DREAM November Meeting

Agenda

• Introduction and Expectations• Path to becoming a Resource Node – ERCOT• Registration process for non-modeled resources – ERCOT• Distribution Switching 101• Reliability Discussion – DERs (December)• Modeling DERs at the Transmission Bus• FIS / Screening Study Exemption for DERs• Definition Update• Resource Optionality and Switching between LZ and Nodal

Prices

Expectations

• Understand and differentiate registration processes for resource nodes and un-registered resources

• Identify bottlenecks for establishing a resource node for a DER

• Understand complications associated with DER registration and distribution switching

• Document task force positions on LZ/Nodal switching

Distribution Switching 101

Feeder A Feeder B Feeder C

Main 1 Main 2

Feeder D Feeder F Feeder G

T BKR 1

Transmission Line 1

Transmission Line 2

Transformer 1138/13.8kV

Transformer 2138/13.8kV

Fault duty rated disconnect switch

Fault duty rated disconnect switch

T BKR 2

SubstationFence

Residential Service

Commercial, Light Industrial, Residential Service

DERville Substation

Field switching between feeders

Field switching between substations

ODER YODER

Modeling DERs at the transmission bus

DER

• Establishing a Logical Resource Node for a DER enables participation in SCED dispatch, ancillary service markets, and CRR markets.

• The resource’s electrical identity on the grid can be represented by an equivalent circuit, and shift factor relative to the transmission bus

• A DER with many parallel paths back to a substation still has a shift factor of 1, relative to the T/D transformer, assuming it is truly “radial” to that transformer

• Downtown networks with tied secondary lines are notable exceptions

Mapping a DER to the Transmission Load

• DERs can be modeled at the transmission bus

• Shift factors relative to constraints can accurately represent the resource at the transmission bus

• Switching between substations may physically move the resource connection relative to it’s DER mapping

• CIM nodes must be logically adjusted to account for DER output and apparent load.

Sub 1 Sub 2

DER1

CIM Load

Distribution switching is not currently modeled by ERCOT

Potential Solution for Distribution Switching impact on resource location

The ability to switch load (and distribution connected resources) is typically limited by physical and electrical distance in between transmission substations.

Sub 1

Sub 1

Sub 1

Sub 1

Sub 130 Mi 40 Mi 20 Mi

25 Mi

Load / DER

Load / DER Load / DER

Voltage and Thermal Constraints Limit D Switching

Resource switching may be limited to immediately neighboring circuits / stations

Potential Solution for Distribution Switching impact on resource location

If the resource can only switch between two substations that have a shift factor +/- 2% (shift factor cut-off), then the resource may be modeled at either substation without material impact. Station outages may require that a DER QSE notify ERCOT of the change for accurate representation.

Sub 1

Sub 1

Sub 1

Sub 1

Sub 130 Mi 40 Mi 20 Mi

25 Mi

Load / DER

Load / DER Load / DER

Voltage and Thermal Constraints Limit D Switching

Resource switching may be limited to immediately neighboring circuits / stations

Potential Exemptions for FIS Studes

• Do TDSP interconnection studies obviate the need for further ERCOT study?

• Does the 10MW Exemption allow a bypass of ERCOT/ FIS studies?

• If the DER Nameplate rating < Station Transformer minimum load, then the DER may not inject to the grid

Behind the meter, LZ Pricing

Battery Solar Panel

Inverter

Load

Meter

Load ZoneChargingPricing

Load Zone Pricing

Load Zone Pricing

Load Zone Pricing

Net apparent load invoiced by interval

Behind the meter, LZ/Nodal Pricing

Battery Solar Panel

Inverter

Load

Meter

NodalChargingPricing

Nodal / Solar Charging Pricing

Load Zone Pricing

Nodal Pricing

Logical load invoiced by interval

Sub Meter

Logical Load may be defined as Meter – Sub Meter

Load Zone/Nodal Optionality

• Wholesale and Load Zone prices may diverge when constraints bind

• Resources and Loads may get inconsistent pricing at the same electrical bus

This issue exists at traditional generators, where station service load pays load zone pricing and the generator is paid wholesale pricing

Electrically equivalent location

Nodal and Load Zone Price Divergence

• If a customer site is in a load pocket within a load zone, nodal prices may be very high, while load zone prices are relatively low.

• If a customer site is in a generation pocket within a load zone, LZ pricing may be very high, while nodal prices are very low

Issues with Optionality

• The ability to switch between nodal and load zone pricing, on an interval, hourly, or daily basis enables the customer to optimize charging, discharging, and LZ/Nodal Pricing

• Provides an unprecedented opportunity to manage load zone / nodal risk

Examples: Day (hour, week, month)1

Optimizing LZ/NP, the resource would:– Switch batteries to full

charging mode– Switch solar production

to self serve (Load Zone hedge)

– Potentially reduce Load

NP : -$25

Note: Assumes sub-metering on the battery and solar array are independent and switchable (Potentially Post-ITC Scenario, ITC for batteries requires 70% solar charging)

LZ: $30

Examples: Day (hour, week, month) 2

Optimizing LZ/NP, the resource would:– Switch batteries to full

dis-charging mode– Switch solar production

to nodal pricing– Potentially increase

charging load to discharge to a nodal price

NP : $30

Note: Assumes sub-metering on the battery and solar array are independent and switchable

LZ: $18

Pros/Cons

• Creates increased value for the solar/storage combination behind the meter

• Enables unprecedented optionality for a Resource to optimize LZ/Nodal pricing

• Potentially sends differing/conflicting pricing signals to a single electrical location

Alternatives

• Establish a Resource Node for the Solar/Battery combination

• Charge and Sell wholesale• Procure CRRs from the Resource Node to the

Load Zone when LZ pricing is desired

Next Meeting

• Discuss potential rules for aggregations• Review year-to-date findings• Prepare a summary for TAC direction in

January• DER Reliability Discussion – Current DR Concentration– Can existing DR aggregate output currently exceed

Reg Down, SCED Down on a 5, 10, 15 min basis?