© 2010, D. C. Hopkins
The Basics
Any physically realizable periodic function, f(t) = f(t+T), (for period T) can
be written as a sum of sinusoids:
"
()
f t = a0 +
# [a
( )]
( )
cos nwt + bn sin nwt
n
n=1
where the sum is taken over n=1 to infinity, ! = 2"/T,
!
However, there is easier view for conceptualization
()
a0 : Average of
a0 =
!
!
1
T
()
f t = f t
" +T
# ()
f t dt
"
!
APEC’10, Palm Springs, CA
2
an =
T
" +T
2
bn =
T
" +T
# f ( t) cos(nwt) dt
"
# f ( t) sin(nwt )dt
"
" = 2# $ freq , freq = 1
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T
© 2010, D. C. Hopkins
!
!
Polar Form (best for conceptualization)
We can also write
c0 = a 0 , # 0 = 0
$
( ) % cn cos(n"t + # n )
f t =
n=0
Of most interest
cn =
#
n
a n2 + b n2
= " tan "1
bn
an
Each cosine term, cn cos(n!t + "n), is called a Fourier Component or a
! Harmonic of the function f(t) with “n” harmonics.
• cn is the “amplitude” component;
• "n is the component phase;
• c0 = a0 is the dc component, the average value of f(t), c0 = <f(t)>.
The term c1 cos(!t + "1) is the “fundamental” of f(t), while 1/T is the
fundamental frequency.
In power, we seek a single desired frequency
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Harmonics in Circuits
A non-sinusoidal source can be decomposed into Fourier Components
Each component can be individually applied to the same “LINEAR”
circuit, and through “superposition,” the effects of each component
individually evaluated.
Harmonic Superposition is a major concept for switching circuits
v1(t)
v(t)
XL(f)
XC(f)
v2(t)
v3(t)
http://www.ipes.ethz.ch/
v0
http://www.ipes.ethz.ch/ipes/pfc/e_fourier.html
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© 2010, D. C. Hopkins
What about Harmonic Power?
( ) $ vn cos(n"t + # n )
i( t ) = $ i cos ( m"t + # )
Assume a voltage
vt =
and a current
m
with the same base frequency !.
i(t)
+
m
v(t)
"
!
What is the “power” flow in the circuit?
!
p t = v t "i t =
( ) ( ) ( ) ["
pavg
!
]
im cos()
ENERGY
% [$ $ ]dt
"
0
) '
"
= +
+
2#
n=0 * m=0
((
APEC’10, Palm Springs, CA
!
2#
'
pavg
!
"
=
2#
!
]["
vn cos()
&
2#
0
"
,
vn im cos( n"t + $ n ) cos( m"t + % m )dt .
.
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© 2010, D. C. Hopkins
Average Power
"
2#
&
2#
"
0
vn im cos( n"t + $ n ) cos( m"t + % m )dt
CRITICAL
TAKE-AWAY!
$ "
'
&
)
=
1
4
4
2
4
4
3
&
)
( )0 , m % n
n=0 % m=0
2#
+
"
"
( )dt = * vn im cos( & n ' ( m ) , n = m % 0
2
2# 0
+
v
i
,
n
=
m
=
0
, nm
"
!
pavg
##
$
!
%
Pavg = v0 i0 +
!
!
&
n=1
vn in
2 2
%
cos( " n # $ n ) =
RMS RMS
In
n
&V
cos( " n # $ n )
n=0
IMPORTANT: ONLY “same-frequency” harmonics yield REAL power.
Cross-frequency harmonics contribute REACTIVE power along with
reactive components.
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Harmonic Distortion
DISTORATION - If you only need a single frequency
out, such as zero frequency, then what are the other
frequencies doing for you?
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Harmonics w/ Duty Cycle variation
DT
" 1, ...
f t =#
$0 , ...
()
!
1
a0 =
T
"
2
T
#
an =
T +t0
t0
T +t0
t0
f(t)
1
0
DT
f ( t )dt =
=D
T
t0
f ( t ) cos( n"t )dt = ...
OR cn =
!
t0+T
2 sin( n"D )
, n#0
"
n
Fourier series of “generic” f(t)
!
