GRADIENTS CP NOFO Mod 01.pdf

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AR-311-10.24

FINANCIAL ASSISTANCE

NOTICE OF FUNDING OPPORTUNITY

ADVANCED RESEARCH PROJECTS AGENCY – ENERGY (ARPA-E)

U.S. DEPARTMENT OF ENERGY

GRID RELIABILITY WITH AUTOMATIC DAMPING AND INERTIA

FOR ELECTRICAL NETWORKS AND TRANSMISSION SYSTEMS

(GRADIENTS)

Announcement Type: Initial Announcement Modification 01 Notice of Funding Opportunity No. DE-FOA-0003554

Assistance Listing Number 81.135

Mod. No. Date Description of Modifications

01 2/6/2025 • Clarified the meaning of the Program Policy Factors in Section V.C.

• All modifications to the Notice of Funding Opportunity (NOFO) are highlighted in yellow in the body of the NOFO.

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TABLE OF CONTENTS

BASIC INFORMATION ......................................................................................................................................... - 5 -

I. FUNDING OPPORTUNITY DESCRIPTION ..................................................................................................... - 7 -

A. AGENCY OVERVIEW ........................................................................................................................................... - 7 - B. PROGRAM OVERVIEW........................................................................................................................................ - 9 - C. PROGRAM OBJECTIVES ................................................................................................................................ - 14 - D. TECHNICAL CATEGORIES OF INTEREST ............................................................................................................. - 16 -

1. CATEGORY 1: FLEXIBLE RENEWABLE GENERATION .......................................................................................... - 16 -

2. CATEGORY 2: INTELLIGENT AUTOMATIC RELAYS ............................................................................................. - 17 -

3. CATEGORY 3: WIDE-AREA RT-CCD ............................................................................................................. - 18 -

E. TECHNICAL PERFORMANCE TARGETS .................................................................................................................. - 20 - F. TECHNOLOGY TO MARKET CONSIDERATIONS ....................................................................................................... - 28 - G. STATEMENT OF SUBSTANTIAL INVOLVEMENT ................................................................................................... - 28 - H. FUNDING RESTRICTIONS .............................................................................................................................. - 29 -

1. ALLOWABLE COSTS .................................................................................................................................... - 29 -

2. PRE-AWARD COSTS ................................................................................................................................... - 30 -

3. PATENT COSTS .......................................................................................................................................... - 30 -

4. CONSTRUCTION ......................................................................................................................................... - 30 -

5. FOREIGN TRAVEL ....................................................................................................................................... - 30 -

6. PERFORMANCE OF WORK IN THE UNITED STATES............................................................................................ - 30 -

7. PURCHASE OF NEW EQUIPMENT .................................................................................................................. - 31 -

8. TECHNOLOGY TRANSFER AND OUTREACH ...................................................................................................... - 31 -

9. LOBBYING ................................................................................................................................................ - 31 -

10. CONFERENCE SPENDING ............................................................................................................................. - 32 -

11. INDEPENDENT RESEARCH AND DEVELOPMENT COSTS....................................................................................... - 32 -

12. BUY AMERICA REQUIREMENT FOR PUBLIC INFRASTRUCTURE PROJECTS .............................................................. - 33 -

13. REQUIREMENT FOR FINANCIAL PERSONNEL .................................................................................................... - 33 -

14. PARTICIPANTS, COLLABORATING ORGANIZATIONS, AND CURRENT AND PENDING SUPPORT ................................... - 33 -

II. ELIGIBILITY INFORMATION ...................................................................................................................... - 35 -

A. ELIGIBLE APPLICANTS ....................................................................................................................................... - 35 -

1. INDIVIDUALS ............................................................................................................................................. - 35 -

2. DOMESTIC ENTITIES ................................................................................................................................... - 35 -

3. CONSORTIA .............................................................................................................................................. - 36 -

4. FOREIGN NATIONAL PARTICIPATION FROM COUNTRIES OF CONCERN ................................................................. - 36 -

5. FOREIGN PARTICIPATION CONSIDERATIONS ................................................................................................... - 37 -

B. COMPLIANCE AND RESPONSIVENESS ................................................................................................................... - 37 - C. LIMITATION ON NUMBER OF SUBMISSIONS ..................................................................................................... - 37 - D. COST SHARING ........................................................................................................................................... - 38 -

1. BASE COST SHARE REQUIREMENT ................................................................................................................ - 38 -

2. INCREASED COST SHARE REQUIREMENT ........................................................................................................ - 38 -

3. REDUCED COST SHARE REQUIREMENT .......................................................................................................... - 38 -

4. LEGAL RESPONSIBILITY ............................................................................................................................... - 39 -

