Large Wind Integration Impacts on Operations

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Large Wind Integration Challenges for Operations
/ System Reliability
By Steve Enyeart, BPA With contributions
from Bart McManus, BPA Roy Ellis, BPA Dmitry
Kosterev 2/12/08 Photo courtesy of PPM Energy
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NW Wind Integration Action Plan Summary

• NW added 900 MW of wind in 2007, gt2200 MW Total
  now
• Total Wind in the NW Forecast 3500 - 3800 MW by
  end of 2009
• Northwest Wind Integration Forum formed to
  Address
• Transmission System Expansion and Funding
• Wind Integration Costs and Cost Shifts from Load
  to Wind Generation
• Operating Issues including Regulation and Balance
  of Hour
• A Regional Wind Forecasting System
• ACE Diversity Interchange and other Control Area
  sharing ideas to increase flexibility for Wind
  Integration
• Severe Wind Ramps Impact on Reliability

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Impact of State RPS Requirements

• Montana, Washington, and Oregon have implemented
  Renewable Portfolio Stds
• According to the estimates from the NW Power
  Council
• Oregon 15 by 2015 - 650 aMW, 25 by 2025
• Washington 7.5 by 2015 672 aMW, 15 by 2020
• Wind is the primary Renewable Resource at this
  time
• Assume 1400 aMW _at_ 30 equals 4700 MW peak
  capacity. This and export of 2000 MW would be
  7, 000 MW by 2015.
• BPA has provided interconnection for 3500 MW at
  various locations and Rock Creek, John Day 500 kV
  interconnects (1200 MW each).
• Other NW Utilities have connected over 800 MW
  with plans for more.

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Wind Gen. within BPA Control Area (BAA)

• BPA integrated 650 MW in 2007, total 1400 MW,
  may be 3000 MW by late 2009
• Queue requests exceed 10,000 MW under study (due
  in part to BPA transmission location relative to
  wind resources)
• Present 1400 MW, 15 of 9000 MW Peak BPA Load,
  higher than any BAA in US.
• BPA Addressing
• Intra-hour increases in total Balancing
  requirements
• Impact of severe wind ramps on Balancing Capacity
  
• Cost/Cost Shift of addl Balancing Capacity
• Need for Voltage Support, Dynamic VAr
• Balancing within 1 Minute Regulation (AGC
  response) Load Following for balance of hour
  schedule see next slide

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Within Hour Balancing Definitions

• Regulation minute-minute difference between
  generation and load (AGC).
• Following is defined as the change in the general
  trend over a specific time interval 5, 10, 15 or
  even 60 minutes.
• Within-Hour Balancing Load Following
  Regulation

Within Hour Balancing defined as the with-in hour
generation adjustments for variances of Load /
variable (wind) Generation New Requirement for
Wind Generation
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Wind Balancing Analysis

• As previous slide demonstrates, Wind Generation
  is quite variable, impacting BAA Balancing and
  total AGC Capacity Requirements.
• The next slide shows the balancing required for a
  recent large wind ramp. Not nearly as extreme as
  the previous slide would have implied.
• The 2nd slide shows the balancing required for
  simulated period for total wind of 2700 MW. Note
  the peak Balancing required.

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Regulation versus Following (Wind Example)
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2700 MW Simulated Balancing Capacity Requirements
2nd 3 week Period Simulation
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Wind Balancing Analysis (Cont.)

• The next slide shows the problems with scheduled
  vs actual (even with hourly adjustments) Note
  that scheduled trails actual and misses peaks and
  valleys.
• This increases Within-Hour Balancing reserves
  requirements.
• Better forecasts would reduce this problem.
• The 2nd slide is Frequency Distribution Analysis
  for total Balancing Capacity requirements
  assuming 5000 MW.

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Schedule Vs. Actual 12/27 12/29 2007
lt Actual
Note - Wind acts more like load - generation
seldom matches schedule, and - Good hourly
schedule will still increase Balancing Capacity
requirements.
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Example Frequency Distribution of Wind
Generation Variation
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Wind Within-Hour Balancing Analysis

• The next slide BPA estimates the increase in
  Balancing Capacity required for up to 2880 MW.
• Cumulative Frequency Distribution method used to
  calculate increase in Balancing Capacity,
  assuming 97.5 of Regulation and 95 Balance of
  Hour events are covered.
• The Tail events from the previous slide
  indicate that some wind ramps could exceed
  Balancing Capacity. Options include
• Increase Balancing Capacity More cost to all
  wind farms
• Wind Ramp Controls to limit severe ramps
• Other BA tools like shared ACE
• Analysis includes using locations of proposed
  wind sites in BPA queue to provide simulation of
  locational diversity.