2
f t =D+
"
()
&
'
!
sin n"D
(
n
n=1
) cos n#t $ %
(
n)
" n = n#t0
Harmonics of a Rectangular Signal with Duty Cycle
(http://www.ipes.ethz.ch/ipes/signalHarmo/e_harmo.html)
!
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Distortion is Fundamental to Switching
There will always be unwanted terms. A switching converter does
not produce perfect waveforms (ac or dc).
How much of the signal is harmonic?
Total harmonic distortion (THD) measures the distortion content as
a fraction of the fundamental.
"
2
n
#c
THD =
n= 2
c12
To use the RMS value:
I RMS =
"
1 ! 2
cn $ THD =
2
#
2
2
I RMS
% I RMS
n= 1
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2
I RMS
n= 1
n= 1
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Per Unit System of Calculations
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Three-Phase Per Unit System
1. Pick 3-ph bases for system: use L-L voltage,VB,LL, and complex
power, SB,3ø [VA]. (Often nameplate transformer data.)
2. Reflect the voltage base through the transformers, i.e. different
voltage bases – VB, all L-L. (Power passes directly.)
3. Calculate the impedance base
ZB =
VB2, LL
S B3!
=
( 3 VB , LN ) 2
3S 1B!
=
VB2, LN
S 1B!
Note - same impedance base as single phase!
Procedure is similar to 1-ph except we use a 3-ph VA base, and use
Line-to-Line voltage base. Always assume a balanced system.
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Three Phase Per Unit, cont'd
4. Calculate the current base, IB
I3B!
S B3!
3 S 1B!
S 1B!
=
=
=
= I1B!
3 VB , LL
3 3 VB , LN VB , LN
Same current basis as with single phase.
Convert actual values to per unit
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All Rights Reserved
Electric Power Distribution
and Utilization Standards
Primary information comes from the IEEE Color Books
Distribution Topics are primarily
from the “Red Book”
ANSI/IEEE - Std. 141-1993
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The IEEE Color Books
IEEE Std 141-1993: Recommended Practices for Electric Power
Distribution for Industrial Plants [RED]
IEEE Std 142-1991: Recommended Practice for Grounding of Industrial
and Commercial Power Systems [GREEN]
IEEE Std 241-1990: Recommended Practice for Power Systems in
Commercial Buildings [GRAY]
IEEE Std 242-1986: Recommended Practice for Protection and
Coordination of Industrial and Commercial Power Systems [BUFF]
IEEE Std 399-1990: Recommended Practice for Industrial and
Commercial Power System Analysis [BROWN]
IEEE Std 446-1987: Recommended Practice for Emergency & Standby
Power Systems for Industrial & Commercial Applications [ORANGE]
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The IEEE Color Books
IEEE Std 493-1990: Recommended Practices for the Design of Reliable
Industrial & Commercial Power Systems [GOLD]
IEEE Std 602-1986 : Recommended Practices for Electric Systems in
Healthcare Facilities [WHITE]
IEEE Std 739-1984: Recommended Practices for Energy Conservation
and Cost Effective Planning in Industrial Facilities [BRONZE]
IEEE Std 1100-1992: Recommended Practices for Powering and
Grounding Sensitive Electronic Equipment [EMERALD]
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NATIONAL STANDARDS
USA
ANSI-
American National Standards Institute.
NIST-
National Institute of Standards & Technology
ASTM-
American Society for Testing & Materials.
EEI-
Edison Electric Institute [Trade Assn. of Private Utilities].
EPRI-
Electric Power Research Institute.
IEEE-
Institute of Electrical & Electronics Engineers.
Mil.-
Military – Department of Defense.
NEMA-
National Electrical Manufacturers Association.
NFPA-
National Fire Protection Association NEC
OSHA-
Occupational Safety & Health Administration
UL-
Underwriters Laboratories, Inc. [Safety Standards].
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INTERNATIONAL STANDARDS
CANADA
CSA-
Canadian Standards Association.
GERMANY
VDE-
Verbandef Deutscher Elektrotechniker.
INTERNATIONAL (Headquarters- Geneva, Switzerland).
IEC-
International Electrotechnical Commission
ISO-
International Standards Organization.
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Placement of Transformers & BreakersUnderstanding System-Level Deployment Problems
Solid State Transformers (SSTs) and Solid State Circuit
Breakers* (SSCBs) will need to co-exist with magnetic
transformers and electromechanical breakers
Legacy systems must be understood and included in
the early phase of system planning and part of the
equipment design process when developing new
apparatus.
