Integration Options into ERCOT
systems
Sai Moorty
ERCOT
Photovoltaic Resource
CIM Model (Network Model Management System-NMMS)
– Similar to current Generation Resource
• Single point of injection into grid
• Single Settlement Point
• High and low limits
– There are other attributes (or lack of) that need more discussions
when it comes to modeling:
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New Resource Type
No Synchronous machine with inertia
Invertor modeling
Reactive capability curve different
Short circuit parameters
Other?
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Photovoltaic Resource
Energy Management System (EMS)
Applications like State Estimation, Power Flow, Contingency Analysis
will have no change or minimal change. Currently identified EMS
applications that need to be modified or new are:
– MODIFICATION: Ancillary Service Capacity Monitor
• There may be a need to modify this application to take into account
intermittent nature of solar due to cloud cover etc. Note: currently
Wind Resources have resorted to not carrying Ancillary Service
Responsibilities.
– MODIFICATION: Online Transient/Voltage Stability Analysis
• There may be a need to change this application if current
capabilities cannot model Photovoltaic Resource correctly
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Photovoltaic Resource
Energy Management System (EMS)
– NEW: Solar potential forecasting application
• Short Term : 5 minute granularity for a rolling window looking out for
the next 2 hours
• Mid Term : 1 hour granularity for a rolling window looking out for the
next 2-7 days.
• Input to Solar potential forecasting application (every 30 seconds
via telemetry or other process?):
– Cloud cover monitor
– Solar farm latitude, longitude, alignment of solar panels, and
placement angle off horizontal
– Air temperature, Back of panel temperature
– Wind speed, Wind direction
– Global horizontal Irradiance
– For concentrated PV installations, in addition to the above,
direct normal Irradiance shall be telemetered
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Photovoltaic Resource
Market Management System (MMS)
The products that are available are Energy (MWHr) and Ancillary
Service Capacity (MW).
• Energy (MWHr) is procured in the Day-Ahead Market (DAM) in
terms of MW on a hourly granularity
• Energy (MWHr) is procured in the Real-Time Maket (SCED) in terms
of MW every 5 minutes and is settled on a 15-minute basis
• Ancilary Service Capacity (Regulation Up, Regulation Down,
Responsive Reserve, Non-Spin) is procured in terms of MW on a
hourly granularity in the Day-Ahead Market, Supplementary
Ancillary Service Market in the adjustment period and Resources
can assume AS responsibility via bilateral trades
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Photovoltaic Resource
Market Management System (MMS)
As far as the Day-Ahead Market and Real-Time Markets, our
current understanding is that Photovoltaic Resources will not
require any modifications to the Market Systems.
Expectations is that Photovoltaic Resources will be very similar to
Wind Resources as far as the Market Systems (including
Reliability Unit Commitment) are concerned.
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Energy Storage Resource
Salient Features of a Energy Storage resource
• Do not generate electrical energy like power plants (burning
fuel or converting external energy source like wind)
– Electrical energy is produced by time-shifting i.e. electrical
energy withdrawn from the grid over a particular time period and
stored (in some form) and subsequently injected back into the
grid at another later period of time
• Electrical energy consumed is not like loads
– Electrical energy not used for producing products or heating or
cooling or lighting. Electrical energy is stored for later release
back into the grid.
• Bi-directional, i.e. they can produce or consume electrical
energy
• Electrical energy can be stored for some period of time
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Energy Storage Resource
Salient Features of a Energy Storage resource (continued)
• Typically, are fast in responding to control signals
– Discharge and charging rates are high.
