DER Applications and Testing

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DER Applications and Testing

• Ben Kroposki, PE
• Senior Electrical Engineer - National Renewable
  Energy Laboratory

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DER Technology Portfolio
Examples
Reciprocating Engines
Fuel Cells
Advanced Turbines
Photovoltaics
Thermally Activated Technologies
Microturbines
Wind
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DER Grid Interconnection
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Residential Applications
Fuel Cells or Photovoltaic Systems
The CRN Residential Fuel Cell Demonstration
Handbook serves as a comprehensive guide to
residential fuel cell technology and related
issues.
http//www.nrel.gov/docs/fy02osti/32455.pdf.
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Residential Applications
Grid Parallel
Power Flow Power flows from the DER to the
customers dwelling and to/from the grid, both of
which are connected in parallel. Often this
arrangement is net metered.
Interconnect The DER interconnects with the grid
through a fused disconnect, which is accessible
to distribution service personnel, and an
internal disconnect under control of the power
plant. In the event of a short-term grid upset,
the inverter typically interrupts or stops
commuting. In the event of a longer upset, the
inverter opens an internal disconnect and likely
goes to idle while monitoring the grid and
waiting to reconnect after a preset time delay
after the grid returns to normal.
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Residential Applications
Grid-Independent
Power FlowPower flows only from the DER to the
customers dwelling. Thus, the DER must meet all
dwelling loads. This requires application
preplanning and perhaps load monitoring before
installation. The DER will likely have a
substantial battery storage system charged by the
cell stack at night to supplement the cell stack
during peak daytime loads.
Interconnect The DER connects to the dwelling
through a fused disconnect and perhaps an
internal disconnect for certain fault-clearing
events.
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Residential Applications
Dual Mode (Combination Grid Parallel and Grid
Independent)
Power Flow Power flows from the DER to the
customers dwelling and to/from the grid in
normal operation. In the event of a grid upset,
the power plant interrupts. In the event of a
serious grid event, it disconnects itself and the
dwelling from the grid and runs independently.
After a suitable delay after the grid returns to
normal, the inverter interrupts, and
grid-parallel operation is restored.
Interconnect The DER interconnects with the
grid through a fused disconnect. An internal DER
disconnect is provided for certain grid-parallel
upsets and may be provided for certain dwelling
grid-independent fault-clearing events.
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Commercial Applications Transfer Switch
Area Electric Power System (Area EPS)
Point of Common Coupling (PCC)
PCC
PCC
Transfer Switch
Point of DR Connection
Distributed Resource (DR) Unit
Load
Load
Distributed Resource (DR) Unit
Local EPS 1
Local EPS 2
Local EPS 3
Note Dashed lines are EPS boundaries. There can
be any number of Local EPSs
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Commercial Applications Parallel Switch
Area Electric Power System (Area EPS)
Point of Common Coupling (PCC)
PCC
PCC
Parallel Switch
Point of DR Connection
Distributed Resource (DR) Unit
Load
Load
Distributed Resource (DR) Unit
Local EPS 1
Local EPS 2
Local EPS 3
Note Dashed lines are EPS boundaries. There can
be any number of Local EPSs
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Commercial Applications Facility Microgrid
Area Electric Power System (Area EPS)
Point of Common Coupling (PCC)
PCC
PCC
Point of DR Connection
Point of DR Connection
Distributed Resource (DR) Unit
Load
Load
Distributed Resource (DR) Unit
Local EPS 1
Local EPS 2
Local EPS 3
Note Dashed lines are EPS boundaries. There can
be any number of Local EPSs
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Utility Applications Area EPS Microgrid
Area Electric Power System (Area EPS)
Point of Common Coupling (PCC)
PCC
PCC
Point of DR Connection
Point of DR Connection
Distributed Resource (DR) Unit
Load
Load
Distributed Resource (DR) Unit
Local EPS 1
Local EPS 2
Local EPS 3
Note Dashed lines are EPS boundaries. There can
be any number of Local EPSs
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Utility Applications Substation DER
EPS Source
Area Electric Power System (Area EPS)
Local EPS 2
PCC
Local EPS 4
Point of DR Connection
Load
Distributed Resource (DR) Unit
Load
DR
Load(s)
Local EPS 3
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DER Power Quality Issues

