Title: WECC Board of Directors Meeting
1Wind Generation Interconnection and Integration
Status and Challenges
- WECC Board of Directors Meeting
- November 30, 2005Tucson, Arizona
Robert M. ZavadilVice-President Principal
Consultant144-E Market Place BoulevardKnoxville,
Tennessee 37922Tel (865) 691-5540 ext.
149bobz_at_enernex.comwww.enernex.com
2Wind Plant Interconnection History
- Early (1980s into 1990s)
- Wind generation viewed as curiosity
- Special care taken to design and protect grid
interface - Preferred action for turbines during grid
disturbance was to disconnect - California thing
- Mid 1990s
- Development of large wind generation facilities
outside of California - Increasing plant sizes crossed threshold for
interconnection evaluations - Control area penetration still negligible, so
studies were many times more of a formality - 2000 to present
- Continued growth of wind generation led to
questions that could no longer be prudently
neglected - West Texas voltage and transmission capacity
questions - Growing awareness of wind plant sensitivity to
grid disturbances, and possible consequences
(with further growth) - Recognition of the unique characteristics of
wind, and the potential for increased operating
costs as penetration grows (integration
questions) - Continued favorable environment for further
development of wind generation
3Interconnection vs. Integration
- Convenient categories for all issues and
challenges related to wind generation - Interconnection
- Questions are primarily technical, centered on
transmission network - Thermal, voltage, transfer limits
- System stability and security
- Focus in on events, contingencies, abnormal
conditions - Integration
- Larger emphasis on economics
- Involves interaction of all generators with all
loads - Transmission capacity also plays a role
- Focus on normal operating conditions
4Relationship to System Reliability
- Reliability is the driver for power system
engineering and operations practice - The transmission network is a major factor in
power system reliability - Interconnection
- New network elements must not jeopardize the
operation of any other network equipment - The ability of the system to withstand a major
disruption must not be diminished by the
connection of a new element - Integration
- Wind generation will likely result in
re-deployments of other network elements - All practices and mechanisms for maintaining
system reliability must not be infringed
5Status Wind Generation Interconnection in
North America
- Activities underway simultaneously at many levels
- Achieving convergence is a necessity
- Most individual interconnection procedures must
comply with FERC 2003a - Will also adhere to NERC view, as yet not fully
determined - Technical capabilities are increasing
- Growing database of wind turbine models for
analysis platforms - Increasing industry experience with power system
studies involving wind generation facilities - Consensus on technical performance requirements
- Much progress has been made over past five years,
but next few years should be interesting
nonetheless
6The Present - Interconnection
- A number of efforts to sort out Interconnection
issues for wind generation are underway in the
North America - FERC Order 2003a
- AWEA best practices
- NERC wind generation task force
- WECC reliability standards for wind generation,
model development - Alberta Electric System Operator (AESO)
interconnection guidelines - Western Area Power Administration transmission
issues related to wind development in the Dakotas - New York ISO Impact of Wind Generation on
Reliability of NYSBPS - Growing awareness of wind generation within the
IEEE Power Engineering Society (IEEE PES) - Wind Generation TF
- Seminars and special sessions
- Interest from other technical committees
formative stages - UWIG
7Wind Generation Technology
- Wind turbine electrical technology
- Conventional induction machines
- Induction machines w/ static power converter
control - A few utilize more exotic technology (e.g.,
direct drive) - Important considerations for integration studies
- Steady-state characteristics P, Q, PF
- Dynamic response to grid disturbances
- Intermittency variation of P Q with time
- Output quality
- Wind plant Technology
- Behavior of aggregate plant can depend greatly on
this element - Advanced capabilities with advanced SCADA
- Distributed static VAr generation
- Ramp rate control
8Interconnection Challenges
- Remote facilities
- Typically interconnection to weak transmission
network - Transmission capacity questions
- Reactive power dispatch
- Dynamic character of wind generation
- Reactive power planning for network must be
coordinated with wind plants - Interconnection requirements are evolving
- Were typically very simple
- Evolving to voltage control, dynamic reactive
power management
9Windplant Modeling Challenges
- How to model large number of relatively small
generators? - Unfamiliar generator technologies (relative to
conventional synchronous machines and generating
plants) - Sometimes extensive medium voltage system plant
Q is very dependent on MV system (I2X) - Auxiliary equipment and systems
- Switched capacitors on collector system
- Switched capacitors at interconnect substation
- Plant-level systems
- GE DVAR
- Variable and uncertain fuel supply
10Emergence of Grid Codes
- Burst onto the scene about four years ago
- Driven in U.S. by two major technical issues
(primarily) - Turbine sensitivity to grid voltage disturbances
(low-voltage ride-through) - Reactive power management / voltage control
- Led to major challenges for industry
- Turbine design
- Plant design
- Recognition of the wind industry uniqueness
- Short project lead times
- Modeling complexity
11FERC Order 2003a, 661
- Wind generation recognized as requiring some