• Typically, Reactive capability in all four quadrants
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Energy Storage Resource – Modeling parameters
Parameter
Physical Unit Description
Generation
Resource
Equivalent
Max Storage Capacity
MWHr
Max nameplate energy storage
capability
n/a
Max Storage Level
MWHr
Max operating energy storage
capability
n/a
Min Storage Capacity
MWHr
Min nameplate energy storage
capability
n/a
Min Storage Level
MWHr
Min operating energy storage
capability
n/a
Storing Energy Efficiency
%
n/a
Max MW Discharging
Power
Min MW Discharging
Power
MW
Once fully charged, the
Percentage of energy compared
to max storage level, needed to
remain charged at max storage
level
Max operating MW discharging
power
Min operating MW discharging
power
MW
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HSL
LSL
Energy Storage Resource – Modeling parameters
Parameter
Physical Unit Description
Generation
Resource
Equivalent
Discharging Ramp Rate
MW/min
Rate for discharging in MW/min
Up Ramp Rate
Min Duration of
discharge
min
Min time to fully discharge from
Max Storage Level
n/a
Discharging efficiency
%
Percentage of energy losses
during discharge
n/a
Max operating MW charging
power
Min operating MW charging
power
MPC
Max MW Charging Power MW
Min MW Charging Power
MW
Charging Ramp Rate
MW/min
Rate for charging in MW/min
Down Ramp Rate
Min Duration of charge
min
Min time to fully charge from Min
Storage Level
n/a
Charging efficiency
%
Percentage of energy losses
during charge
n/a
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LPC
Energy Storage Resource – Modeling parameters
Parameter
Physical Unit Description
Generation
Resource
Equivalent
Min Time in Charging
Mode
Min Time in Discharging
Mode
Min Time in Offline Mode
min
Min Up Time
Max Number of Off-ToCharging Transitions
Max Number of Off-ToDischarging Transitions
Time to transition from
charging to discharging
Time to transition from
discharging to charging
TBD
min
min
Minimum time to be in charging
mode
Minimum time to be in
discharging mode
Minimum time to be in offline
mode
Maximal number of charging
cycles in a day
Maximal number of discharging
cycles in a day
min
Min Up Time
Min Down Time
Max Number of Starts
Max Number of Starts
n/a
min
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Energy Storage Resource
CIM Model (Network Model Management System-NMMS)
– Detailed discussions with Resource Entities, QSEs are required
to get a common understanding of the modeling requirements
– Modeling of Storage Resources can also include aggregation of
small storage resources (similar to Aggregated Load Resources)
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Energy Storage Resource
Energy Management System (EMS)
Applications like State Estimation, Power Flow, Contingency Analysis
will have no change or minimal change. Currently identified EMS
applications that need to be modified or new are:
– MODIFICATION: Ancillary Service Capacity Monitor
• There may be a need to modify this application to take into account
the energy storage level.
– MODIFICATION: Online Transient/Voltage Stability Analysis
– There may be a need to change this application if current
capabilities cannot model Energy Storage Resource correctly
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Energy Storage Resource
Energy Management System (EMS)
– NEW: Telemetered quantities – for example
• Stored Energy Level
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Energy Storage Resource
Market Management System (MMS)
The products that are available are Energy (MWHr) and Ancillary
Service Capacity (MW).
• Energy (MWHr) is procured in the Day-Ahead Market (DAM) in
terms of MW on a hourly granularity
• Energy (MWHr) is procured in the Real-Time Maket (SCED) in terms
of MW every 5 minutes and is settled on a 15-minute basis
• Ancilary Service Capacity (Regulation Up, Regulation Down,
Responsive Reserve, Non-Spin) is procured in terms of MW on a
hourly granularity in the Day-Ahead Market, Supplementary
Ancillary Service Market in the adjustment period and Resources
can assume AS responsibility via bilateral trades
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Energy Storage Resource
Market Management System (MMS)
Due to the limited energy available from Energy Storage
Resources, care will have to be taken as to which products are
most suitable. There are compliance penalties if Resources do not
perform to their obligations
Currently there is a pilot project in the works “ Fast Responding
Regulation Service” to evaluate the performance of Resources
capable of extremely fast regulation service. Storage Resources
like Batteries can participate.
Introduction of any new technology neutral product will need to be
vetted through the stakeholder process
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Summary
ERCOT System
Photovoltaic
Energy Storage
Comment
Registration (RARF)
Small-Medium
Large
Dependent on modeling
NMMS
Medium
Large
EMS
Medium
Large
MMS
Small
Large
S&B
?
?
Schema changes will
need to be scalable to
anticipated other new
types of Resources
Additional telemetry and
new applications
Photovoltaic similar to
Wind from MMW
perspective
Energy Storage will
require significant
changes
Depends on outcome of
stakeholder process
TBD
?
?
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