PJM addresses DER aggregation at FERC conference 


PJM participated in four of the seven panels during the Federal Energy Regulatory Commission’s recent technical conference, with discussion focusing on the scope of FERC’s role in distributed energy resources.

The commission said the conference, held April 10 and 11 in Washington, D.C., will help it determine action to take on reforms proposed in its Notice of Proposed Rulemaking (NOPR) for distributed energy resources (DER) aggregation.

PJM defines DER differently than does the Notice of Proposed Rulemaking.  PJM considers DER to be any generation or electric storage resource connected to distribution or behind a customer’s meter. PJM also makes the distinction between wholesale DER and non-wholesale DER. Wholesale includes the voluntary participation of DER in PJM markets, and non-wholesale involves DER that offset retail load or are otherwise compensated under a retail tariff.

Regarding non-wholesale DER, PJM already forecasts solar in its long-term planning process to ensure that the impact on load is taken into account when PJM procures capacity through the capacity market and plans transmission upgrades.  Regarding wholesale DER, there are hundreds of megawatts today connected to distribution voltage and participating in PJM markets as wholesale generators.

Panel: Economic Dispatch, Pricing, and Settlement of DER Aggregations

The first panel’s focus was the integration of DER aggregations into the modeling, clearing, dispatch and settlement mechanisms of RTOs and ISOs.

FERC wanted to know which approaches are available to ensure that the dispatch of a multi-node DER aggregation does not exacerbate a transmission constraint. The commission did acknowledge that some RTOs/ISOs already allow aggregations across multiple pricing nodes.

Andrew Levitt, PJM senior market strategist, said that nodal precision was important and can be maintained with wide-area aggregation. Since granular control of a wide area would not be available, the ability to control congestion would be limited.  This concern can be mitigated with maximum size or geographic limits, among other solutions.

Even though transmission constraints might change over time, Levitt added, a wide-area DER aggregation that is modeled with nodal precision would not need to be revisited as system topology changes. This is due to the application of biddable distribution factors (that would restrict the dispatch of DER on the wrong side of constraint) together with restrictions on the maximum size of an aggregate. For context, Levitt compared the one megawatt maximum aggregation size cap currently proposed in the PJM DER stakeholder process to the error in real-time (50 MW) and settlement metering of a PJM tie line (10 MW).

Regarding special reliability considerations, Levitt said: “PJM cannot schedule or dispatch a subset of the aggregation. With a max size limit for a single resource, a grid operator could possibly implement an overall aggregation program size limit or rules to progressively shrink geographic area.”

The commission wondered about settlements for a multi-node DER aggregation. Levitt said that if the commission allows aggregations to participate in markets, DER aggregation located across multiple pricing nodes should be settled on a disaggregated, per-unit basis.

“This would be the same as weighted average with the weighting based on actual performance. Any other weighting would be wrong,” Levitt said.

From PJM’s independent market monitor, Monitoring Analytics, Joe Bowring also participated in this panel.