IDEAS: Issue #1: DER Definition
 Issue Identified:
What is the ERCOT definition of DER? Answering this question is necessary to
determine the lexicon for Section 2 of the Nodal Protocols with respect to Distributed
Energy Resources, and it is also necessary as a foundation for framing clear and precise
discussion and consideration of this subject.
 Issue Development:
The current definitions for Resource types as described in Section 2 of the ERCOT Nodal
Protocols are deemed not sufficient to describe the “DER” resource type, due to the
potential market entry by Resource Entities that are representing, or intend to
represent, assets connected on the distribution system at 60 kV or below that may
consist of generation and/or storage, or an aggregation of generation and/or storage,
or an aggregation of generation and/or storage and/or load resource, but never a load
resource by itself, and that are capable of injecting electrical energy onto the
distribution system.
Further, given that there may be different levels of market engagement by a DER, to
include nodal vs load-zone settlement, or self-responding vs SCED-dispatched, it
becomes necessary to establish definitions for the sub-types of DER.
In the ERCOT Concept Paper on Distributed Energy Resources in the ERCOT Region
Submitted to the Distributed Resource Energy & Ancillaries Market (DREAM) Task
Force on August 19, 2015, the draft definition for Distributed Energy Resources is,
“A generation or energy storage technology, or combination of generation
and/or energy storage technologies, that is interconnected at or below 60 kV,
operates in parallel with the distribution system, and is capable of injecting
electrical energy onto the distribution system.”i
This issue and this draft definition are framed by the existing regulatory framework,
which includes the following:
Substantive Rule §25.501(h) says that,
“ERCOT shall use zonal energy prices for loads […]”.ii
ERCOT Nodal Protocols Section 2.1 define Load Resource as,
“A Load capable of providing Ancillary Service to the ERCOT System
and/or energy in the form of Demand response and registered with
ERCOT as a Load Resource.”iii
One of the sub-sets of Load Resources, Aggregate Load Resource, is
defined within the ERCOT Nodal Protocols Section 2.1 as,
“A Load Resource that is an aggregation of individual metered
sites, each of which has less than ten MW of Demand response
capability and all of which are located within a single Load
Zone.”iv
ERCOT Nodal Protocols Section 2.1 define Generation Resource as, “A
generator capable of providing energy or Ancillary Service to the ERCOT
System and is registered with ERCOT as a Generation Resource. The term
“Generation Resource” used by itself in these Protocols does not include a
Non-Modeled Generator.”v
One of the sub-sets of Generation Resources, Aggregate Generation
Resource, is defined within the ERCOT Nodal Protocols Section 2.1 as,
“A Generation Resource that is an aggregation of non-wind
generators, each of which is less than 10 MW in output, which
share identical operational characteristics and are
interconnected at the same POI and located behind the same
Generator Step-Up (GSU) transformer (with a high-side voltage
greater than 60 kV).”vi
Neither existing Load Resource or Generation Resource definitions, nor the draft DER
definition, allow for the full variety of asset arrangement and market engagement
schema described by industry representatives, and so does not give these resources
open access to the market.
Given that a DER may at times act as a Generation Resource, may at other times be
inclusive of a Load Resource, and at other times may be more like a Non-Modeled
Generator, it may then be reasonable to also think of DERs in the context of an AllInclusive Resource.
All-Inclusive Resource is defined within the ERCOT Nodal Protocols Section 2.1
as,
“A term used to refer to a Generation Resource, Load Resource and a
Non-Modeled Generator.”vii
Also, a Non-Modeled Generator is defined within the ERCOT Nodal Protocols
Section 2.1 as,
“A generator that is:
(a) Capable of providing net output of energy to the ERCOT System;
(b) Ten MW or less in size; or greater than ten MW and registered with
the PUCT according to P.U.C. Subst. R. 25.109, Registration of Power
Generation Companies and Self-Generators, as a self-generator; and
(c) Registered with ERCOT as a Non-Modeled Generator, which means
that the generator may not participate in the Ancillary Service or
energy markets, RUC, or SCED.”viii
 Detailed Explanation:
This definition takes the basic concept that a DER is a single generation resource or an
aggregation of various generation/storage and load resources that is a net injection
onto the system.
 Analysis:
How is storage (including EVs) treated in definition? Storage is treated as a generation
resource in this definition. However, EVs are a little different if they are only used to
stop charging and not discharging to the system, the latter of which most EVs are not
currently capable. If only stop charging then that would be considered DR.
How does Wholesale Storage Load treatment factor into the DER issue? It only factors
into the COP status or settlement of the overall resource.
 Solve/Solution:
Given the issues and analyses above, the following definition for Distributed Energy
Resource is proposed:
Distributed Energy Resource
An individual generator or storage device, or an aggregation of any
combination of generators, storage devices, or Load Resources, interconnected
at or below 60 kV, interconnected in the same Load Zone, and capable of
injecting electrical energy onto the distribution system.
DER-Minimal
[to be discussed further in Task Force meetings] Status Quosimilar to current DG treatment; self-responding; settled at
Load Zone.
DER-Light
[to be discussed further in Task Force meetings] A DER that is
self-responding and has a finer locational settlement than Load
Zone.
DER-Heavy
[to be discussed further in Task Force meetings] A DER that is
SCED-dispatched and has locational settlement, approximately
commensurate in grid topology detail with modeled
Generation Resources, but which may not include a Load
Resource as part of the DER.
DER-Heavy(Z)
[to be discussed further in Task Force meetings] A DER that is
SCED-dispatched and that is settled at the Load Zone.
This definition addresses what is a DER. The above definition takes the high-level
stance that it does not matter what is in the aggregation. Rather, what matters is
whether, or not, the Resource is a capable of a net injection to the system.
ERCOT Concept Paper on Distributed Energy Resources in the ERCOT Region
Submitted to the Distributed Resource Energy & Ancillaries Market (DREAM) Task
Force on August 19, 2015. [Version 1.0]
i
ii
CHAPTER 25. SUBSTANTIVE RULES APPLICABLE TO ELECTRIC
SERVICE
PROVIDERS.
Subchapter S. WHOLESALE MARKETS.
§25.501. Wholesale Market Design for the Electric Reliability Council of Texas.
(h) Zonal energy prices for loads. ERCOT shall use zonal energy prices for loads that
consist of an aggregation of either the individual load node energy prices within each
zone or the individual resource node energy prices within each zone. Individual load
node or resource node energy prices shall be the locational marginal prices, consistent
with subsection (e) of this section, resulting from security-constrained, economic
dispatch. ERCOT shall maintain stable zones and shall notify market participants in
advance of zonal boundary changes in order that the market participants will have
an appropriate amount of time to adjust to the changes.
ERCOT Nodal Protocols 2.1
ERCOT Nodal Protocols 2.1
v ERCOT Nodal Protocols 2.1
vi ERCOT Nodal Protocols 2.1
vii ERCOT Nodal Protocols 2.1
viii ERCOT Nodal Protocols 2.1
iii
iv