Virtual Meeting to Discuss a Report Issued Regarding Multiple Solar PV Disturbances in CAISO

Summary:

NERC and WECC recently published a report "Multiple Solar PV Disturbances in CAISO Disturbances between June and August 2021." The report is a Joint NERC and WECC Staff Report regarding four disturbances that occurred in Southern California involving the widespread reduction of power from solar photovoltaic (PV) resources connected to the bulk power system (BPS), specifically in areas with high penetrations of solar PV and wind resources. A virtual meeting will be conducted on May 10, 2022, from 1:00 to 3:00 p.m. (Eastern). This informational virtual meeting will answer industry questions about the report’s findings.

Additional Discussion:

Recommendations for Industry Action

• Reinforcement of Recommendations from the Odessa Disturbance Report: The NERC Odessa Disturbance Report outlined a number of strong recommendations to address known reliability gaps or issues for reliable operation of BPS-connected inverter-based resources (mainly solar PV resources). NERC reiterates the need for industry action on those recommendations. The NERC IRPS developed a follow-up white paper to the Odessa Disturbance Report that was approved by the NERC Reliability and Security Technical Committee (RSTC) and led to the IRPS adding multiple items to its work plan. NERC commends the RSTC and IRPS in being proactive to address identified reliability issues. NERC recommends the RSTC support the development of standards revisions (and future guideline development) to mitigate these reliability issues moving forward.

• Reinforcing that Significant Updates and Improvements are Needed to the FERC Generator Interconnection Agreements: All the performance issues identified in the NERC disturbance reports stem from a lack of performance requirements. These four events illustrate how the majority of affected facilities had minimal interconnection requirements applied to them and therefore introduced adverse impacts to the BES in aggregate. NERC guidelines highlight that TOs should establish detailed performance requirements, but those recommendations are not necessarily being comprehensively implemented. NERC recommends that the Federal Energy Regulatory Commission (FERC) update the pro forma interconnection agreements with all the necessary performance specifications covered in the NERC reliability guidelines to ensure that all resources are consistently and effectively being interconnected to the BPS. This will help ensure there are no gaps in performance for newly interconnecting resources. These updates should also be accompanied by clear requirements for accurate modeling and sufficiently detailed studies during time of interconnection, including electromagnetic transient (EMT) studies where necessary (most cases to ensure appropriate ride-through for BPS fault events). Finally, plant commissioning should involve validation that the models used during the system impact studies reflect the equipment being commissioned; inconsistencies that affect the electrical output of the facility should require additional studies prior to commercial operation to ensure BPS reliability and stability.

• Reinforcing that Improvements to NERC Reliability Standards are Needed to Address Systemic Issues with Inverter-Based Resources: This disturbance report strongly reiterates the recommendations in the Odessa Disturbance Report regarding the need to modernize and update the NERC Reliability Standards.  At a high level, these include the following:
  • Performance-Based Requirements: A number of NERC Reliability Standards require documentation that demonstrates compliance with the requirement (i.e., PRC-024-3); however, they do not specify a certain degree of performance that must be met. Therefore, any enforcement and auditing of these standards becomes poorly-defined and ineffective. This has led to unreliable operation of a large and growing number of solar PV facilities.
  • A comprehensive review of NERC standards should be performed to identify any standards where the requirements do not align with the desired intent of the standard from a performance-based perspective.
  • Future NERC Reliability Standard drafting teams should ensure that new or modified requirements are written in a manner to ensure an adequate level of reliable operation of the BPS while minimizing the documentation burdens to demonstrate compliance (i.e., focus on the performance-based aspects of the standard).

• Performance Validation Standard Needed: NERC strongly recommends that a performance validation standard be developed that ensures that Reliability Coordinators (RCs), TOPs, or Balancing Authorities (BAs) are assessing the performance of interconnected facilities during grid disturbances, identifying any abnormalities, and executing corrective actions with affected facility owners to eliminate these issues. This requires entities to have strong interconnection requirements as NERC highlights in its reliability guidelines and disturbance reports. A lack of performance validation (validating that the facility is performing as expected) has led to large-scale and widespread disturbances with many affected facilities rather than addressing underlying systemic issues before they become larger events. RCs, TOPs, and BAs should be performing performance assessments and validation for their generation fleet, identifying any unreliable operation of connected resources, and addressing those issues in a timely manner. The IRPS has a work plan item to develop a standard authorization request (SAR) on this topic.

• Ride-Through Standard In Lieu Of PRC-024-3: NERC strongly recommends that PRC-024 be retired and replaced with a comprehensive ride-through standard focused specifically on the generator protections and controls (not the auxiliary systems). PRC-024 is not effectively addressing systemic performance issues with inverter-based resources, and this has led to misinterpretations that have resulted in poor performance from solar PV facilities. Many entities now have ride-through requirements in their local interconnection requirements, and a NERC Reliability Standard will help ensure that the growing number of BES inverter-based resources are supporting overall BES reliability during disturbances moving forward. The IRPS has a work plan item to develop a SAR on this topic.

• Electromagnetic Transient Modeling and Model Quality Checks: NERC strongly recommends that EMT modeling and studies be incorporated into NERC Reliability Standards to ensure that adequate reliability studies are conducted to ensure reliable operation of the BPS moving forward. Existing positive sequence simulation platforms have limitations in their ability to identify possible performance issues, many of which can be identified using EMT modeling and studies. As the penetration of inverter-based resources continues to grow across North America, the need for EMT modeling and studies will only grow exponentially. Furthermore, NERC Reliability Standards need enhancements to ensure that model accuracy and model quality checks are explicitly defined. While models have been provided by applicable entities in most cases, NERC has identified numerous and systemic modeling issues and believes these issues are due to a lack of model quality reviews that are taking place during model submittals. The IRPS has a work plan item to develop a SAR on this topic.

• Other Reliability Standard Enhancements:  A number of additional recommended enhancements to NERC Reliability Standards that are reiterations of the Odessa Disturbance Report were also made.

Virtual Meeting Registration Link

https://nerc.webex.com/mw3300/mywebex/default.do?nomenu=true&siteurl=nerc&service=6&rnd=...