ERCOT Says RTM, DAM Prices Under Investigation For Potential Correction Due To MMS Error

ERCOT issued a market notice stating that real-time and day-ahead prices, dating back to approximately February 8, 2023 (specific date market-dependent as noted below), "are under investigation for potential correction due to an error identified in ERCOT's Market Management System (MMS) impacting Load Zone Calculations in the Real-Time Market (RTM) and Day-Ahead Market (DAM)."

"ERCOT has identified an error in the ERCOT MMS that impacted Load Zone calculations for both the RTM and DAM," ERCOT said in the notice

"ERCOT Protocols Sections 6.6.1.2 and 6.6.1.4 require that, for the RTM, the calculation of Load Zone prices exclude the charging loads associated with Energy Storage Resources (ESRs). Contrary to ERCOT Protocols Sections 6.6.1.2 and 6.6.1.4, an error identified by ERCOT resulted in the ERCOT MMS including the loads associated with ESRs, when the ESRs were charging, in the calculation of Real-Time Load Zone prices. In the RTM, this error likely impacted the calculations of Real-Time Load Zone Locational Marginal Prices (LMPs) and Real-Time Settlement Point Prices (RTSPPs) for certain Load Zones where ESRs are located," ERCOT said in the notice

"Due to the same error, the DAM was also impacted where loads associated with ESRs were incorrectly mapped to a Load Zone. As a result of this, the Load Distribution Factors for the loads associated with ESRs were included in the calculation of Day-Ahead Shift factors for certain Load Zones and likely impacted the DAM clearing," ERCOT said in the notice

"ERCOT has determined that the error was related to the method in which MMS determines if an Electrical Bus is associated with an ESR Load Resource. The MMS relies on a set of tables from the Network Model Management System (NMMS) to determine if an Electrical Bus is associated with an ESR Load Resource. Those associated Electrical Buses are then excluded from Load Zone Price calculations. However, this table dependency and a recent change to one of those NMMS tables resulted in the MMS incorrectly including those Electrical Buses in the Load Zone calculations. The potential price impacts started on February 8, 2023, when the changes to the applicable tables were first implemented. At this time, there are 72 loads associated with ESRs in the ERCOT system," ERCOT said in the notice

"ERCOT staff implemented a fix to the MMS on March 8, 2023, that resolved this issue. This took effect for the RTM for Operating Day March 8, 2023, and for the DAM for Operating Day March 9, 2023. For the RTM, this means that the Operating Days that were potentially impacted are February 8, 2023 through March 7, 2023. For the DAM, the range of Operating Days that were potentially impacted is February 9, 2023 through March 8, 2023," ERCOT said in the notice

"For any Operating Days meeting the criteria for significance for an ERCOT Board of Directors (Board) review of prices and for which ERCOT is able to determine accurate prices, ERCOT will seek a review of prices by the Board. The specific Board meeting will be dependent on the time necessary for the impacts and significance to be analyzed. ERCOT will provide a follow up Market Notice after the investigation is complete to identify any Operating Days for which ERCOT staff will seek Board review and the specific meeting at which that review will be sought. Information regarding the criteria for significance can be found in Protocol Sections 4.5.3(6)(b) and 6.3(7)(b), for the DAM and RTM, respectively," ERCOT said in the notice