Optimizing Wind Generation in ERCOT Nodal · PDF fileOptimizing Wind Generation in ERCOT Nodal Market ... –Wind-powered Generation Resource Production Potential ... ±1.875*16 =

Optimizing Wind Generation in ERCOT Nodal MarketResmi Surendran – ERCOTChien-Ning Yu – ABB/VentyxHailong Hui – ERCOT

FERC Conference on Increasing Real-Time and Day-Ahead Market Efficiency through Improved Software - June 23-25, 2014

FERC Conference on Increasing Real-Time and Day-Ahead Market Efficiency through Improved Software

June 23-25, 2014 2

• Overview of ERCOT – Wind in ERCOT

– Operational Challenges

• Wind Scheduling in ERCOT Nodal Market– Day-Ahead Market (DAM)

– Reliability Unit Commitment (RUC)

– Real Time Market (RTM)

• Improvements due to better handling of wind

• Summary

Agenda


June 23-25, 2014 3

• 85% of Texas load– 24 million consumers

• 40,530 circuit miles of high-voltage transmission

• 74,000 megawatts (MW) capacity for peak demand – From 550 generation resources– With 8.7 % Wind capacity included– 11,059 MW Wind Capacity

• 68,305 MW peak demand (Aug.3, 2011)– Peak Wind 10,296 MW (March 26 , 2014)

• $33 billion Market– ~1,100 active Market entities

• 73% of load are competitive-choice customers– 179 competitive retailers

• Nodal market completed three year of operation on Dec. 1, 2013

• Extensively working on ensuring Resource Adequacy

ERCOT


June 23-25, 2014 4

ERCOT Wind Generation

3,110

7,3058,131

8,631

116816 977 1,173 1,385

1,854

2,875

4,785

8,005

8,9169,400 9,604

10,407

11,065

14,169

18,364

19,190 19,690

0,000 MW

5,000 MW

10,000 MW

15,000 MW

20,000 MW

25,000 MW

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

Cumulative MW Installed Cumulative Planned (Signed IA)

The data presented here is based upon the latest registration data provided to ERCOT by the resource owners and can change without notice. Any capacity changes will be reflected

in current and subsequent years' totals. Scheduling delays will also be reflected in the planned projects as that informationis received.

This chart reflects planned units in the calendar year of submission rather than installations by peak of year shown.

ERCOT Wind Installations by Year

(as of April 2014)





(as of April 2014)





(as of April 2014)





(as of April 2014)

11,059

Target

MW

Target

Yr

Achieved

Yr

2000 2010 2005

5000 2015 2007

10000 2025 2010


June 23-25, 2014 5

• 11,059+ MW of installed wind capacity

– Significant amount of additional MWbeing reviewed

• Wind generation record of Peak Wind10,296 MW (March 26 , 2014)

– 29% of system load

• Improved transmission, market rulesand operator tools allowed moreenergy from wind to be generated

ERCOT Wind Generation


June 23-25, 2014 6

Wind Pattern in ERCOT


June 23-25, 2014 7

Wind Pattern in ERCOT

ERCOT Wind Generation vs. System Load on a typical peak day


June 23-25, 2014 8

• Inadequate transmission for projected wind growth

• Constraint management under high and low wind

• Higher frequency deviations due to large system excursions

• Difficulty in managing transient stability due to reduced inertial response

• Increased variability of net load

• Higher Ancillary Service Requirement– Increased Non-Spin for forecast error of net load

– Increased Regulation due to increased net load variability

• Increased volatility in prices– Lower average system wide energy prices

– Lower average Real Time prices in West Zone

– Higher Day-Ahead premium in West Zone

Operational Challenges due to High Wind


June 23-25, 2014 9

• Wind Forecasts

– Hourly forecasts for a rolling 48-hour in both system level and individual Wind-Powered Generation Resource (WGR) level

– Total ERCOT Wind Power Forecast (TEWPF): • probability distribution of the hourly production potential from all wind-power in

ERCOT for each of the next 48 hours

– Short-Term Wind Power Forecast (STWPF): • 50% probability of exceedance forecast

– Wind-powered Generation Resource Production Potential (WGRPP): • 80% probability of exceedance of the TEWPF

• Current Operating Plan (COP)– Anticipated operating conditions for next seven Operating Days

– WGRs are required to keep High Sustained Limit(HSL) in COP updated to less than or equal to the most recent STWPF for the first 48hrs

Wind Input to ERCOT Markets


June 23-25, 2014 10

• The QSE representing WGRs may participate in DAM for wind scheduling by submitting one of the following offers or bids in DAM:

– Three-Part Supply Offer to sell energy for the physical WGR

– Virtual Energy Only Offers to sell or Bids to buy at the WGR Settlement Point

– CRR Point to Point (PTP) Obligation Bids with source or sink at the WGR

Settlement Point

• Physical offers are cleared based on HSL from COP

Wind in Day-Ahead Market


June 23-25, 2014 11

• WGRs are required to participate in RUC by submitting a valid COP

• The full capacity up to HSL of WGR is considered available to be dispatched in RUC

• WGRPP value used in the RUC for each WGRs is considered the available capacity of the WGR when determining capacity-short RUC charges, regardless of the real-time output of the WGR