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Wind Ramps

• Wind Ramps are large unscheduled changes in the
  output of a wind farm or the aggregate of all
  wind farms in a Control Area.
• As seen above Wind increases Balancing Capacity
  Requirements.
• BPA now Concerned for Reliability Impacts (CPS2
  Violations).
• Late fall 2007 BPA experienced increase in
  within-hour Balancing due to wind. CPS2
  Violations are also increasing.
• Wind Ramp Controls now considered necessary and
  may be implemented in some form in the next year.

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Improved AGC Response

• Improving the AGC response to deviations of the
  load-generation balance due to wind generation is
  one option to reducing overall wind integration
  costs.
• BPA Proposal Modify AGC Algorithm (Feed
  Forward AGC)
• Present AGC Actual Load Scheduled Generation
  (includes Wind schedules)
• New AGC Load Forecaster Scheduled Generation
  Forecasted Wind Generation
• Goal is to anticipate AGC response, reduce
  overshoot, cycling of units (wear and tear) and
  minimize generation on stand-by.
• Load Forecaster module to also be included in
  FF AGC.

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Wind Forecast Module for FF AGC

• Develop 5 minute within-hour wind generation
  forecasts enhanced with weather and regional
  monitoring of wind generation.
• Uses Data (MW, wind speed, direction, unit
  status) from WTGs in Wind Farm, from all wind
  farms in BAA
• Other goals
• Provide output to adjust FCRPS generation
  schedules (mid-hour adjustment), reducing AGC
  units on stand-by or set aside for AGC.
• Provide mechanism to automate Wind Ramp Limits
  control if Balancing reserves below minimum
  capability (next 10 30 minutes).
• Pilot Project underway with 3-Tier to provide
  Forecasts
• Target Mid 2009 to have Pilot FF AGC implemented

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BPA Wind Integration Rate

• Traditionally Loads have paid for regulation and
  load following as generation deviations were rare
  not so for wind.
• BPA held Public workshops to develop a new Wind
  Integration Rate for within-hour balancing.
  (Public review still underway).
• Rate to be applied to Wind Generation
• Rate to be effective for a one-year period, FY
  2009
• Rate will be based on installed capacity during
  rate period
• Assumes 2240 MW up to 2880 MW in BPA Control Area
• Estimates up to 23M needed for FY09 rate period

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Wind Farm Dynamic Voltage Performance

• Early WTG designs were mostly induction machines
  (used switched caps for PF correction)
• Voltage control was limited to switched Caps on
  34.5kV bus
• Integration of large amounts of wind generation
  requires dynamic reactive control capabilities
• Need to match Synchronous Machines performance to
  maintain system performance and line loadings.
• Next slide compares effect of 2700 MW of wind on
  grid without Dynamic VAr support to synchronous
  generation response

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Dynamic Simulations - Malin 500-kV bus voltage
Baseline 2700 MW of Wind with No Voltage
Control replaced 2700 MW of hydro thermal
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Wind Farm Voltage Controller Requirements

• Voltage control of wind farms required to provide
  primary voltage support for system events.
  Options include
• High side Voltage Control (may be overly
  sensitive)
• Low side Voltage Control (may be too insensitive
  for system response)
• Line Drop reactive compensated Voltage Control
  (Qdroop)
• Line Drop adjustable up to15 (mid-line subgrid
  applications), for 7.5 typical applications
  allows for fine tuning of VC.
• Next slide demonstrates Line Drop options

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Voltage Control Types
POI Voltage
High Side Voltage Control
VC with 7.5 Reactive Droop
VC with 15 Reactive Droop Low Side Voltage
Control
Power Factor / VAR Control
POI Reactive Power
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Wind Farm Dynamic Performance Summary

• For Large Wind Generation BPA Requires -
  Controllable Dynamic VAr devices required (either
  WTG or DVAr devices)
• Voltage control mode required (no PF control) to
  provide primary voltage support for system events
• Type of voltage control depends on application,
  but Line Drop compensation preferred for
  flexibility of Application.
• Smaller Wind farms or those in mid-line or remote
  areas will still need to be evaluated on
  case-by-case basis.

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Summary Wind Integration for BPA

• BPA continues to study a lot of wind
  interconnection requests (presently gt9000 MW in
  study queue)
• Total 1400 MW now interconnected and operating,
  may be 3000 MW by late 2009. Operation
  Challenges to be Addressed
• Regulation/Balance of Hour AGC/reserve
  requirements are increasing and are being
  addressed with new rate
• FF AGC should reduce impact and cost of Wind in
  BAA
• Wind ramp controls may be needed for Reliability
• Dynamic VAr for Voltage control needed to
  maintain system capacity and reliability

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Questions?