• Sustained Interruptions DG can provide backup
  power if designed to do so. This may improve
  reliability if designed and operated properly.
• Voltage Regulation DG can provide voltage
  regulation if allowed. This can also be a
  limiting factor as to penetration on a feeder.
• Harmonics There are harmonic concerns with both
  rotating and inverter based DG.
• Voltage Sag DG may be able to help keep voltage
  up, but only if allowed to do so.

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DER Microgrids for improved reliability
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DER-Grid Interconnection Operational Issues

• Short circuit contribution
• Protection coordination
• Voltage regulation
• Unintentional islanding
• Grounding and overvoltages
• --------- ------------------ -------------------
  
• Interconnection issues are real and resolvable
• e.g., specific to equipment, design, location,
  application, etc.

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IEEE 1547 Series Standards
1547-2003 Standard for Interconnecting
Distributed Resources with Electric Power Systems
1547.1-2005 Conformance Test Procedures for
Equipment Interconnecting DR with EPS
Current Projects
Future Projects
P1547.2 Application Guide for IEEE 1547 Standard
for Interconnecting DR with EPS

DG Specifications and Performance
Interconnection System Certification Guide
P1547.3 Guide for Monitoring, Information
Exchange and Control of DR
Guide for Grid/DG Impacts Determination
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
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IEEE 1547Technical Requirements

• General Requirements
• Voltage Regulation
• Integration with Area EPS Grounding
• Synchronization
• Secondary and Spot Networks
• Response to Area EPS Abnormal Conditions
• Voltage Disturbances
• Frequency Disturbances
• Disconnection for Faults
• Power Quality
• Limitation of DC Injection
• Limitation of Voltage Flicker
• Induced by the DR
• Islanding

• Inadvertent Energizing of the Area EPS
• Monitoring
• Isolation Device
• Loss of Synchronism
• Feeder Reclosing Coordination
• Immunity Protection
• Harmonics
• Surge Capability

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IEEE 1547.1 Interconnection Tests have been
incorporated into UL 1741 for product
certification
DER Interconnection Equipment Certification
Approach

• IEEE 1547
• Interconnection System Requirements
• Voltage Regulation
• Grounding
• Disconnects
• Monitoring
• Islanding

• UL 1741
• Interconnection Equipment
• Construction
• Protection against risks of injury to persons
• Rating, Marking
• Specific DR Tests for various technologies

• IEEE 1547.1
• Interconnection System Testing
• O/U Voltage
• and Frequency
• Synchronization
• EMI
• Surge Withstand
• DC injection
• Harmonics
• Islanding
• Reconnection

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NREL DER Test Facility
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Testing Interconnection Equipment
GE Universal Interconnection Technology (UIT)
ASCO Soft-Load Transfer Switch

• Validation of IEEE P1547 Interconnection Standard
  Tests
• Over/Under Voltage and Frequency Response
• Unintentional islanding test

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Test Results System Configuration
Unit under Test
Onan 125kW Generator
200kW Grid Simulator
Programmable Load Banks
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Test Results IEEE 1547 Response Times
  Response to Abnormal Voltage
Response to Abnormal Frequency
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Test Results

• Testing Results from ASCO SLTS Overvoltage
  Magnitude Test

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Test Results

• Testing Results from ASCO SLTS Overvoltage Time
  Test

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Test Results

• Testing Results from NPS DER Switch
  Synchronization Test

Testing synchronization around a specific voltage
and frequency window Using secondary injection
testing X shows where equipment does not meet
spec This equipment was recalibrated to meet spec.
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IEEE 1547 - Islanding