*see next page
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SSCB v. SSPC
The “Solid State Circuit Breaker” (SSCB) is typically considered to have a
simple open and closing function when activated, and can open under
fault.
The “Solid State Power Controller” (SSPC) is typically considered to have
included current sensing, and fault current profiling including possible
current limiting. SSPCs are not typically associated with power
distribution because of the lower power levels of operation.
In this seminar the SSCB will include reference to SSPCs also.
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Placement in Simple Radial System
Transformer
• Has predicable source as do the circuit breakers
Breakers
• The right side breakers are typically thought to be molded case, self
contained breakers.
• The left side breaker is directly controlled as part of the protection scheme
Simple RADIAL System
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Placement in Simple Ring Bus System
Ring Bus System (v. Radial) - Found in denser load areas
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Placement in Selective System
Primary Selective Radial System
Secondary Selective Radial Syst.
Transformers
Transformers (no special issues)
• Fed from either feeder, but
with predictable load
Breakers (no special issues)
Breakers (no special issues)
Protecting
Xfrmr
Protecting
Cabling
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Placement in Selective System (con’d)
Primary Loop Radial System • Similar to Primary Selective Radial System
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Load Expansion Alternatives
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Load Expansion Alternatives (con’d)
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Standards - Voltage Ranges
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ANSI C84.1 standard
The American National Standard Institute (ANSI) has developed the
Standard C84.1 which is designed to establish nominal voltage ratings
and operating tolerances for 60-hertz electric power systems between
100V and 230kV. The purposes of the ANSI C84.1 standard are to :
Promote a better understanding of the voltages associated with power
systems and utilization equipment to achieve overall practical and
economical design and operation.
Establish uniform nomenclature in the field of voltages
Promote standardization of nominal system voltages and ranges of
voltage variations for operating systems
Promote standardization of equipment voltage ratings and tolerances
Promote coordination of relationships between system and equipment
voltage ratings and tolerances
Provide a guide for future development and design of equipment to
achieve the best possible conformance with the needs of the users
Provide a guide, with respect to choice of voltages, for new power system
undertakings and for changes in old ones.
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Standard Voltages - Low Voltages
Standard Nominal System Voltages
Associated nonstandard System
Voltages
120
110, 115, 125
120/240
110/220, 115/230, 125/250
208Y/120
216Y/125
240/120
240
230, 250
480Y/277
460Y/265
480
440
600
550, 575
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Standard Voltages - Medium Voltages
Standard Nominal System Voltages
2400
Associated nonstandard System Voltages
2200, 2300
4160Y/2400
4160
4000
4800
4600
6900
6600, 7200
8320Y/4800
11 000, 11 500
12 000Y/6930
12 470Y/7200
13 200Y/7620
13 200
13 800Y/7970
14 400
13 800
20 780Y/12 000
22 860Y/13 200
23 000
24 940Y/14 400
34 500Y/19 920
34 500
33 000
46 000
44 000
69 000
66 000
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Standard Voltages - High Voltages
Standard Nominal System Voltages
Associated nonstandard System
Voltages
115 000
110 000, 120 000
138 000
132 000
161 000
154 000
230 000
220 000
Standard Nominal System Voltages
Associated nonstandard System
Voltages
345 000
500 000
765 000
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Ranges A & B
Range A :
Service Voltage : Electric supply systems shall be so designed
and operated that most service voltages will be within the
limits specified for Range A. The occurrence of service
voltages outside of these limits should be infrequent.
Utilization Voltage : Electrical systems shall be designed and
operated within the voltage range defined as Range A; which
most utilization voltages being specified within this range.
Utilization equipment shall be designed and rated to give
fully satisfactory performance throughout range A.
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Range A & B
Range B :
Service and Utilization Voltage: Range B includes voltages
above and below Range A limits that necessarily result from
practical design and operating conditions on supply or user
systems, or both. Although such conditions are a part of
practical operations, they shall be limited in extent, frequency,
and duration. When they occur, corrective measures shall be
undertaken within a reasonable time to improve voltages to
meet Range A requirements.
Insofar as practicable, utilization equipment shall be designed to
give acceptable performance in the extremes of the range of
utilization voltages, although not necessarily as good
performance as in Range A.