special considerations in Order 2003a - Input from collection of stakeholders organized
by AWEA - Concerns captured as Appendix G to order
- Appendix G
- Developed by AWEA-led stakeholder group
- Low-voltage ride-through (right)
- Basic reactive power requirements
- Need for SCADA
- Issued by FERC as Order 661
- NERC objects to parts of 661, files request for
rehearing - FERC directs AWEA and NERC to resolve
Wind plant LVRT specification from Appendix G of
FERC Order 2003a
12NERC/AWEA Resolution on LVRT
- All wind generating plants subject to FERC Order
No. 661 and not covered by the transition period
must meet the following requirements - Wind generating plants are required to remain
in-service during three phase faults with normal
clearing (which is a time period of approximately
4 9 cycles) and single line to ground faults
with delayed clearing, and subsequent post-fault
voltage recovery to pre-fault voltage unless
clearing the fault effectively disconnects the
generator form the system. - The clearing time requirement for a three-phase
fault will be specific to the wind generating
plant substation location, as determined by and
documented by the transmission provider. - The maximum clearing time the wind generating
plant shall be required to withstand for a
three-phase fault shall be 9 cycles - after which, if the fault remains the wind
generating plant may disconnect from the
transmission system. - The wind generating plant shall remain
interconnected during such a fault on the
transmission system for a voltage level as low a
zero volts, as measured at the high voltage side
of the wind GSU.
13New LVRT Requirement per FERC (cont)
- This requirement does not apply to faults that
would occur between the wind generator terminals
and the high side of the GSU. - Wind generating plants may trip after the fault
period if this action is intended as part of a
special protection scheme. - Wind generating plants may meet the LVRT
requirements of this standard by (utilizing) the
performance of the generators or by installing
additional equipment (e.g., Static VAr
Compensators, etc.) within the wind generating
plant or by a combination of generator
performance and additional equipment. - Existing individual generating units that are, or
have been, interconnected to the network at the
same location at the effected date of the
Appendix G LVRT Standard are exempt from meeting
the Appendix G LVRT Standard for the remaining
life of the existing generation equipment.
Existing individual generator units that are
replaced are required to meet the Appendix G LVRT
Standard.
14Wind Generation Technology Trends
- Wind Turbines
- Continuing movement to variable speed
- Emergence of full-converter topologies
- Enhanced grid compatibility (driven by grid
codes) - Continued emphasis on production, availability
(low wind speed) - Wind Plants
- Increasing emphasis on interconnection behavior
of entire plant, not just turbine - Higher performance driven by grid codes (e.g.
LVRT, voltage control requirements - Other
- Research and development on advanced features
(e.g. intertial and governor response)
15NERC Wind Generation Task Force
- In wake of Order 2003a, established task force to
assess power system planning and reliability
issues related to wind generation - Task Force convened January, 2005 with cross
section of stakeholder technical representatives - Transmission owners/operators
- Regional Transmission Organizations
- Generating companies
- Wind Industry (AWEA UWIG)
- Objectives
- Identify any and all issues related to wind
generation that have implications for power
system reliability - Determine if issue can be addressed through
standards - Develop SARs (standards authorization requests)
for areas where new standards may be necessary - TF assignment complicated by ongoing,
comprehensive revision of NERC standards - Task Force Period of Performance CY2005
16WECC Wind Turbine Modeling Initiative - Drivers
- Wind generation is no longer invisible
- WECC has 3.7 GW of wind generation capacity
installed - Some areas are experiencing high saturation
levels - Significant expansion expected in the near future
- Adequate simulation models are indispensable
- Identify and address impact of new generator
additions - Perform planning studies to maintain system
reliability at the local and regional level - The Status Quo is not acceptable to WECC
- One-of-a-kind and proprietary models are
incompatible with the current system modeling
practice in WECC - Difficult and confusing for users
- Cannot be maintained in base cases once plant is
built
17Proposed standard models
- Based on characteristics of grid interface
- Type A conventional induction generator
- Type B wound rotor induction generator with
variable rotor resistance - Type C doubly-fed induction generator
- Type D full converter interface
Type A
Type B
Type C
Type D
18Technical challenges
- Wind generator modeling versus wind plant
modeling - Wind plant equivalencing is required to reduce
data and computational burden - WGMG will first concentrate on development of
generic WTG dynamic models - Grid versus wind disturbances
- Performance in response to grid disturbances can
be modeled reasonably well using generic models - Performance in response to wind disturbances
could introduce complications but note that
this is less importance in the planning
environment
19Technical challenges
- Single and multiple generator equivalencing
20Wind Generation Interconnection -Other Ongoing
Activities
- UWIG
- IEEE PES
- Power System Dynamics Committee Wind Gen. TF
- Other technical committees in process of
engaging - Wind Power Coordinating Committee established
under Technical Council (June 2005) - International
- Significant research ongoing
- Coordination with US efforts
- UWIG
- WECC
21Wind Integration Why the Concern?
