11 LSWI operations and markets

Power Systems & Energy Course

Large-Scale Wind
Integration:
Power System Operations

Jason MacDowell


Overview of Power
System Operations

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2


Impact of High Wind Penetration on
System Operation and Power Markets
• Emerging issue in many parts of the world as wind power becomes
a significant portion of the overall generation mix
• Many lessons learned in Europe (painful but valuable)
• Discuss results from detailed analysis of several regions in North
America (mostly from Western USA, New York, and California)
• Share ideas on how to evaluate and quantify the impact of wind
power on the overall power grid
• Share lessons learned – and advice looking forward
• Start with basic concepts of grid operation and how wind power
fits in

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3


What is a Control Area?

FERC Definition

An electric power system or combination of electric power
systems to which a common automatic control scheme is
applied in order to:
• match, at all times, the power output of the generators
within the electric power system(s) and capacity and
energy purchased from entities outside the electric power
system(s), with the load in the electric power system(s);
• maintain, within the limits of Good Utility Practice,
scheduled interchange with other Control Areas;
• maintain the frequency of the electric power system(s)
within reasonable limits in accordance with Good Utility
Practice; and
• provide sufficient generating capacity to maintain
operating reserves in accordance with Good Utility
Practice.

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5


Control Area Obligations
• Meet its area instantaneous demand, Interchange Schedule,
Operating Reserve, and reactive resource requirements.
• Provide its frequency bias obligations.
• Balance its Net Actual Interchange and Net Scheduled
Interchange
• Use tie-line bias control (unless doing so would be adverse to
system or the Interconnection reliability).
• Comply with Control Performance and Disturbance Control
Standards
• Repay its Inadvertent Interchange balance.

How is this done?
How are grid operations affected by wind power?
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6


California Load – Average Day in July 2003
50

Load
45

45

40

40

35
Cumulative MW

35

GW

30
25
20

Gas Turbine
Variable Imports
Pump Storage Hydro
Hydro

30
Combined Cycle

25
Fixed Imports

20
Steam

15

15

10

10

Biomass
Geothermal

5

5

0

0
0

6

Hour

12

18

Nuclear

More Flexible for Dispatch

50

24

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7


System Operation Process - Overview
Day Ahead
•
•
•

Prepare load forecast (Total MW load for each hour of the day)
Commit units that will run to serve the load (accounts for uncertainty)
Preliminary dispatch schedule for each unit (by hour)

Units with long startup times are “committed” for operation during the next day

Hour Ahead
•
•

Perform hour-ahead load forecast
Adjust hourly dispatch for committed units as required to match actual load

Real Time
•
•
•

Load-following (typically, dispatch is adjusted at 5-minute intervals)
Adjustments based on “economic dispatch”, using marginal costs or competitive
bids
Regulation (fast adjustments of MW to regulate frequency and intertie power
flows)

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8


Conceptual Timeline for Day-Ahead Unit Commitment
Day of Operation
35

Load

GW

30
25
20
15
-24

5 am
Load + Unit
Data Received

12 am

-18

-12

-6

Hours

0

12 pm

12

5 am
Morning
Load Rise

11 am
Unit Commitment
Completed
SCUC

6

12 am

18

24

8 pm
Peak Load

12 pm

12 am

GFS
Updates
(6-hr period)

Wind
Forecast
29 hrs
44 hrs
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9


What happens when Wind Generation is Added?
Note that this example
assumes a large amount

of wind generation

50
Load
Wind

45
40
35

12.5 GW wind
generation on a system
with about
55 GW peak load

GW

30
25
20
15
10
5
0
0

6

12
Hour

18

24

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10


What happens when Wind Generation is Added?
50
Load
Wind

45

45

40

40

35
Cumulative MW

35

GW

30
25
20

Gas Turbine
Variable Imports
Pump Storage Hydro
Hydro

30
Combined Cycle

25
Fixed Imports

20
Steam

15

15
Biomass

10

10

5

5

0

0

Geothermal

0

6

12
Hour

18

Nuclear

Not Very
Maneuverable

50

More
Maneuverable

GT Peaker

24

Wind
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11


For grid operations, wind is “similar” to load .
50

• Like load, wind can be forecast a day
ahead

45

• Grid operators can plan day-ahead
operations base on a load forecast and
a wind generation forecast

• Uncertainty in the wind forecast adds to
the uncertainty in the load forecast
• Adjustments are made using hourahead forecasts and real-time data

40
35
30
GW

• Dispatchable generation is allocated to
serve the net of the forecast load minus
the forecast wind

Load
Wind
Load - Wind

25
20

Net Load
= Load Minus Wind

15

(This is what must be served
by other types of generation)

