net metering and utility interconnection
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Net Metering and Utility Interconnection. Presented by : Bill Brooks Brooks Engineering. Technical Interconnection Issues: Codes and Standards. Who Has a stake in the PV Industry?. Million Solar Roofs Partnerships Electric utility companies - PowerPoint PPT PresentationTRANSCRIPT
Net Metering and Utility Interconnection
Presented by:
Bill BrooksBrooks Engineering
Technical Interconnection Issues: Codes and Standards
Who Has a stake in the PV Industry?
Million Solar Roofs Partnerships Electric utility companies Electric customers wanting to install
a PV system PV component manufacturers PV equipment and system dealers Local jurisdictions enforcing building
codes
Why Do We Need PV Codes and Standards?
To facilitate the broad acceptance of the technology among local jurisdictions and interconnecting utilities.
To maintain minimum requirements for PV products and their installation.
To standardize and reduce the cost of testing and certification.
Who sets codes and standards?
National Fire Protection Association (NFPA)• National Electrical Code (NEC)
- Electrical Power System Installation--developed in conjunction with electrical trade and industry experts.
Underwriters Laboratory (UL)• Standards for Electrical Equipment Safety--developed in
conjunction with manufacturers. Institute of Electrical and Electronic Engineers
(IEEE)• Standards for electrical and electronic equipment--
developed in conjunction with applicable industry experts.
International (IEC, CENELEC, etc…)
What are the applicable codes and standards for PV systems?
NEC Article 690 - Solar Photovoltaic Systems - Building codes - UBC, SBC, BOCA, local codes
UL Standard 1703, Flat-plate Photovoltaic Modules and Panels
IEEE 929-2000, Recommended Practice for Utility Interface of Photovoltaic (PV) Systems (approved in January 2000)
UL Standard 1741, Standard for Static Inverters and Charge Controllers for Use in Photovoltaic Power Systems (published in May 1999)
What are the common interests of Utilities and PV manufacturers?
Provides predictable requirements for design and installation.• Utility protection departments need to reduce
costs.• Inverter manufacturers need to standardize their
designs to keep costs lower. Over 3000 utilities with a similar number of
interconnection requirements.• Consensus IEEE standard makes it unnecessary
for utilities to utilize an independent standard.• Inverter manufacturers can build one design that
is widely applicable.
Utility Interconnection Issues
Personnel safety Equipment protection Service reliability Power quality
Utility Interconnection Requirements
IEEE standard 929 UL standard 1741 Utility practice and requirements Public utility commission statutes
UL 1741 Standard for Static Inverters and Charge Controllers for Use in Photovoltaic Power Systems
First released in May of 1999
Has been revised to match IEEE 929-2000
Compliance with revised document required on November 7, 2000)
New title reads “Standard for inverters, converters, and controllers for use in Independent Power Systems.”(Nov 8)
Underwriters Laboratories Inc.®
Subjects 1741 333 Pfingsten RoadNorthbrook, IL 60062March 3, 1999
TO: Industry Advisory Group of Underwriters Laboratories Inc. for Power Conditioning Units for Use in Residential Photovoltaic Power Systems,Electrical Council of Underwriters Laboratories Inc.,Subscribers to UL's Listing Services for Photovoltaic Charge Controllers (QIBP),Subscribers to UL's Listing Services for Photovoltaic Power Systems Accessories (QIIO),Subscribers to UL's Listing Services for Power Conditioning Units for Use in Residential Photovoltaic Power Systems (QIKH), andSubscribers to UL's Listing Services for AC Modules (QHYZ)
SUBJECT: Request for Comments on the Proposed First Edition of the Standard for StaticInverters and Charge Controllers, UL 1741; PROPOSED EFFECTIVE DATE
Attached as Appendix A for your review and comment are proposed requirements for UL 1741.Questions regarding interpretation of requirements should be directed to the responsible UL Staff.Please see Appendix B of this bulletin regarding designated responsibility for the subject productcategories.