• Unintentional Islanding - For an unintentional
  island in which the DR energizes a portion of the
  Area EPS through the PCC, the DR interconnection
  system shall detect the island and cease to
  energize the Area EPS within two seconds of the
  formation of an island.
• Intentional Islanding - This topic is under
  consideration for future revisions of this
  standard. (IEEE 1547.4 covers this topic)

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Test Results

• Testing Results from ASCO SLTS Unintentional
  Islanding
• IEEE 1547 requirement is to disconnect within 2
  seconds of island formation

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Test Results

• Testing Results from ASCO SLTS Unintentional
  Islanding

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IEEE 1547 - Islanding

• Limited DR capacity as share of customer load
  If the aggregate DR capacity is less than
  one-third of the minimum load of the Local EPS,
  it is generally agreed that, should an
  unintentional island be formed, the DR will be
  unable to continue to energize the load connected
  within the Local EPS and still maintain
  acceptable voltage and frequency. In this case,
  it is expected that that the DR itself will
  respond by various means to cease to energize the
  island. These may include excitation system
  behavior for synchronous generators, overload or
  over/underspeed sensing, or the over/undervoltage
  relays or over/Underfrequency relays which are
  required elsewhere in IEEE 1547.
• Non-Islanding Inverter Many inverters are
  designed specifically such that they are unable
  to supply a load without the presence of the
  electrical system. The inverter, in many cases,
  will lock to the Area EPS frequency. The
  inverter controls may also be equipped with one
  of several anti-islanding means, which usually
  continually attempt to force the inverter off the
  power system frequency, such that, if the power
  system is unavailable, the inverter voltage and
  frequency will quickly deviate from nominal
  ranges to cause under/over voltage or frequency
  trips.
• Reverse Power Protection If the DR is intended
  to supply power only to its own Local EPS, and
  not to provide power to the Area EPS across the
  PCC, reverse power relays may be installed at the
  PCC to operate isolating devices. These
  isolating devices may be the generator isolation
  device itself, or, if the DR wishes to continue
  to support the Local EPS as an intentional
  island, may be at the PCC.
• Passive Protection Passive protection may use
  voltage and frequency relays as a means of
  anti-island protection, as detailed above. This
  passive scheme measures electrical variables at
  the PCC and detects conditions that indicate an
  island has been formed. This protection scheme
  is based on the DRs inability to satisfy a
  sudden change in load without a corresponding
  change in its voltage and/or frequency. In this
  instance, the voltage or frequency relays will
  take the unit off line. Besides under/over
  voltage and frequency relays, several means
  derived from voltage and frequency changes are
  also commonly used for anti-islanding detection,
  for example, phase or vector jump, rate of change
  of frequency.

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IEEE 1547 - Islanding

• Synchronous Generator Excitation System Controls
  Synchronous generators may also be equipped
  with excitation system controls that maintain a
  constant power-factor or constant power, and rely
  on the under/overvoltage or under/overfrequency
  relays to operate if the load on the generator
  does not match the generator output.
• For example, power factor control can be used as
  an anti-islanding method. The DR is set to
  regulate at a fixed power factor. This power
  factor should be selected to be intentionally
  significantly different from the load that would
  be isolated with the DR. If an island condition
  develops, the DR will either supply too little or
  too much VAR support resulting in a high or low
  voltage condition. For example, if the load
  power factor is 0.9 and the DR is regulating to a
  power factor of 1.0, the DR will not provide
  sufficient VAR support should an island form.
  This will result in an undervoltage condition
  which in turn will cause the generator to trip
  due to low voltage (assuming standard
  undervoltage protection per IEEE 1547).
• Active Protection Active protection will take a
  more proactive approach, and attempt to detect an
  island directly. Anti-islanding controls in an
  inverter fall into this category. In some
  cases, passive protection can be fooled if the
  generator is able to carry the load of the island
  without a substantial change in voltage or
  frequency. Some inverter manufacturers have
  added an additional active anti-islanding
  capability .
• One class of active scheme is to use external
  devices, for example, to actively inject current
  signal with certain frequencies other than
  fundamental frequency, and then measure voltage
  at those frequencies. Islanding will be detected
  by examining the impedance changes. (e.g. ENS
  device commonly used in Germany)
• Active schemes measure electrical variables at
  the PCC, but the response of the variables is
  checked against a deliberate variation in some
  aspects of the DR output. Active anti-islanding
  is more robust than passive, but even it cannot
  guarantee that an island will not develop in some
  rare cases. Anti-Islanding relays are available
  which continually monitor for minute momentary
  changes in the vector relationships of the
  current of voltage to detect events on the Area
  EPS which would form an unintentional island.
• Direct Transfer Trip Direct Transfer Trip may
  also be used, and is a very active and positive
  approach to assure that the DR ceases to energize
  an unintentional island. Direct transfer trip
  involves communication equipment both on the Area
  EPS and at the DR. The specific events on the
  Area EPS will be used to send a secure reliable
  communications signal to the DR to cause the DR
  to open isolation devices as needed to satisfy
  this requirement. Implementation of direct
  transfer trip will be addressed comprehensively
  in IEEE P1547.3, a recommended practice that is
  in the early development stages.

