Dispatch Technical Working Group Summary (Updated) - IESO

Dispatch Technical Working Group
Summary
Dispatch Technical Working Group (SE-91)
September 5, 2012

Overview
• Review of Dispatch Technical Working Group
design decisions
– Dispatch Data and Technical Limitations
– Dispatch Scheduling Process
– Compliance Deadbands
– Market Schedules
– Congestion Management Settlement Credits
– Tie-breaking
– Forecast reports
• DTWG Design Summary Document and Market
Manuals 2

Dispatch Technical Working Group
• DTWG was formed to address questions arising
from the Dispatching Variable Generation
Resources discussion paper relating to:
– Dispatch data
• Price/Quantity pairs
• Ramp rates
• Technical limitations
– Dispatch mechanics
– Compliance to dispatch instructions
– Congestion Management Settlement Credits (CMSC)
• Additionally, the issue of tie-breaking was
introduced to address impacts of floor prices
3

Dispatch Data Requirements

Dispatch Data - Offers
Are two price/quantity pairs sufficient to capture price
sensitivity over the entire operating range of a variable
generator?
• Wind generators indicated that they have a technical preference
against shutting down turbines, which occurs below approximately
10% of available output
– a minimum of two laminations would be required to reflect price sensitivity for
this technical preference
• Solar generators did not express a price sensitivity over their
operating range
• To allow for the integration of forecast data, PQ pairs should reflect
price sensitivity up to the available capacity of the generator
Decision: Variable generators will have the ability to submit up to 20
price/quantity pairs
5

Dispatch Data – Ramp Rates
Do wind and solar generators require the ability to submit ramp
rates and break points? Should the IESO assume a common
ramp rate for variable generators as dictated by fuel type?
• In Ontario, ramp rates vary from facility to facility
• Solar generators indicated that ramp rates can vary at a facility
depending on output level
• No need to restrict variable generators ability to submit ramp rates
and break points
Decision: Variable generators will have the ability to submit up to 5
ramp rates (up and down) and break points
6

Dispatch Data – Technical Limitations
What technical limitations exist for wind and solar generators
that must be respected by the dispatch algorithm in order to
produce a viable dispatch instruction that can be followed?
• The only technical limitation identified by DTWG members was
the preference of wind generators to minimize the need to shut
down individual turbines
• Wind generators indicated that this could be achieved through
dispatch data
Decision: No new technical limitations will need to be registered for
variable generators
7

Dispatch Scheduling Process

Forecast
(Hourly, 5minute)
Dispatch
Scheduling
Forecast to Dispatch
Submission of dispatch data will be as follows:
• Market participant (MP) will be responsible for
submitting offers to reflect price sensitivity
• Offer will be comprised of up to 20 price-quantity
pairs ($/MWh) and up to 5 up/down ramp rates
(MW/min).
• In the Day-Ahead Commitment Process (DACP) and
pre-dispatch, IESO will economically schedule to
respect the lesser of:
• the offered quantity;
• the hourly forecast; or,
• any submitted derates.
• In real-time, the IESO will use the 5-minute forecast as
well as submitted offers and derates.
9

MIO
Dispatch Data
DSO DAOS
Predispatch
DACP
Forecast to Dispatch (cont’d)
• Dispatch data used as input to Dispatch
Scheduling Optimizer (DSO) for Multi-
Interval Optimization (MIO), DACP and
pre-dispatch solutions.
• Pre-dispatch algorithm and DACP will
recognize forecast value as a constraint
(in both Market Schedule and
Constrained Schedule) and variable
generators are scheduled identically to
other dispatchable resources.
• In real-time, variable generators will
differ from other dispatchable resources
in both the initialization of the MIO
dispatch algorithm as well as the
content of the dispatch instructions.
10

• 5-minute forecast will:
5 Minute Forecast
Background
– Be available for each dispatchable variable generator
– Be updated every 5-minutes
– Span a rolling 24 intervals (2 hour time horizon)
• Dispatch Scheduling Optimizer (DSO) will
utilize the 5- minute forecast as an input for both
real-time sequences for dispatch and pricing
purposes

Constrained
sequence for
Interval 3
commences
Unconstrained
sequence for
Interval 3
commences
12:05
12:10
5-minute Forecast
Constrained vs. Unconstrained
For Interval 3:
• The constrained sequence will utilize the most recent 5
minute forecast received in advance of 12:05 to
determine dispatch
• The unconstrained sequence will utilize the most
recent 5 minute forecast received in advance of 12:15 to
determine market schedule
12:15
12:20
(INT 2) (INT 3) (INT 4) (INT 5)
12:25
12

