MISO has prepared a filing outline for stakeholder evaluation on its plan to bring distributed energy resource aggregations into its markets.
The RTO plans to lean on its existing dispatchable intermittent resource and electric storage resource participation models for FERC compliance. It would limit full dispatch participation to DER aggregations of 1 MW or greater, forcing those smaller than 1 MW to self-commit in the markets in order to participate. The RTO in early spring said necessary software changes would be too overwhelming if it fully accommodates the 0.1-MW minimum aggregation size outlined in FERC’s Order 2222. (See MISO to Recycle Participation Models for Order 2222.)
MISO will also limit a DER aggregation to a single elemental pricing node in its markets. (See MISO Wants Single Pricing Point for DER Aggregations.)
The RTO has until April 18, 2022, to submit a compliance filing to FERC. It has DER Task Force meetings and workshops with distribution companies scheduled nearly every month until the filing date.
“Research studies show broad, multi-node aggregations can lead to reliability concerns and power/price oscillations that are worsened with inaccurate distribution factors,” MISO said.
As an added bonus, MISO won’t have to make market clearing changes to accommodate the single-node dispatch of a DER aggregation, DER Program Director Kristin Swenson said at a special workshop June 7.
The RTO said it would not impose a maximum size limit on individual resources within an aggregation. But Swenson said MISO might glean through experience a maximum size threshold.
“We know we need automated data,” Swenson said, adding that individual phone calls to supply data from distribution companies to the MISO control room is an unrealistic option.
Swenson also said MISO still must figure out when a DER interconnection will require an affected-system study. She said unlike the affected-system studies between RTO territories, MISO in this case will be considered the affected system by the distribution system.
The decision to limit aggregations to a single pricing node will give MISO an easier time modeling the aggregations, Manager of Planning Modeling Amanda Schiro said.
“These decisions build upon one another,” she told stakeholders.
MISO plans to model an aggregation as a representative aggregate generator with positive or negative capabilities. The generator designation will minimally disturb MISO’s existing reliability and planning modeling, Schiro said.
Staff acknowledged that MISO’s modeling isn’t a swift process that can easily include mobile DERs or additions and deletions in aggregations.
“We do have this question about how do you update what’s in an aggregation,” Director of Settlements Laura Rauch said.
Swenson added that electric vehicle technology is at least a few years away from being true mobile resources.
While it’s up to regulatory authorities whether to allow dual participation in the retail and wholesale markets, MISO will probably devise a matrix provided to aggregations upon registration and enrollment in the RTO that shows which options for wholesale participation are compatible alongside retail market participation and which aren’t.
Swenson said MISO can use its existing market participation agreement with some modifications for aggregations, but the agreement does not negate the need for further operational agreements between DERs and aggregators.
MISO is taking stakeholder comments and suggestions on its filing approach through June 28.
