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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
     Photo courtesy of PPM Energy
                                    Slide 1
NW Wind Integration Action Plan Summary
 NW added ~900 MW of wind in 2007, >2200 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
   – 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
                                                                 Slide 2
     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 @ 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.

                                                                Slide 3
Slide 4
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 add‟l 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
                                                                                 Slide 5
                                                              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
                         8200                                                                                                                    8200                                                                                                                   100

                         8100                                                                                                                    8100                                                                                                                    80

                         8000                                                                                                                    8000

                                                                                                                                                                                                                                              REGULATION IN MEGAWATTS
                                                                                                                        AREA LOAD IN MEGAWATTS


                                                                                                                    =                            7900

                                                                                                                                                                                                                                          +                              40


                         7700                                                                                                                    7700
                         7600                                                                                                                    7600
                         7500                                                                                                                    7500

                         7400                                                                                                                    7400

                         7300                                                                                                                    7300                                                                                                                   -100
                            07:00   07:20   07:40   08:00     08:20       08:40     09:00   09:20   09:40   10:00                                   07:00   07:20   07:40   08:00   08:20         08:40   09:00   09:20   09:40   10:00                                    07:00   07:20   07:40   08:00   08:20         08:40   09:00   09:20   09:40   10:00

                                                            Actual Load    Load Trend                                                                                                       Load Trend                                                                                                             Regulation

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

                                                                                                                                                                                                                                                                                                               Slide 6
                                    TOTAL WIND GENERATION IN THE BPA BALANCING AUTHORITY AREA (Control Area)
                                                            JAN-08, at 5-min Intevals
                        MAX 5-MIN RAMPS: +201 MW, -200 MW                                                                                                                                                                               MAX FOR MONTH: 1217 MW (Jan30)
     1300               MAX 30-MIN RAMPS: +398 MW, -314 MW
                        MAX 60-MIN RAMPS: +580 MW, -423 MW










































       Source: 5-min data via SCADA/PI for Pt. 79687                                                                                                           Date (fixed 5-min intervals)

                                                                                                                                                                                                                                                                                                                                                 Slide 7
                 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
 The 2nd slide shows the balancing required for simulated period for
  total wind of 2700 MW. Note the peak Balancing required.

                                                                Slide 8
Regulation versus Following (Wind Example)

                                     Slide 9
2700 MW Simulated Balancing Capacity Requirements

                2nd 3 week Period Simulation

                                               Slide 10
           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.

                                                                Slide 11
Schedule Vs. Actual – 12/27 – 12/29 2007

             <= Actual

     - Wind acts more like load - generation
     seldom matches schedule, and
     - Good hourly schedule will still increase
     Balancing Capacity requirements.

                                                  Slide 12
                                                 Example: Frequency Distribution of Wind Generation Variation
                                                                               10-MINUTE RATE OF CHANGE IN WIND GENERATION:
                                                                                       TOTAL WIND: SIX WEEKS IN 2008
                                                                                                    Total Wind Nameplate Gen = 5080 MW

Change in Wind Gen MW Over Rolling 10 Minutes







                                                         0%   5%   10%   15%   20%     25%    30%    35%    40%    45%    50%    55%    60%    65%   70%   75%   80%   85%   90%   95%   100%
                                                                                     Percent of Time with Rate of Change At or Above Plotted Value

                                                                                                                                                                                    Slide 13
      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

                                                                                             Slide 14
Slide 15
                        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.

                                                            Slide 16
               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
 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.

                                                              Slide 17
        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 WTG‟s 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

                                                                   Slide 18
            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

                                                             Slide 19
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

                                                          Slide 20
Dynamic Simulations - Malin 500-kV bus voltage


                                  2700 MW of
                                  Wind with No
                                  Voltage Control
                                  replaced 2700 MW of
                                  hydro + thermal

                                             Slide 21
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
     – 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

                                                             Slide 22
                   Voltage Control Types
            POI Voltage

                                  High Side Voltage Control

                                  VC with 7.5 % Reactive Droop

                                  VC with 15% Reactive Droop
Power Factor /                    ~ Low Side Voltage Control
VAR Control

             POI Reactive Power

                                                     Slide 23
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.

                                                              Slide 24
      Summary Wind Integration for BPA
 BPA continues to study a lot of wind interconnection requests
  (presently >9000 MW in study queue)
 Total ~1400 MW now interconnected and operating, may be
  3000+ MW by late 2009. Operation Challenges to be
    – 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
                                                            Slide 25

             Slide 26