Please note that proposed requirements are of a tentative and early nature and are for reviewand comment only. Current requirements are to be used to judge a product until theserequirements are published in final form.PROPOSED EFFECTIVE DATE
The proposed requirements will necessitate a review and possible retest of currently Listedproducts. Therefore, UL proposes that the new requirements become effective 18 months afterpublication. This is intended to provide manufacturers with sufficient time to submit modifiedproducts for investigation and to implement the necessary changes in production. Please notethat this also includes the time that will be needed by UL to conduct a review of the modifiedproduct.
RATIONALE
The first edition of the Standard for Static Inverters and Charge Controllers for Use inPhotovoltaic Power Systems, UL 1741, was proposed in the subject bulletin dated August 1,1997. The proposed Standard has been significantly revised since then. The revisions are aresult of the comments UL received from industry members regarding the proposed draft. Inaddition, the revisions were made to align the proposed Standard with the Ninth Draft ofRecommended Practice for Utility Interface of Photovoltaic (PV) Systems, P929, and other ULStandards. This bulletin proposes the revised first edition of the Standard for Static Inverters andCharge Controllers for Use in Photovoltaic Power Systems, UL 1741.
UL®
What is UL 1741 and how does it relate to IEEE 929?
First official version published in May of 1999. “Final” version released November of 2000.
1741 incorporates the testing required by IEEE 929 (frequency and voltage limits, power quality, non-islanding inverter testing)
1741 testing includes design (type) testing and production testing. Line-tie inverters should have the words
“Utility-Interactive” printed directly on the listing label—this makes identification of the listing much more straightforward (several inverter manufacturers currently using this designation).
How Does a Utility, or a PV-System Purchaser, Know If An Inverter Meets The Requirements of IEEE 929?
If it meets the testing requirements of test standard UL 1741
and has the words “Utility-Interactive” printed directly on the listing label
Terms and Conditions for Interconnection
May involve the following:• Metering options• Size restrictions on metering options• Carryover credit on monthly billings• Net Meter or differing buy and sell rates• Outdoor disconnect requirements• Insurance requirements• Interconnection costs
Net Metered Systems in California(Similar to some other states)
Requires a contract with the serving utility company.
Inverter must be acceptable to utility for interconnection.
Utility also may have a list of acceptable manual disconnects to choose from.
Starting January 1, 1999, systems are to be billed on annual basis.
Starting January 1, 2001, systems may elect time-of-use net metering (up to 30% increased financial benefit)
P929Recommended Practice forUtility Interface ofPhotovoltaic (PV) Systems
Prepared by the Utility Working Group ofStandards Coordinating Committee 21, on Photovoltaics
Copyright © 1998 by the Institute of Electrical and Electronic Engineers, Inc.345 East 47th StreetNew York, NY 10017, USAAll Rights Reserved
This is an IEEE Standards Project, subject to change. Permission is hereby granted forIEEE Standards committee participants to reproduce this document for purposes ofIEEE standardization activities, including balloting and coordination. If this documentis to be submitted to ISO or IEC, notification shall be given to the IEEE CopyrightsAdministrator. Permission is also granted for member bodies and technical committeesof ISO and IEC to reproduce this document for purposes of developing a nationalposition. Other entities seeking permission to reproduce portions of this document forthese or other uses must contact the IEEE Standards Department for the appropriatelicense. Use of information contained in the unapproved draft is at your own risk.
IEEE Standards DepartmentCopyrights and Permissions445 Hoes Lane, P.O. Box 1331Piscataway, NJ 08855-1331, USA
IEEE 929-2000
Passed by IEEE Standards Board in January, 2000.
Represents an excellent primer on PV inverter interconnection issues.
The Need for PV Interconnection Standards
Many utilities were using “Rotating Machinery” requirements for PV systems
Many of the Interconnection Requirements were established in early “PURPA” days• too many requirements
• telemetery and “Utility Grade” type relays
• special (and costly) engineering were needed for each specific utility requirements
Purpose of IEEE 929
“This recommended practice contains guidance regarding equipment and functions necessary to ensure compatible operation of photovoltaic systems which are connected in parallel with the electric utility. This includes factors relating to personnel safety, equipment protection, power quality and utility system operation.”