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References

1. Basso, T.S. and DeBlasio, R. "IEEE P1547 Series
   of Standards for Interconnection Preprint for
   IEEE Power Engineering Society Transmission and
   Distribution 2003 Conference and Exhibition"
   NREL/CP-560-34003. Golden, CO NREL, May 2003.
2. Basso T.S. and DeBlasio, R. IEEE 1547 Series of
   Standards Interconnection Issues. NREL Report
   No. 34882. September 2003.
3. Kroposki, B., Basso, T. and DeBlasio, R.
   Interconnection Testing of Distributed
   Resources Preprint for 2004 PES General Meeting,
   June 2004, NREL/CP-560-35569. Golden, CO NREL.
4. Distributed Energy Resources Interconnection
   Systems Technology Review and Research
   NREL/SR-560-32459
5. Universal Interconnection Technology Workshop
   Proceedings NREL/BK-560-32865
6. CRN Residential Fuel Cell Demonstration Handbook,
   http//www.nrel.gov/docs/fy02osti/32455.pdf.
7. Ye, Z. Dame, M. Kroposki, B. (2005).
   Grid-Connected Inverter Anti-Islanding Test
   Results for General Electric Inverter-Based
   Interconnection Technology. 24 pp. NREL Report
   No. TP-560-37200. http//www.nrel.gov/docs/fy05ost
   i/37200.pdf

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References

1. Kroposki, B. Englebretson, S. Pink, C. Daley,
   J. Siciliano, R. Hinton, D. (2003). Validation
   of IEEE P1547.1 Interconnection Test Procedures
   ASCO 7000 Soft Load Transfer System. 52 pp. NREL
   Report No. TP-560-34870. http//www.nrel.gov/docs/
   fy04osti/34870.pdf
2. Distributed Generation Opportunities and
   Challenges for the TD System, Michael Doyle and
   Reigh Walling, 2003 IEEE/PES Transmission and
   Distribution Conference
3. Interconnection and Integration Studies for Wind
   Farms, Jeff Smith, 2003 IEEE/PES Transmission and
   Distribution Conference
4. Electrical Power Systems Quality- 2nd Edition,
   Roger Dugan, Mark McGranaghan, Surya Santoso,
   Wayne Beaty, 2002, Chapter 9
5. IEEE 1547-2003 Standard for Interconnecting
   Distributed Resources with Electric Power Systems
6. IEEE 1547.1-2005 Standard Conformance Test
   Procedures for Equipment Interconnecting
   Distributed Resources with Electric Power Systems
7. Lynch, J. John, V. Danial, S. M. Benedict, E.
   Vihinen, I. Kroposki, B. Pink, C. (2006).
   Flexible DER Utility Interface System Final
   Report, September 2004--May 2006. 222 pp. NREL
   Report No. TP-560-39876. http//www.nrel.gov/docs/
   fy06osti/39876.pdf