Impact of high renewable energy penetration on ERCOT’s frequency response reliability

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Kishek, Kameel Jiries Kamel

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The increased integration of renewable energy into the power grid can affect grid reliability during disturbances; frequency response time is affected by the generation and storage technologies active at the time. As less grid power comes from generators with synchronized rotating machines (e.g., coal, natural gas, nuclear), possibly due to increasing use of renewable energy, the system inertia decreases, making it harder to maintain grid frequency and stability. Fast Frequency Response (FFR) provides rapid power adjustment to stabilize frequency disturbances and maintain stability, and is associated with inverter-based resources, such as renewable and battery storage due to their ability to provide faster response relative to Primary Frequency Response (PFR) from conventional synchronous generators. The Electric Reliability Council of Texas (ERCOT) has witnessed high wind and solar penetration in the power grid, and consequently, a trend of lower system inertia. ERCOT has set rules and standards for generators providing FFR concurrent with the state of the grid. Using a single-generator model based on ERCOT’s PFR and FFR parameters and requirements, and 8 years of hourly historical system and day-ahead market prices data, this paper explores historical system frequency behavior during power loss events as compared to a situation when the grid is projected to be operating at ERCOT’s critical system inertia (100 GW-sec) and with FFR contribution. The economic effect on ERCOT market prices using coefficients that would reduce energy prices if FFR participation in frequency response offsets reserve capacity from thermal generators. Potential energy prices reduction for this offset capacity, when compared to the size of the market, was not significant. Therefore, it was deemed that regulatory orders may be more impactful on FFR adoption and deployment than potential reduction of market prices. This work emerges as ERCOT deliberates on the FFR Advancement Project, which incorporates FFR into the Ancillary Services (AS) market and offers additional insights into the future implementation and participation of FFR.


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