• Power Quality
• Safety and Protection
IEEE 929 Working Group Consisted of Utilities and Industry
John Stevens, ChairSandia National Labs
D. Lane GarrettSouthern Co. Services
Miles Russell, Secr.Ascension Technology
Mike BehnkeTrace Technology
Steve Hester,
UPVGJohn MoriartyRaytheon
Bill BrooksN. Carolina Sol. Center
John Hoffner, Planergy(ex Austin Electric)
Chet NapikoskiArizona Public Service
John BzuraNew England Electric
Barry HornbergerPECO Energy
Jean PosbicSolarex
Steve Chalmers (Ret.)Salt River Project
Bob JonesRochester G&E
Jodi SmytheUnderwriters Labs
Joe ChauFlorida Power & Light
Greg KernAscension Technology
Chase SunPacific Gas and Electric
Doug Dawson (Ret.)Southern Cal Edison
Leslie LibbyAustin Electric
Rick WestUPG
Dick DeBlasioChair – IEEE SCC 21
Don LowebergIPP
Chuck WhitakerEndecon
Tom DuffyCentral Hudson G&E
Tron MelzlOmnion
Robert WillsAdvanced Energy Sys.
Chris FreitasTrace Engineering
Tim ZgonenaUnderwriters Labs
What Does IEEE 929Really Impact?
PV Array
InverterM
UtilitySystem
IEEE 929 Outline
Introduction 1. Overview (scope & purpose) 2. References 3. Definitions (inverter, islanding, PCC,
quality factor, etc…) 4. Power quality 5. Safety and protection functions Annexes
Power Quality
Power quality problems in general are rising because of proliferation of non-linear loads on utility systems -- all customers suffer
PV should not add to that problem
Power Quality
• Power Quality• 1. Service Voltage• 2. Voltage Flicker• 3. Frequency• 4. Waveform Distortion
• IEEE 519
• 5. Power Factor
Safety and Protection Functions
1. Response to Abnormal Utility Conditionsa. Voltage Disturbancesb. Frequency Disturbances c. Islanding Protectiond. Reconnect After a Utility Disturbance
2. Direct Current Isolation 3. Grounding 4. Manual Disconnect
Response to Abnormal Utility Conditions
Voltage (at PCC) Maximum Trip Time* V< 60 (V<50%) 6 cycles 60V<106 (50%V<88%) 120 cycles
106V132 (88%V110%) Normal Operation 132<V<165 (110%<V<137%) 120 cycles
165V (137%V) 2 cycles
Frequency (at PCC) Maximum Trip Time* <59.3 Hz 6 cycles
59.3 - 60.5 Hz (normal) -- >60.5 Hz 6 cycles
*”Trip time” refers to the time between the abnormal condition being applied and the inverter ceasing to energize the utility line. The inverter will actually remain connected to the utility to allow sensing of utility electrical conditions for use by the “reconnect” feature.
Terminology
Power Conditioning Unit or Inverter• Line-Commutated Inverters• Self-Commutated Inverters• Inverter Shut Down• The PV Inverter as a UPS• Power Factor• Controls Integrated into the Inverter
Islanding
The PV Inverter as a UPS
Some inverters are designed to provide uninterruptible power to critical loads
The power to critical loads is maintained when the connection to the utility is severed
When the inverter ceases to energize the utility line (due to abnormal conditions, the inverter will continue to maintain the loads connected to a special distribution panel isolated from the utility, also no power flows to the utility
IEEE 929- Annexes
• Annex A (Normative) – Minimum Test Procedure for a Non-Islanding PV Inverter
• Annex B (Informative) - Bibliography
• Annex C - PV Inverters and the Utility Interface (Terminology)
• Annex D - Disconnect Switches & Utility Procedures
• Annex E - Islanding as it Applies to PV Systems
• Annex F - The PV Inverter Under Utility Fault Conditions
• Annex G - Dedicated Distribution Transformer
ManualDisconnect Switch
PV Array
InverterM
LocalLoads
UtilitySystem
Islanding Testing
Why do we need testing?
Utility engineers are required to do testing of system protection equipment
Testing has a profound impact on an engineer’s understanding of how things work.• Example: New York utilities require special tests.
