Evelyn Hernandez from Nordex presented on the challenges and limitations of Inverter-Based Resources (IBRs) for winter turbines under low power production and frequency events.
Discussed the NERC standard for primary frequency response in ERCOT and its narrow deadband which leads to frequent excursions and potential challenges for wind turbines operating at or below technical minimums.
Explained the concept of technical minimum, the lowest power output at which a wind turbine can operate, typically about 10% of rated power for Nordex turbines.
Scenarios
Scenario 1: Challenges with curtailed operations responding to under-frequency events, where response time can take 1 to 5 minutes due to various turbine checks and physics.
Scenario 2: Challenges when curtailed below technical minimums, requiring turbines to be switched off and on, leading to potential delayed response.
Scenario 3: Low available power scenario where wind variability combines with frequency variability, causing frequent turbine switching.
Proposals
Introduce a dead time to reduce frequency event counts and minimize turbine switching.
Ensure frequency measurements align with ERCOT standards.
Update BAL-001-TRE-2 to acknowledge technology limitations and incorporate the technical minimum concept in the grid code.
Questions and Clarifications
Luis clarified on turbine technical minimums and curtailment control by Nordex's PPC.
Discussion on controller logic optimization to avoid unnecessary turbine shutdowns in frequency response scenarios.
Inquiry into differentiating responsibilities of controller manufacturers and turbine capabilities.
3 - Brainstorm for Potential Solutions on PFR under Deep Curtailment - All
The speaker introduced the basics of wind turbine generation from a system planner's perspective, emphasizing the differences between wind turbines and synchronous machines.
Key aspects of turbine operation such as variable speed, lift mechanics, and tip speed ratio were discussed. The necessity of maintaining a variable speed for maximum power production was explained.
Different models of generators, like double fed induction generators and full converter machines, were mentioned in relation to variable speed control.
The mechanical constraints of wind turbines, including inertia and pitch control, were outlined to highlight their impact on power generation and response to curtailment.
The complexities of controlling wind turbines, especially during deep curtailment scenarios, were examined. Different strategies to manage CP curves, turbine speed, and mechanical power input were presented.
Issues related to maintaining power production under different wind conditions were discussed. The discussion included the challenges of achieving deep curtailment and maintaining stability.
The speaker explained the concept of technical minimum and why turbines cannot be curtailed below a certain operational threshold without affecting stability.
The physical limitations and vibrations associated with turbine operation at low speeds were detailed, emphasizing the mechanical stresses involved.
The impact of wind turbine operation under low wind speed conditions was scrutinized, along with constraints such as mechanical pitch and rotor speed adjustments.
A discussion on how power plant controllers manage Primary Frequency Response at a plant level ensued, considering the varying operations and strategies among different turbines.
The complexity of turbine logic and its response to changes in power availability was highlighted through examples from past case studies.
4 - Review and Discussion of NOGRR272 and PGRR121 related to Advanced Grid Support Requirements for Inverter-Based ESRs - Fred Huang - ERCOT
ERCOT proposed new requirements through PGRR121 and NOGRR272 to adopt advanced grid support for energy storage resources (ESRs).
The system is expected to become weaker with more inverter-based resources (IBRs), prompting ERCOT's efforts for system strength and grid resiliency improvements.
AGS ESR adaptations are part of ERCOT's initiatives for enhancing grid stability and resiliency.
ERCOT has presented these proposals in multiple past workshops and posted related reports for stakeholder review.
NOGRR272 incorporates a new section 2.14 in the Nodal Operating Guide, requiring new ESRs with SGIA execution dates on or after April 1, 2025, to comply with performance requirements.
PGRR121 expands existing model quality test requirements to include AGS ESRs in the Planning Guide.
Stakeholder review of these documents began on October 31, with a first discussion scheduled for the December ROS meeting.
Queries regarding SGIA execution and amendment dates were raised, with ERCOT noting potential conditions regarding the GINR process.
The timeline for further discussion includes updates to DWG procedure manuals and plans to address and incorporate feedback in future meetings.
5 - SPWG / IBRWG Coordination on Multiple-Ride Through and Next Steps Discussion - Mark Mcchesney - Oncor, SPWG chair, All
Action Item from ROS: Develop recommendations for auto reclosing and sectionalizing schemes to improve IBR ride-through capability.
Key issues from IEEE 2800: number of voltage deviations required to be ridden through, phasing changes (25 electrical degrees).
Concerns about adjacent lines to IBR POI regarding reclosing into a fault, the number of recloses, and allowable phase angles.
Survey conducted: Limited responses (5 TDSPs), reclosing varied significantly in intervals and number of shots.
Need for strong dialogue between IBR plants and TDSPs to understand reclosing practices.
Discussion on potential inclusion of maximum phase angle jump and reclosing settings in dynamic interconnection studies.
Concerns that coordination between IBR plants and TDSPs might fall through the cracks without formal procedural documentation.
Transparency among TDSPs on reclosing philosophies during interconnection processes.
Consideration if phase angle jump should be included in interconnection studies.
Recommendations to engage ERCOT's Resource Integration Group to address interconnection coordination guidance.
6 - Other Industry Updates - Julia Matevosyan - ESIG
Updates on advanced grid-forming capabilities for ESRs, highlighting efforts similar to MISO's requirements for future batteries.
MISO's proposal to require grid-forming capabilities from all batteries starting with the 2023 study cycle, and is outlined in the Business Practice Manual.
Discussion about other system operators and their current grid-forming specifications, including HECO, NESO, AEMO, Fingrid, and ENTSO-E.
Mention of OEMs with commercial offerings of grid-forming capabilities.
Overview of interconnection requirements and standards for inverter based resources, emphasizing NERC and DOE's efforts.
NERC addressed milestone 2 of FERC Order 901
Details on FERC's actions and standards submitted, including modifications to PRC-024, PRC-002, and performance issue mitigation.
NERC issued a summary of milestone 3 and plans on holding a technical workshop on January 15-16th
There is work on IEEE P2800.2 and its guide for conformity assessment and ongoing workshops to enhance industry standards.
Summary of ESIG's Fall workshop sessions related to grid-forming technology, interconnection of large loads, reliability with high levels of IBR, and EMT practices and applications.