5-minute Forecast
Reporting
• Market participant facility-specific reports will
be made available hourly and will:
– Be confidential to the market participant; and
– Include the 12 interval forecasts utilized by the
unconstrained sequence for the previous hour
• After the fact, public reports will use an average
of the most-recent 5-minute forecast for each
interval to determine an hourly value

Dispatch
Instruction
(Message Exchange)
5-minute Forecast
MIO
Dispatch
Advisories
(Web Reports)
Multi-Interval Optimization:
Use of 5-Minute Forecast
• MIO optimizes 5 critical
intervals selected from up to 11
future intervals.
• MIO produces a dispatch
instruction for the next interval
and dispatch advisories for an
additional 4 critical intervals.
• For the dispatch interval, the
variable generators most recent
5-minute forecast is the basis
for determining dispatch
instructions.
• Advisories will use the most
recent 5-minute forecast values
for those intervals
14

If an economic or security
constraint exists on the system, the
variable generator may be
required to change its output.
• The dispatch instruction will be sent
to the variable generator and the
new target output will be based on
the constrained solution (limited by
5-minute forecast quantity).
• Dispatch instruction will include a
new piece of information
(“Obligation Indicator”) which will
tell the Market Participant that the
instruction is mandatory
• MIO advisories will also include
Obligation Indicator
Dispatch Obligation: Mandatory
MIO
Dispatch Instruction
VG is uneconomic or security constrained
Target Output
Constrained
Solution
Dispatch
Instruction is
Mandatory
15

• The dispatch instruction must be
followed to mitigate the economic or
security constraint.
• Market participant must comply
with a mandatory dispatch
instruction unless doing so would
endanger the safety of any person,
damage any equipment, or violate
any applicable law.
• If the mandatory dispatch cannot be
followed, the IESO must be notified
immediately in order to take
alternate steps to mitigate the
situation.
Dispatch Obligation: Mandatory
(cont’d)
MIO
Dispatch Instruction
VG is uneconomic or security constrained
Target Output
Constrained
Solution
Dispatch
Instruction is
Mandatory
16

In the absence of an economic or
security constraint, variable
generators will generate
according to their available fuel
conditions.
• In the first interval following a
mandatory dispatch instruction, in
which the constraint no longer
exists, the Obligation Indicator will
indicate a “Release” from
constrained dispatch
• “Release” will only be sent once
the variable generator is capable of
ramping to its forecast quantity
• Following the “Release”,
subsequent forecast-based dispatch
instructions will not be sent
Dispatch Obligation: Release
MIO
Dispatch Instruction
VG is economic and not security constrained
Dispatch Target
based on
Forecast
Obligation
Indicator is
“Release”
17

In the absence of an economic or
security constraint, variable
generator will generate
according to their available fuel
conditions.
• 5-minute forecast will determine
the dispatch when the variable
generator is economic and no
security constraint exists.
• Forecast quantities for future
intervals will be used to develop
MIO dispatch advisories
• In steady state conditions, forecastbased
dispatch instructions will
not be sent to variable generators
Dispatch Obligation
(cont’d)
MIO
Dispatch Instruction
VG is economic and not security constrained
Dispatch Target
based on
Forecast (not
sent to VG)
18

Dynamic data
telemetered DSO
Solution every 4
seconds
VG
Manual
Dispatch
IESO Communication
Manual Dispatch
• Events may occur on the power
system that require an immediate
response to address deteriorating
conditions.
• IESO will make every attempt to
address the situation within the
confines of the DSO solution.
• Due to the nature of some events and
operational needs, IESO will resolve
the problem with the most efficient
control actions outside of the DSO
solution.
• IESO may communicate a mandatory
verbal dispatch instruction to the
variable generator to manage
reliability of the system.
19

Dispatch Mechanics: Summary
• DACP and pre-dispatch scheduling will respect hourly
forecast quantities as a constraint on how a variable
generator may be dispatched. Variable generators will be
scheduled in the same way as other dispatchable
generators
• MIO scheduling will respect 5-minute forecast quantities as
a constraint on how a variable generator may be
dispatched.
• In the absence of an economic or security constraint, realtime
dispatch targets (not sent to variable generators) will
be based on 5-minute forecasts and MIO advisories will use
5-minute forecasts for future intervals 20

