ISO-NE is working to add to its probabilistic energy adequacy tool the capability to model preemptive actions to help conserve stored fuel prior to extreme winter weather events, ISO-NE representatives told the NEPOOL Reliability Committee (RC) on Oct. 22.
The probabilistic modeling framework, or PEAT, initially was developed in coordination with the Electric Power Research Institute for several long-duration shortfall risk evaluations in 2023. It now is being incorporated into ISO-NE’s energy assessments and would be the backbone of the RTO’s proposed Regional Energy Shortfall Threshold (REST).
REST is intended to quantify and determine an acceptable level of shortfall risk for the region, and eventually to inform the development of solutions when risks are identified. (See ISO-NE Details Proposal for Regional Energy Shortfall Threshold and NEPOOL Reliability/Transmission Committee Briefs: Aug. 13-14, 2024.)
ISO-NE plans to run REST analyses seasonally to evaluate near-term shortfall risks and over longer periods to better understand risk trends in the region.
The PEAT modeling is being improved to account for both preventive and corrective capacity deficiency actions, said Mike Knowland of ISO-NE. While the PEAT modeling already includes corrective actions, modeling preventive actions is a new addition.
“Incorporating both preventive and corrective actions directly into PEAT allows for a robust quantitative estimate of the impacts of these actions on shortfall amounts,” Knowland said, adding that the modeling will be able to isolate the effect of preemptive actions.
The preemptive modeling is intended to help the RTO optimally dispatch resources prior to and during extended periods of resource adequacy risk, which ISO-NE expects to increase as intermittent renewables proliferate.
Jinye Zhao of ISO-NE said the RTO also “has significantly enhanced PEAT to incorporate a multiday rolling-horizon economic dispatch for the 21-day energy assessment,” which looks out three days in advance on a rolling basis to optimize the dispatch of stored fuel resources.
“Based on system conditions and fuel availability in the future days, the model can decide the appropriate time to trigger preventive actions and allocate the appropriate amount as needed to alleviate an anticipated energy shortfall,” Zhao said.
In the new process, ISO-NE first will conduct its 21-day energy assessment using only modeling of corrective shortfall actions. Following the identification of an energy shortfall, the RTO will run the assessment again and include modeling of both preventive and corrective actions.
Net import relief and net conservation relief, which will be incorporated in both the preemptive and corrective PEAT modeling, each will be “modeled as a block of up to 500 MW,” Zhao said.
For the REST project, the modeling improvements could enable “a multimetric criteria which may include an additional metric that captures the duration of energy shortfall,” the RTO told stakeholders.
ISO-NE is scheduled to present its initial proposal on the REST at the RC in November. It has emphasized the need for stakeholder input on the level of acceptable shortfall risk for the region.
Determining an acceptable risk threshold will require more than just modeling expertise — it will pose political questions about how much the states are willing to pay for reliability insurance on the grid, and it could have a significant impact on regional programs supporting stored-fuel or dispatchable resources.
“Following establishment of the REST, a subsequent effort will evaluate if adherence to the REST requires development of specific regional solutions,” Knowland noted.
ISO-NE’s inventoried energy program (IEP), which compensates generators for keeping stored fuel on site during the winter, is set to expire after this winter. While the IEP was intended as a short-term solution, the RTO has not committed to either ending or continuing the program.
Presenting the results of the RTO’s Economic Planning for the Clean Energy Transition report at the Planning Advisory Committee meeting in August, Patrick Boughan of ISO-NE emphasized that new market enhancements may be needed in the long-term to support dispatchable resources as renewables proliferate. (See ISO-NE: New Mechanisms May be Needed to Ensure Future Grid Reliability.)