º Tests designed to pit PV inverters against notorious NY waveforms
º Three utility engineers from NY visited Sandia to witness tests
º After first day into three-day test procedure, they said, “Let’s do something more interesting.”
Anti-Islanding Requirements
“Typical” island (no balance between load and island)• Trip time - 10 cycles (to avoid interference with reclosing)
“Balanced” island (real power load between 50% and 150% of PV output, Q 2.5)• Trip time - 2 seconds
“non-islanding” test procedure:
The load should have a real power match as close as reasonable (at least within 20%) to the PV system output
and a Q (quality factor) 2.5, where Q=R(C/L)½
the selected Q 2.5 equates to an uncorrected power factor of 0.37. As power factor increases, Q decreases. Thus, the test requirement that Q 2.5 equates to lines with uncorrected power factors from 0.37 to unity
RLC load that has been tuned to 60Hz
Sandia Anti-Islanding Method Basic Concepts
Frequency and voltage trip points are used Error signal from frequency and voltage is
calculated each ½ cycle Frequency and voltage are then “tweaked” in the
same direction as error signal If tweaking results in change, then accelerated
tweaking results to push frequency or voltage to trip points
Test Circuit Used at Sandia
Inv#1
Inv#2
secondarydisconnect
primarydisconnect
distributiontransformer
R C L Inv#3
LMutility
“Less Than Sandia” SchemeBalanced load and generation (25% of Capacity)
25% Load 25% Gen Q=2.5
57
58
59
60
61
62
63
0 1 10 100 1000
Trip Time (cycles)
Fre
qu
ency
(H
z)
94
99
104
109
114
119
124
Vo
ltage (V
)
Voltage
Frequency
“Less Than Sandia” Scheme(125% of Inverter Capacity)
125% Load 100% Gen, Q=2.5
57
58
59
60
61
62
63
0 1 10 100 1000
Trip Time (cycles)
Fre
qu
en
cy (
Hz)
80
85
90
95
100
105
110
115
120
Vo
ltag
e (
V)
Voltage
Frequency
“Less Than Sandia” Scheme Balanced load and generation (100% Capacity)
100% Load 100% Gen, Q=2.5
57
58
59
60
61
62
63
0 1 10 100 1000
Trip Time (cycles)
Fre
qu
en
cy
(H
z)
94
99
104
109
114
119
124
Vo
lta
ge (
V)
Voltage
Frequency
Sample Test-Using Sandia Anti-Islanding Method
Note that trip time meets “typical” criteria even though test is with “balanced” conditions
SFS + SVSLoad: L+C, Qres = 3.7
108
112
116
120
124
128
132
0 1 10 100
Trip Time (cycles)
Vo
lta
ge
(V
)
Sample Motor Load Tests—Using Sandia Anti-Islanding MethodRequired trip time - 2 seconds
SFS + SVSLoad: Motor + C
565758596061626364
0 1 10 100
Trip Time (cycles)
Fre
que
ncy (
Hz)
Motor Load TestsGeneration to load ratio impacts
SFS + SVSLoad: Motor + C
0
10
20
30
40
50
60
70
80
0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20
Generation / Load Ratio
Tri
p T
ime
(cy
cles
)
IEEE 1547
Standard for Interconnecting Distributed Resources with
Electric Power Systems
Approved at June 2003 IEEE Standards Board Meeting
1. Standards: documents with mandatory requirements (shall)
2. Recommended Practices: documents in which procedures and positions preferred by the IEEE are presented (should)
3. Guides: documents in which alternative approaches
to good practice are suggested but no clear-cut recommendations are made (may)
IEEE Standards are Voluntary.
IEEE Standards Classification
1547 Standard for Interconnecting Distributed Resources with Electric Power Systems
1547.1 Draft Standard for Conformance Test Procedures for Equipment Interconnecting Distributed Resources with Electric Power Systems
P1547.2Draft Application Guide for IEEE P1547 Draft Standard for Interconnecting Distributed Resources with Electric Power Systems
Guide for NetworksGuide for Impacts
Guide for Islanding & Anti-Islanding
DP Specifications and Performance
Guide For
Interconnection System
Certification
P1547.3Draft Guide for Monitoring, Information Exchange and Control of DR Interconnected with EPS
The above schematic identifies existing standards development projects and potential future activities under discussion by P1547 Work Group members.