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Range of Ranges
copyrighted by IEEE
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Flicker (IEEE Std 141-1993)
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System Protection SSTransformer and SSCB Requirements
The SST and SSCB will need to open under full fault
current and perform in legacy systems as traditional CB
operate. A set of metrics are given as guide to Smart
Breaker development
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Fundamental considerations
Reliability- Denotes certainty of correct operation together with assurance
against incorrect operation from all extraneous causes.
Speed – to obtain the minimum fault clearing time and damage to
equipment.
Selectivity – Complete selectivity being obtained when a minimum
amount of equipment is removed from service for isolation of a fault or
other abnormality.
Economics – Maximum protection at minimum cost.
IEEE Std 242-2001, Recommended Practice for Protection and Coordination of Industrial
and Commercial Power Systems (IEEE Buff Book)
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Analysis of System and Protection
Even with the best design possible, materials deteriorate and the
likelihood of faults increases with age.
Operating records show that the majority of electric circuit faults originate
as phase-to-ground faults.
In grounded systems, phase-to-ground faults produce currents of
sufficient magnitude for detection by ground-fault responsive
overcurrent relays.
If the system neutral is grounded through a proper impedance, the value
of the ground-fault current can be restricted to a level that would avoid
extensive damage at the point of the fault, yet adequate for groundfault relaying.
In ungrounded systems, phase-to-ground faults produce relatively
insignificant values of fault current. In small installations, with isolated
neutral, the ground-fault current for a single line-to-ground fault may be
well under one ampere. Overcurrent relays are not generally used to
detect and isolate this low current fault.
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Distortion of Phase V & I During Faults
copyrighted by IEEE
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Normal and 3-ph fault
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Several types of faults
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Some types of Circuit Breakers
Overcurrent relays;
Voltage relays;
Overcurrent relays with voltage
restraint or voltage control;
Distance relays;
Directional relays;
Phase-sequence or reversephase relays;
Differential relays;
Volts/Hz over-excitation relays;
Current balance relays;
Frequency relays;
Ground-fault relays;
Temperature-sensitive relays;
Synch-check and synchronizing
relays;
Pressure-sensitive relays;
Pilot-wire relays;
Replica-type temperature relays;
Auxiliary relays;
Direct-acting trip devices for lowvoltage power circuit breakers;
Power fuses
IEEE_Std_C37.2._2008
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Time-Current (typical time-1 OC Relay)
copyrighted by IEEE
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Typical Electro-Mechanical
Solid State is much
faster. However, the
system must be
compatible with faster
response times.
copyrighted by IEEE
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Typical t-I plot for SS Trip Device
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Impulse Voltage Withstand Requirements
New standards and system requirements may be
needed for power electronics equipment to
economically withstand transient over-voltages
Surge voltages occur from, e.g. lightning and the
reflections from the resultant traveling waves
Cabling becomes more of a challenge
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Surge Voltage Propagation
When wavelengths are short compared to the physical length of
circuitry, then it may be necessary to use “distributed-constant”
representation
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Surge voltage propagation (con’d)
Inductance L and capacitance C are expressed in
per unit length.
Stored energy in inductance is # LI 2
Stored energy in capacitance is # CE 2
Equating the two, we get
Z0 =
E
=
I
L
C
The wave propagation velocity is expressed as 1/$LC
It approximates speed of light [1000 ft/µs]
Typical values of Z0:
200-400# for overhead Lines
20-50 # for insulated cables
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Amplification Phenomena
A traveling surge-voltage, encountering in succession junctions with
higher surge impedance, may have its voltage magnitude elevated to a
value in excess of twice the magnitude of the initial voltage.
E
10"
Et
20"
1.33E
40"
1.78E
70"
2.27E
4.54E
Voltage at the point of refraction = (E)(2Z2)/(Z2 + Z1)
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Insulation Voltage Withstand
Insulation tests and ratings:
Standards have been developed that recognize the need for electrical
equipment to withstand a limited amount of temporary excess voltage
stresses above and beyond the normal operating voltages.