- Wind generation is an attractive source of
electric energy - The electric power business is based on capacity
- System planning
- Reliability considerations
- Wind energy doesnt fit this model well
- Variability
- Uncertainty
- What are the financial consequences of these
attributes?
22What is Integration Cost?
- Does buying wind energy increase costs to serve
the remaining load? - Depends on the definition of buying
- Consensus that the qualitative answer is Yes
- Real question is How much?
- General Definition
- Increased cost of serving load not served by wind
- Can be evaluated by comparing wind to equivalent
energy source that imposes no incremental burden
on operations - Elements
- Conventional ancillary service regulation,
reserves etc. - Increased costs due to variability of wind
generation - Increased costs due to increased uncertainty in
unit commitment and scheduling - Possibly some costs due to the actual value of
energy delivered vs. the reference
23Dealing with Variability and Uncertainty
- We are accustomed to working with some degree of
variability and uncertainty - Variability
- Load varies by seconds, minutes, hours, by day
type, and with weather - Supply resources may not be available or limited
in capacity due to partial outages - Prices for power purchases or sales exhibit are
not constant - Uncertainty
- Operational plans are made on basis of best
available forecasts of needs some error is
inherent - Supply side resource available with some
probability (usually high)
Key Questions
- How does wind generation affect this existing
variability and uncertainty? - What are the costs associated with the changes?
- Can we maintain the integrity of the system under
these new conditions?
24Wind Generation Modeling Challenges
- Most of the wind generation yet to be built
- Expected geographic spread is substantial
- Neglecting transmission issues, control area
impacts are based on the behavior of the
aggregate wind generation, not individual plants - Supply resources are managed as a group to meet
load, maintain reliability and minimize cost - No one-to-X backups
A realistic representation of the wind generation
is critical to the study results
25Approach Re-creating the Weather
- Historical years (2000, 2002, 2003)
- Increased temporal and spatial resolution (5 km2,
10 min.) - Use historical data to initialize and guide
numerical weather model - Save important weather variables at points of
interest
26Baseline Data for Study
- Multiple years of 10-minute resolution data for
- System load (scaled to study year)
- Aggregate wind generation
- Load data wind generation data from corresponding
years - Allows a wide-rage of what if questions to be
addressed through simulations and calculations
27Low Correlation Period
28High Correlation Period
29Distribution of Hourly Changes(normalized)
Aggregate Production
Individual Plants
30General Findings from Studies to Date
- Good wind generation data is critical for
assessing power system impacts - Chronological, historical
- Relatively high resolution
- Long-term
- Represents geographic diversity
- Correlated with actual load
- Statistical and mathematical processing can help
identify operating challenges
Ramp up requirement increased by wind
Ramp down requirement increased by wind
31Variability and Uncertainty Examples
32Insights and Perspectives
- Geographic dispersion of wind plants
- Substantially reduces effects of shorter-term
wind plant output fluctuations - Major impacts seen at hourly level and with
short-term planning (unit commitment and
scheduling) - Wind generation forecasting can help to reduce
these impacts - Markets
- Access to liquid day-ahead and real-time markets
can reduce integration costs - Provide additional low- to modest- priced
resources for balancing and dealing with
uncertainty of wind generation
33Insights and Perspectives
- Wind Generation Modeling
- Meteorological simulations can provide
high-quality data for assessing impacts - Labor and computationally intensive, but superior
to alternative methods - Analytical Methods
- Statistical and mathematical techniques can
provide useful results more exhaustive
validation would be helpful - Chronological simulations of power system
operation are most straightforward (approach and
results understandable by widest range of
stakeholders) can be labor intensive and
relatively costly, however
34Status - Integration
- Assessment of Integration questions also
continues in the form of specific, focused
studies, e.g. - Xcel Energy Minnesota (integration cost study)
- Xcel Energy - Colorado (integration cost study)
- State of Minnesota (Dept. of Commerce)/Xcel RDF
- Sacramento Municipal Utility District