5. COST SHARE ALLOCATION ........................................................................................................................... - 39 -https://arpa-e.energy.gov/faqs mailto:ExchangeHelp@hq.doe.gov

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6. COST SHARE TYPES AND ALLOWABILITY ........................................................................................................ - 40 -

7. COST SHARE CONTRIBUTIONS BY FFRDCS AND GOGOS .................................................................................. - 41 -

8. COST SHARE VERIFICATION ......................................................................................................................... - 41 -

III. APPLICATION CONTENTS AND FORMAT .............................................................................................. - 42 -

A. GENERAL APPLICATION CONTENT REQUIREMENTS ................................................................................................ - 42 -

1. MARKING OF CONFIDENTIAL INFORMATION ................................................................................................... - 42 -

2. EXPORT CONTROL INFORMATION ................................................................................................................. - 42 -

B. CONCEPT PAPERS ............................................................................................................................................ - 43 -

1. FIRST COMPONENT: CONCEPT PAPER............................................................................................................ - 43 -

2. SECOND COMPONENT: SUMMARY SLIDE ....................................................................................................... - 44 -

C. FULL APPLICATIONS .................................................................................................................................... - 44 -

1. FIRST COMPONENT: TECHNICAL VOLUME ...................................................................................................... - 44 -

2. SECOND COMPONENT: SF-424 ................................................................................................................... - 45 -

3. THIRD COMPONENT: BUDGET JUSTIFICATION WORKBOOK/SF-424A ................................................................ - 45 -

4. FOURTH COMPONENT: SUMMARY FOR PUBLIC RELEASE .................................................................................. - 46 -

5. FIFTH COMPONENT: SUMMARY SLIDE ........................................................................................................... - 46 -

6. SIXTH COMPONENT: BUSINESS ASSURANCES & DISCLOSURES FORM .................................................................. - 46 -

D. REPLIES TO REVIEWER COMMENTS ................................................................................................................ - 46 -

IV. SUBMISSION REQUIREMENTS AND DEADLINES ................................................................................... - 48 -

A. UNIQUE ENTITY IDENTIFIER AND SAM REGISTRATION ........................................................................................... - 48 - B. USE OF ARPA-E EXCHANGE .......................................................................................................................... - 48 - C. REQUIRED DOCUMENTS CHECKLIST AND DEADLINES ......................................................................................... - 50 - D. COMPLIANCE ............................................................................................................................................. - 50 - E. INTERGOVERNMENTAL REVIEW ......................................................................................................................... - 51 -

V. APPLICATION REVIEW INFORMATION ..................................................................................................... - 52 -

A. RESPONSIVENESS ............................................................................................................................................ - 52 -

1. TECHNICAL RESPONSIVENESS REVIEW ........................................................................................................... - 52 -

2. SUBMISSIONS SPECIFICALLY NOT OF INTEREST ................................................................................................. - 53 -

B. REVIEW CRITERIA ............................................................................................................................................ - 53 -

1. CRITERIA FOR CONCEPT PAPERS ................................................................................................................... - 54 -

2. CRITERIA FOR FULL APPLICATIONS ................................................................................................................ - 54 -

3. CRITERIA FOR REPLIES TO REVIEWER COMMENTS ............................................................................................ - 56 -

C. PROGRAM POLICY FACTORS ......................................................................................................................... - 56 - D. REVIEW AND SELECTION PROCESS ................................................................................................................. - 57 -

1. CONCEPT PAPERS ...................................................................................................................................... - 57 -

2. FULL APPLICATIONS ................................................................................................................................... - 57 -

3. REPLY TO REVIEWER COMMENTS ................................................................................................................. - 57 -

4. PRE-SELECTION CLARIFICATIONS AND “DOWN-SELECT” PROCESS ...................................................................... - 57 -

5. SELECTION FOR AWARD NEGOTIATIONS ........................................................................................................ - 58 -

E. ARPA-E REVIEWERS ....................................................................................................................................... - 58 - F. ARPA-E SUPPORT CONTRACTORS ..................................................................................................................... - 58 - G. RISK REVIEW.............................................................................................................................................. - 59 -https://arpa-e.energy.gov/faqs

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VI. AWARD NOTICES AND AWARD TYPES ................................................................................................. - 60 -

A. AWARD NOTICES ............................................................................................................................................ - 60 -

1. REJECTED SUBMISSIONS ............................................................................................................................. - 60 -

2. CONCEPT PAPER NOTIFICATIONS .................................................................................................................. - 60 -

3. FULL APPLICATION NOTIFICATIONS ............................................................................................................... - 60 -

B. PRE-AWARD COSTS ......................................................................................................................................... - 61 - C. RENEWAL AWARDS ..................................................................................................................................... - 62 - D. FUNDING AGREEMENT TYPES ....................................................................................................................... - 62 -