10
5
0
0

6

12

18

24

Hour

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12


Dispatchable Generation Serves “Net Load”
50

Load
Wind
Load - Wind

45

45

40

40

Wind

35
Cumulative MW

35

GW

30
25

Variable Imports
Pump Storage Hydro
Hydro

30
Combined Cycle

25
Fixed Imports

15

20
Net Load
= Load Minus Wind 15

10

10

5

5

0

0

20

Gas Turbine

Steam
Biomass
Geothermal

0

6

12

18

Nuclear

Not Very
Maneuverable

50

More
Maneuverable

GT Peaker will not run,
unless big forecast error

24

Hour
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13


Contingency and
Operating Reserves
Critical to Power System Operational Security

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14


Contingency and Operating Reserves
Contingency Reserves
•

MWs to cover for the loss of the largest unit (185 MW Coal Unit)

Operating Reserves
•
•

MWs to cover for the variability of wind and solar
Spinning Reserves + Non-spinning Reserves

Spinning Reserves
•

Available headroom (MWs) from committed thermal units

Non-Spinning Reserves
•
•

Available MW capacity from quick-start units
These units can be started in less than an hour

Total Reserves = Contingency Reserves + Operating Reserves

Island of Oahu
Contingency Reserves = 185 MW
Spinning Reserves = Committed thermal units
Non-Spinning Reserves = W9, W10, DG, CT1
(if not already committed)

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Reserve Requirements
• Industry is still learning about reserves
• Following example from an approximately
1500 MW system with a few very large wind
and solar PV projects….

Reserves for Wind
Development of Study Cases and Data

Wind Data
Lowest wind tends to be
late afternoon in the
summer

Highest wind tends to be
early hours in fall and
winter

Actual wind power output for year 2019 averaged over each hour for each month

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Reserves for Wind
Determination of Additional Reserve Requirements due to Wind and Solar

Wind Variability and Reserves
•Variability depends MW level… at medium to high wind speeds, generation and
variability high
•However, at higher wind speeds, variability is low since generation is maxed using
pitch control

Wind Reserve Determination Methodology
•

∆P = Difference between successive 10 min actual Wind output

•

Wind plant output divided into 30 MW bucket

•

Standard deviation of ∆P (Sigma delta P) within each bucket of MW output

•

Curve fit to approximate relationship between MW Output and Sigma Delta P

•

Curves are used with hourly day-ahead forecast of MW output to forecast hourly
Sigma Delta for next day

•

Amount of reserves carries is 2.5*Sigma Delta
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Reserves for Wind
Determination of Additional Reserve Requirements due to Wind and Solar
Expected wind reserve
patterns track average
expected production

Average reserve requirement due to wind for each hour for each month

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Reserves for Wind
Determination of Additional Reserve Requirements due to Wind and Solar

Contingency Reserve Requirement

TOTAL Reserve Requirement = Reserve requirement due to Solar + Reserve
requirement due to Wind + Contingency Reserve Requirement + 30 MW

20

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Grid Operations with
High Penetration of Wind
and Solar Power
Examples from

NREL’s Western Wind and Solar
Integration Study
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21


Western Wind and Solar Integration Study
Scenario Overview

Wind and Solar Combinations (% Energy)
Baseline:

Existing Wind and Solar Generation

10% In-Area: 10% Wind, 1% Solar In Footprint
10% Wind, 1% Solar Out of Footprint
20% In-Area: 20% Wind, 3% Solar In Footprint
10% Wind, 1% Solar Out of Footprint
30% In-Area: 30% Wind, 5% Solar In Footprint
20% Wind, 3% Solar Out of Footprint
Solar Mix:

•

70% Concentrating Solar Plant with Storage
(CSP w/S)

•

30% Photo-voltaic (PV)

Three SCENARIOS
•

In-Area (IA): Wind and Solar energy targets met
with in-state resources

•

Mega-Project (MP): Uses best sites in the footprint;
Wyoming has best wind.

•

Local-Priority (LP): Halfway between IA and MP.

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22


th, Study Footprint, No Wind
Week
of
July
10
Study Area Dispatch - Week of July 10th - No Wind
70,000

60,000

Hydro
Combined Cycle

Gas Turbine

50,000

MW

40,000

30,000

20,000

10,000

0
MON JUL 10

Nuclear

Steam Coal

Wind

Solar CSP w/ Storage

Solar PV

Combined Cycle

Gas Turbine

Pumped Storage Hydro

Hydro

TUE JUL 11

WED JUL 12

THU JUL 13

FRI JUL 14

SAT JUL 15

SUN JUL 16

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23


th, Study Footprint, 10% Wind
Week
of

July
10
Study Area Dispatch - Week of July 10th - 10%R
70,000

Less GT
60,000

50,000

MW

40,000

30,000

20,000

More Wind

10,000

0
MON JUL 10

TUE JUL 11

WED JUL 12

THU JUL 13

FRI JUL 14

SAT JUL 15

SUN JUL 16

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24


th, Study Footprint, 20% Wind
WeekStudy
of July
10
Area Dispatch - Week of July 10th - 20%R
70,000

Less Combined Cycle

Less GT

60,000

50,000

MW

40,000

30,000

20,000

10,000

0
MON JUL 10

TUE JUL 11

WED JUL 12

THU JUL 13

FRI JUL 14

SAT JUL 15

SUN JUL 16

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