Wind in Reliability Unit Commitment


June 23-25, 2014 12

Wind Scheduling in DRUC

2,000

2,500

3,000

3,500

4,000

4,500

5,000

5,500

6,000

6,500

7,000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

MW

Hour

DRUC WGR COP HSL STWPF WGRPP RT Wind


June 23-25, 2014 13

• Optimize the Phase Shifter tap in DAM/RUC– Initially used fixed tap position for each hour for each Phase Shifter based on the

WGR forecast and system load condition 2 days ahead of operating day

• Hourly absolute phase shifter tap positions are modeled as control variables in the optimization engine of Security Security Constrained Unit Commitment (SCUC)

• Shift factor of phase shifters with respect to the transmission constraint is defined as MW/tap– i.e. the MW flow change on the constraint with respect to each tap position

change

• Cost function of phase shifter tap position is modeled as a cost of tap position changes to the initial position

Improvements in DAM/RUC for Wind


June 23-25, 2014 14

• Majority of the Phase Shifter in ERCOT relieves transmission overloads caused by variations in wind generation

• The maximum degree change for each of the phase shifters is ±1.875*16 = ±30 degree

• Optimization of these phase shifter tap positions helped remove unrealistic congestion in DAM and RUC

Phase Shifters in ERCOT


June 23-25, 2014 15

• RTM re-dispatch generation every 5 minutes based on current WGR output to take care of net load variability

• RTM issues WGR specific curtailment instruction for managing congestion

• WGRs are required to

– follow Base Points if the curtailment flag is set and

– automatically release from curtailment under low frequency

• WGRs are charged a fine if they generate more than 10% of their Base Point when they are curtailed unless it is aiding frequency

Wind in Real-Time Market


June 23-25, 2014 16

• In Real-Time, WGRs are required to

– offer in their full capacity

– telemeter HSL equal to current net output of the facility

– limit its ramp rate to 20%per minute of its nameplate rating as registered with ERCOT when responding to or released from an ERCOT deployment

– limit its ramp rate to 25%per minute of its nameplate rating as registered with ERCOT anytime

Wind in Real-Time Market


June 23-25, 2014 17

• If a Wind Generation Resource did not submit Energy Offer Curves in Real-Time Market, SCED market clearing engine will create a Proxy Offer Curve for it

Real Time Proxy Offer Curve for Wind Resources


June 23-25, 2014 18

Typical Wind Aggregated Energy Offer Curve

-300

-250

-200

-150

-100

-50

0

50

0 500 1000 1500 2000 2500 3000 3500 4000

En

erg

y O

ffe

r C

urv

e P

ric

e (

$/M

Wh

)

Energy Offer Curve MW

Energy Offer at 2AM Energy Offer at 5PM


June 23-25, 2014 19

• Implemented a flag to indicate when a WGR was curtailed

• Initially WGRs were required to

– Set HSL to current net output capability after each RTM run and hold it constant until the next RTM run

– consider the WGR as curtailed if the base point from RTM was less than HSL minus 2 and not curtailed if base point from RTM was greater than HSL minus 2

• Changed to

– Telemeter HSL as current net output capability all the time

– Consider as curtailed and follow Base Point if the curtailment flag is set

Improvements in RTM for Wind


June 23-25, 2014 20

System Wide Wind Generation Curtailment

0

100

200

300

400

500

600

700

800

4000

4500

5000

5500

6000

6500

7000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Win

d C

urt

ail

men

t (M

W)

Win

d G

en

era

tio

n (

MW

)

Hour

Base Point Telemetry MW HDL Curtailment MW


June 23-25, 2014 21

Real Time Curtailment of Single Wind Resource

0

1

2

3

4

5

6

7

8

9

10

0

20

40

60

80

100

120

140

160

180

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Cu

rtail

Fla

g

Win

d G

en

era

tio

n (

MW

)

Hour

Base Point Telemetry MW HDL Curtailment Flag


June 23-25, 2014 22

• The Nodal Real-Time Market design has resulted in more stable frequency control

• The Graphs illustrate an observed 2000 MW drop in wind under both designs:– Under the Zonal design the

frequency fluctuated ± 0.08 Hz

– Under the Nodal design the frequency fluctuated ± 0.04 Hz

Enhanced Ability to Manage Volatility

Wind Ramp in Zonal

Wind Ramp in Nodal


June 23-25, 2014 23

ERCOT’s recent NERC CPS1 scores shows control improvements

Better Frequency Control Performance

CPS1 12 Month Rolling Average = 163.30%


June 23-25, 2014 24

• Texas continues to explore more wind power capacity – more than 11,000 MW of commercial wind power capacity installed

– nearly 8,000 MW of new projects in development

– more than 26,700 MW under study.

• Special rules and system improvements made for wind generation resources resulted in better utilization of the available wind capacity while maintaining reliability– Running RTM every 5 min based on current Wind Resource production

– Proxy offers at -$250,

– WGR specific curtailment signals,

– Requiring WGRs to follow Base Point and implementing deviation charges

– Putting ramp restrictions

– Requiring WGRs to provide primary frequency response

– Phase shifter tap optimization,

Summary


June 23-25, 2014 25


June 23-25, 2014 26

Appendix


June 23-25, 2014 27

Wind Generation in U.S.

Source: www.awea.org

Documents

Optimizing Wind Generation in ERCOT Nodal · PDF fileOptimizing Wind Generation in ERCOT Nodal Market ... –Wind-powered Generation Resource Production Potential ... ±1.875*16 =