Dispatch Mechanics: Summary
(cont’d)
• If an economic or security constraint exists on
the system, the variable generator may be
required to change its output and a dispatch
instruction will be sent with a Mandatory
Obligation Indicator
• In the first interval following a mandatory
dispatch instruction where the constraint no
longer exists and the generator can ramp to its
full output, a release notification will be sent to
the variable generator. 21

Compliance Deadbands

Definition and Rationale
• A compliance deadband allows a range of operations
that are considered compliant (see the current
interpretation bulletin on the Compliance pages of our
website).
http://www.ieso.ca/imoweb/pubs/interpretBulletins/ib_IMO_MKRI_0001.pdf
• The compliance deadband is intended for situations
where an attempt was made to meet the dispatch
instruction, but the facility fell short of or exceeded the
target.
23

Compliance Deadbands
• The current IESO compliance deadbands will be extended to
variable generators.
– For facilities >30 MW, deadband is greater of ± 15 MW or ± 2% of the
dispatch instruction
– For facilities < 30 MW, deadband is ± 10 MW from the dispatch
instruction
• Compliance to dispatch instructions will only be enforced when
Obligation Indicator is Mandatory and sufficient fuel exists.
• The market participant must notify the IESO if they cannot operate
within the compliance deadband during a mandatory dispatch due
to:
– Safety concerns;
– Damage to equipment; or
– Violation of any applicable law
24

Market Schedules

Market Schedule
• Use the telemetry snapshot at the end of the
interval if a dispatch instruction was not issued
for the interval or if a release notification was
issued
• Use the 5-minute forecast as an input to the
market schedule calculation for the interval if a
dispatch instruction was issued for the interval
26

Congestion Management
Settlement Credits (CMSC)

Congestion Management
Settlement Credits (CMSC)
• The outcome of the CMSC calculation will be the
same as for other dispatchable generators. To
achieve this, the CMSC calculation for variable
generators will be:
– Enabled in every interval subject to a mandatory
dispatch instruction
– Disabled for the dispatch intervals that are not subject
to mandatory dispatch instructions, including
intervals for which a release notification was issued.
28

As for other dispatchable generators:
CMSC (cont’d)
• If a generator’s offer price is below the lesser of $0 or
Market Clearing Price (MCP), the offer price is
adjusted to that lower limit.
‐ Example: Generator offers -$10/MWh, MCP is $25/MWh,
offer price adjusted to $0
• The CMSC equals zero for intervals in which the
mathematical sign of the [Constrained Schedule –
Market Schedule] is not equal to the mathematical
sign of the [Actual output – Market Schedule]
‐ Example: Mandatory dispatch to 75 MW, market schedule of
80 MW, actual output of 85 MW
29

100 MW variable generator :
CMSC (cont’d)
• No dispatch instructions for intervals ending 0:05, 0:10 and 0:35 – No CMSC
calculation performed
• Dispatch instruction for intervals ending 0:15, 0:20 and 0:25 – CMSC is
calculated
• Release notification for interval ending 0:30, generator can ramp to full in one
interval – No CMSC calculation performed
30

Tie-Breaking

Tie-Breaking
• Set all variable generator loss penalty factors to
1.0.
• The IESO will randomly generate a daily
dispatch order for a 3 month horizon:
– This 3 month dispatch order will be updated every
network model build (typically monthly) and new
months will be appended to the existing list
– As new generators connect, they will be at the bottom
of the order until a new month is published
– The randomly generated dispatch order will be
published on the IESO website.
– The new daily order will take effect for HE16 32

Forecast Reports

Forecast Reports
• Variable generators will have access to the
forecasts for their facilities
• Hourly forecasts will be made available
confidentially in advance of the dispatch hour
and show the entire 48-hour horizon
• Facility-specific forecasts will be made available
publically following the dispatch hour
• 5-minute forecasts will be available for the
previous hour as soon as possible following the
hour
• Reports will be available on the IESO website
34

DTWG Design
Summary Document

DTWG Design Summary Document
• The design decisions made through DTWG will
be compiled into a formal design document
• Design document will be presented to SE-91 as a
detailed summary of the design of dispatch
mechanics for variable generators
• This document will form the basis for market
manual development
• DTWG members will be given an opportunity to
read and provide comment on the document
before it is sent to SE-91
• Expected delivery to DTWG in early October 36