(prospective integration study) - CAISO/CEC (integration study related to RPS)
- BPA (shaping and firming services for wind
generation) - Manitoba Hydro (integration study)
- AESO (wind generation market impact assessment)
- Analysis techniques are becoming more
sophisticated and better accepted - High-fidelity chronological models of regional
wind scenarios - Detailed consideration of specific operational
practices or market rules - Application of power industry tools for analysis
35 Summary of Wind Integration Studies
Source UWIG
36Ongoing Wind Integration Studies in WECC
- EnerNex Studies
- Sacramento Municipal Utility District
- Public Service New Mexico
- Idaho Power
- Avista Corporation
- Public Service Colorado
- Others
- California Intermittency Project (GE, for the CEC
and CPUC) - Pacificorp (internal)
- Puget Sound PL (internal)
- Alberta Electric System Operator
37Public Service New Mexico on the tails of
the curve
- Operating challenges with wind generation
- Existing 200 MW plant has measurable effect on
control performance - More wind planned for control area
- PNM control area
- Small relative to existing wind
- General shortage of regulating resources
- Cannot purchase regulation service
- Large, concentrated wind plant has significant
impacts on CPS2
38Wind Generation and ACE
Source A. Ellis Public Service New Mexico
39High Resolution Simulations The Next Step
Areva TD eterra-simulatordispatcher training
environment
40Question How are Wind Generation Forecasts used
in Power System Operations and Planning ?
- Honest Answers
- Poorly, at the moment, and
- Were really not sure
- Forecasting experience in US
- Required by some more recent PPAs
- Little attention paid to requirements for use
- Motivation and incentives lacking
- Therefore, view is that wind generation forecasts
are of little value
41Value Propositions for Forecasting
- Economic
- Characteristics of wind generation - variability
and uncertainty are managed with minimum
financial impact to remainder of supply portfolio - Positive attributes e.g. correlation with load
or hydro inflows are leveraged - Security Reliability
- Performance of energy transportation and delivery
infrastructure is not compromised - Quality of electric service to customers is
maintained
42Nonetheless,
- Wind generation forecasting seen as key to
continued wind industry growth - Value of wind generation forecast being
demonstrated in some integration studies - e.g. NYSERDA study by GE
- 100 million annual forecast value
- Work beginning on next phase
- Testing of hypotheses
- Concepts to implementation
- Measuring performance and value, then fine tuning
- Significant Activities in U.S.
- XCEL Energy/MN RDF
- Evolution of CA PIRP forecasting program
- Various integration studies focused on use of
short-term wind generation forecasts in RT
operations
43Status Wind Integration Costs from North
American Studies
- A number of studies conducted over past five
years - More in progress
- Findings
- Total integration costs for modest penetrations
of wind generation (to 15 or 20) range from a
couple to 5/MWH of delivered wind energy - Costs due to planning uncertainty and hourly
variability seem to be most significant - Regulation costs are small
- Much work remains
- Forecasting impact/value
- Sensitivity of integration costs to resource
portfolio, operating practices - Market impacts
- Enhanced algorithms for planning with higher
uncertainty - Use of short-term forecast information in RT
operations
44Opportunities for Collaboration
- Wind issues are entering the power engineering
mainstream - Much to do
- Talent and resource applied to problems is
increasing steadily - IEEE PES is stepping up to the plate
- Wind Plant Dynamics Working Group (2004)
- Wind Power Coordinating Committee (2005)
- Utility Wind Integration Group (UWIG)
- Is currently the most active and relevant forum
for exchange of wind energy-related power system
information - Has taken on a more active role with formation of
working groups (2004) - Groups work to identify and address most urgent
questions regarding interconnection and
integration of wind turbines and wind plants
45UWIG Focus Areas and Topics
- Operating Impacts Users Group
- Methods for assessing operating impacts
- Wind energy forecasting
- High wind penetrations in a carbon-constrained
world - Wind generation capacity valuation methods
- Best practices for wind plant integration
- Modeling and Interconnection Users Group
- Wind turbine and plant models for dynamic
simulations - Generic models for interconnection screening
studies and base case models (WECC) - Short-circuit behavior of wind plants
46IEEE Power Energy , November 2005