1547 Body of Standards
1547: Interconnection Is The Focus
Distributed Resource
(DR) unit
Area Electric Power
System (EPS)
Interconnection
System
Local EPS 1
Area Electric Power System (EPS)
Local EPS 3
PCC
Point of DR Connection
DR unit
Local EPS 2
Point of DR Connection
Point of Common Coupling (PCC)
Note: There can be any number of Local EPSs.
PCC
DR unit Load Load
1547 Interconnection Terms
INTRODUCTION
1.0 OVERVIEW 1.1 Scope 1.2 Purpose 1.3
Limitations
2.0 REFERENCES
3.0 DEFINITIONS
IEEE 1547 Contents
IEEE 1547 Contents
1.1 ScopeThis standard establishes criteria and requirements for interconnection of distributed resources (DR) with electric power systems (EPS).
1.2 PurposeThis document provides a uniform standard for interconnection of distributed resources with electric power systems. It provides requirements relevant to the performance, operation, testing, safety considerations, and maintenance of the interconnection.The requirements shall be met at the point of common coupling (PCC), although the devices used to meet these requirements can be located elsewhere. This standard applies to interconnection based on the aggregate rating of all the DR units that are within the Local EPS. The functions of the interconnection system hardware and software that affect the Area EPS are required to meet this standard regardless of their location on the EPS.The stated specifications and requirements, both technical and testing, are universally needed for interconnection of DR, including synchronous machines, induction machines, or power inverters/converters, and will be sufficient for most installations.1
1 Additional technical requirements and/or tests may be necessary for some limited situations.
4.0 INTERCONNECTION TECHNICAL SPECIFICATIONS AND REQUIREMENTS
4.1 General Requirements 4.2 Response to Area EPS Abnormal Conditions4.3 Power Quality 4.4 Islanding
5.0 INTERCONNECTION TEST SPECIFICATIONS AND REQUIREMENTS
5.1 Design Test 5.2 Production Tests 5.3 Interconnection Installation Evaluation 5.4 Commissioning Tests
5.5 Periodic Interconnection Tests ANNEX A (INFORMATIVE) BIBLIOGRAPHY
IEEE 1547 Contents
IEEE 1547 Contents
4.1 General Requirements4.1.1 Voltage Regulation (Don’t!)4.1.2 Integration with Area EPS Grounding (Coordinate)4.1.3 Synchronization (<5% voltage fluctuation, no flicker)4.1.4 Distributed Resources on Distribution Secondary Grid and
Spot Networks4.1.4.1 Distribution Secondary Grid Networks4.1.4.2 Distribution Secondary Spot Networks
4.1.5 Inadvertent Energization of the Area EPS (Don’t!)4.1.6 Monitoring Provisions4.1.7 Isolation Device (Disconnect Switch)4.1.8 Interconnect Integrity
4.1.8.1 Protection from Electromagnetic Interference (C37.90.2)4.1.8.2 Surge Withstand Performance (C62.41 or C36.90.1)4.1.8.3 Paralleling Device (withstand 220% of rated voltage)
IEEE 1547 Contents
4.2 Response to Area EPS Abnormal Conditions4.2.1 Area EPS Faults (detect faults, cease to energize)4.2.2 Area EPS Reclosing Coordination (coordinate)4.2.3 Voltage (<60V,106V – 132V, >144V)4.2.4 Frequency (59.3 – 60.5 Hz)4.2.5 Loss of Synchronism (not required unless there is flicker)4.2.6 Reconnection To Area EPS (up to 5 min, C84.1 Range B)
4.3 Power Quality4.3.1 Limitation of DC Injection (>0.5% of rated output current)4.3.2 Limitation of Flicker Induced by the DR (Don’t)4.3.3 Harmonics (~IEEE 519)
4.4 Islanding4.4.1 Unintentional Islanding (Don’t)4.4.2 Intentional Islanding (Don’t know)
Acrobat Document
IEEE 1547 Contents
5.0 INTERCONNECTION TEST SPECIFICATIONS AND REQUIREMENTS
5.1 Design Test5.1.1 Response to Abnormal Voltage and Frequency5.1.2 Synchronization5.1.3 Interconnect Integrity Test5.1.3.1 Protection From Electromagnetic Interference
(EMI)5.1.3.2 Surge Withstand Performance5.1.3.3 Paralleling Device
5.1.4 Unintentional Islanding 5.1.5 Limitation of DC Injection5.1.6 Harmonics
5.2 Production Tests
IEEE 1547 Contents
5.3 Interconnection Installation Evaluation5.3.1 Grounding Integration with Area Electric Power System5.3.2 Isolation Device5.3.3 Monitoring Provisions5.3.4 Area EPS Faults5.3.5 Area EPS Reclosing Coordination.