Standardized factory tests:
• 1 minute high potential [ hi-pot] test at power frequency
• 1.2/50 full-wave voltage impulse test
• For low voltage [<1000 V] equipment, additional wave shapes are
prescribed in IEEE std. C62.41.2-2002
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IEEE C62.41.2-2002
copyrighted by IEEE
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100kHz Ring Wave (V & I)
IEEE C62.41.2-2002
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Full-wave voltage impulse test wave
BIL: Basic Impulse Insulation Level
BIL
1.2!s
50!s
For tables: 6-1,2,3,& 4 in IEEE C62.41.2
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Combination Wave for Short Ckt I
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Transformer Insulation Overvoltage Tests
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copyrighted by IEEE
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copyrighted by IEEE
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copyrighted by IEEE
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Harmonics in Distribution System
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Harmonics in the system
For system analysis purpose, the non-linear devices (e.g. power
electronics) can be generally treated as current sources of harmonics
The amount of harmonic voltage distortions depends upon Z v. f
characteristics as seen by the harmonic currents.
Higher the short circuit capacity of the system, lower the source
impedance of the system and, hence, lower the voltage distortions due
to harmonic currents.
Capacitor banks used for voltage control or reactive compensation can
be considered in parallel with the system when calculating the
commutating reactance, which would increase di/dt of commutation.
• Capacitance of insulated cables has similar effect.
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Higher Frequencies Elicit Resonance
Normal flow of harmonic currents
Capacitor bank resulting in series resonance
Parallel Resonance conditions
H resonance =
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Short circuit MVA
=
capacitor bank size in MVA
XC
XL
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System response characteristics
It is important to be able to analyze a system’s frequency response
characteristics in order to avoid having system resonance problems.
Harmonic currents flow from the non-linear load towards the point of
lowest impedance, usually the utility source.
Effects of harmonics can be grouped into three general categories
1.
Effects on the power system – additional losses, radiated and
conducted noise, signature problems ( submarines)
2.
Effects on the loads- motors/generators, transformers, power cables,
capacitors, electronic instrumentations, switchgear & relaying, static
power converters
3.
Effects on communications [SCADA systems] – Telephone
Interference Factor [TIF] weighing –
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Cable Derating v. Harmonic
for six-pulse converter
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Voltage Distortion Limits (!69kV)
Industry Standards--IEEE Std. 519- 1992
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Current Distortion Limits (120V - 69kV)
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Case Studies
Case Studies Presented Interactively
1. One study included herein
2. Remaining study not included
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My-T Acres Farm Project, Batavia, NY by Dr. Mohammed Safiuddin
Objectives:
Compares two methods of transmitting power to isolated
load:
Method 1: Transmits the available single-phase power to a motor
drive inverter.
Method 2: Converts 3-Phase AC to DC and transmits it to the same
motor drive.
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Background
500,000V !!!
120V
Transmission of 3-phase to isolated loads is expensive.
UNICO
Drive
Instead, Single-phase transmission would be more economical
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1-Ph v. DC for VSD at point-of-load
1-Phase AC transmission
DC transmission
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Comparison
System Efficiency W/VA
60
0.6
50
0.5
40
0.4
Ratio (P-out/VA-in)
Efficiency (%)
System Efficiency W/W
30
20
0.3
0.2
AC LINK
AC LINK
DC LINK
10
DC LINK
0.1
0
0
1008
1107
1207
1308
1507
1607
1008
1207
1308
1507
1607
Speed (RPM)
Speed (RPM)
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System Performance - THD
System Current THD
70.00
60.00
50.00
THD (%)
40.00
30.00
20.00
AC LINK
DC LINK
10.00
0.00
1008
1107
1207
1308
1507
1607
Speed (RPM)
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Conclusions
Both DC and Single-phase AC transmission are more cost effective than
the 3-phase AC transmission for isolated loads ( Limited by the load
values).
DC power link offers several advantages over AC link:
•
•
•
•
•
More efficient
Allows lower components ratings
Lower harmonic distortions on the grid supply.
Better power factor
Can be used to supply large loads.
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End - Printed Booklet
Prof. Douglas C Hopkins, Ph.D.
Dir. Electronic Power and Energy Research Laboratory
ProfDCHopkins@gmail.com
www.DCHopkins.Com
Prof. Mohammed Safiuddin, Ph.D.
Research Professor
State University of New York at Buffalo
332 Bonner Hall
Buffalo, New York 14260-1900
+01-716-645-3115
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