5.4 Commissioning Tests5.4.1 Unintentional Islanding Functionality Test
5.4.1.1 Reverse-Power or Minimum Power Test5.4.1.2 Non-Islanding Functionality Test75.4.1.3 Other Unintentional Islanding Functionality Tests
5.4.2 Cease to Energize Functionality Test
5.5 Periodic Interconnection Tests
Title Scope & Purpose P1547 Draft Standard for Interconnecting Distributed Resources with Electric Power Systems.
• This Standard establishes criteria and requirements for interconnection of distributed resources (DR) with electric power systems (EPS). • This document provides a uniform standard for interconnection of distributed resources with electric power systems. It provides requirements relevant to the performance, operation, testing, safety considerations, and maintenance of the interconnection.
P1547.1 Draft Standard for Conformance Test Procedures for Equipment Interconnecting Distributed Resources with Electric Power Systems.
• This Standard specifies the type, production, and commissioning tests that shall be performed to demonstrate that interconnection functions and equipment of a distributed resource (DR) conform to IEEE Std 1547. • Interconnection equipment that connects distributed resources (DR) to an electric power system (EPS) must meet the requirements specified in IEEE Standard P1547. Standardized test procedures are necessary to establish and verify compliance with those requirements. These test procedures must provide both repeatable results, independent of test location, and flexibility to accommodate a variety of DR technologies.
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SCC21 Interconnection Projects
Title Scope and Purpose P1547.2 Draft Application Guide for IEEE Standard 1547 for Interconnecting Distributed Resources with Electric Power Systems
• This Guide provides technical background and application details to support the understanding of IEEE 1547 Standard for Interconnecting Distributed Resources with Electric Power Systems. • This document facilitates the use of IEEE 1547 by characterizing the various forms of distributed resource technologies and the associated interconnection issues. Additionally, the background and rationale of the technical requirements are discussed in terms of the operation of the distributed resource interconnection with the electric power system. Presented in the document are technical descriptions and schematics, applications guidance and interconnection examples to enhance the use of IEEE 1547.
P1547.3: Draft Guide for Monitoring, Information Exchange and Control of Distributed Resources Interconnected with Electric Power Systems
• This document provides guidelines for monitoring, information exchange, and control for distributed resources (DR) interconnected with electric power systems (EPS). • This document facilitates the interoperability of one or more distributed resources interconnected with electric power systems. It describes functionality, parameters and methodologies for monitoring, information exchange and control for the interconnected distributed resources with, or associated with, electric power systems. Distributed resources include systems in the areas of fuel cells, photovoltaics, wind turbines, microturbines, other distributed generators, and, distributed energy storage systems.
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SCC21 Interconnection Projects
• Dr. Richard DeBlasio email: [email protected] voice: (303) 275 - 4333• Mr. Tom S. Basso email: [email protected] voice: (303) 275 - 3753 • IEEE SCC21 -- IEEE Standards Coordinating Committee 21 on Fuel Cells, Photovoltaics, Dispersed Generation, & Energy Storage http://grouper.ieee.org/groups/scc21/• P1547 Draft Standard for Interconnecting Distributed Resources
with Electric Power Systems -- web site and archives http://grouper.ieee.org/groups/scc21/1547 http://grouper.ieee.org/groups/scc21/1547/archives/
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NREL1617 Cole Blvd. MS-1614Golden, CO 80401-3393http://www.nrel.gov
SCC 21 Contact Information