1. COOPERATIVE AGREEMENTS........................................................................................................................ - 62 -

2. FUNDING AGREEMENTS WITH FFRDCS/DOE LABS, GOGOS, AND FEDERAL INSTRUMENTALITIES .......................... - 62 -

3. OTHER TRANSACTIONS AUTHORITY .............................................................................................................. - 63 -

VII. POST-AWARD REQUIREMENTS AND ADMINISTRATION ...................................................................... - 64 -

A. NATIONAL POLICY REQUIREMENTS .................................................................................................................... - 64 -

1. NATIONAL POLICY ASSURANCES ................................................................................................................... - 64 -

2. ENVIRONMENTAL IMPACT QUESTIONNAIRE ................................................................................................... - 64 -

B. ADMINISTRATIVE REQUIREMENTS ...................................................................................................................... - 65 -

1. COST SHARE PAYMENTS ............................................................................................................................. - 65 -

2. INTELLECTUAL PROPERTY AND DATA MANAGEMENT PLANS ............................................................................. - 65 -

3. U.S. COMPETITIVENESS .............................................................................................................................. - 66 -

4. NONDISCLOSURE AND CONFIDENTIALITY AGREEMENTS REPRESENTATIONS .......................................................... - 67 -

5. INTERIM CONFLICT OF INTEREST POLICY FOR FINANCIAL ASSISTANCE .................................................................. - 68 -

6. COMPLIANCE AUDIT REQUIREMENT .............................................................................................................. - 68 -

7. RESEARCH SECURITY TRAINING REQUIREMENT ............................................................................................... - 68 -

8. TECHNOLOGY PROTECTION PLAN ................................................................................................................. - 69 -

C. REPORTING................................................................................................................................................ - 69 -

1. FRAUD, WASTE, AND ABUSE ....................................................................................................................... - 70 -

2. COMMERCIALIZATION PLAN AND SOFTWARE REPORTING ................................................................................. - 70 -

VIII. OTHER INFORMATION ......................................................................................................................... - 71 -

A. TITLE TO SUBJECT INVENTIONS .......................................................................................................................... - 71 - B. GOVERNMENT RIGHTS IN SUBJECT INVENTIONS.................................................................................................... - 71 -

1. GOVERNMENT USE LICENSE ........................................................................................................................ - 72 -

2. MARCH-IN RIGHTS .................................................................................................................................... - 72 -

C. RIGHTS IN TECHNICAL DATA ......................................................................................................................... - 72 - D. PROTECTED PERSONALLY IDENTIFIABLE INFORMATION ...................................................................................... - 73 -

IX. GLOSSARY ........................................................................................................................................... - 74 -

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BASIC INFORMATION

KEY DATES:

Notice of Funding Opportunity (NOFO) Issue Date: January 15, 2025

Deadline for Concept Paper Questions to ARPA-E-CO@hq.doe.gov: 5 PM ET, February 4, 2025

Submission Deadline for Concept Papers: 9:30 AM ET, February 14, 2025

Anticipated Date for Encourage/Discourage Notifications: 5 PM ET, April 3, 2025

Deadline for Full Application Questions to ARPA-E-CO@hq.doe.gov: 5 PM ET, TBD

Submission Deadline for Full Applications: 9:30 AM ET, TBD

Expected Reviewer Comment Release Date: 5 PM ET, TBD

Submission Deadline for Replies to Reviewer Comments: 5 PM ET, TBD

Anticipated Timeframe for Selection Notifications: July 2025

Anticipated Timeframe for Award: October 2025

Anticipated Period of Performance: October 2025 – October 2028

BASIC INFORMATION:

Total Amount to Be Awarded

Approximately $30 million, subject to the availability of appropriated funds to be shared between NOFOs DE-FOA-0003554 and DE-FOA-0003555.

Anticipated Number and Value of Awards

ARPA-E anticipates making approximately 6-15 awards between NOFOs DE-FOA- 0003554 and DE-FOA-0003555. ARPA-E may issue one, multiple, or no awards under this NOFO. The Federal share of awards under this NOFO may vary between $2 million and $5 million.

Agency Contact Information

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The power grid is currently undergoing a large-scale transformation, including a significant reduction of conventional synchronous generators, a high penetration of inverter-based resources, substantial load growth, and a concerning vulnerability to contingencies and extreme weather. The GRADIENTS program seeks to develop disruptive solutions to drastically improve grid reliability and controllability under these conditions. With the goal of avoiding blackouts and cascading failures, the program will provide new solutions to system operators to facilitate greater controllability and coordination capabilities to stabilize the system under undesired dynamic interactions and extreme weather events.

The GRADIENTS program is composed of three technical categories: (1) Flexible renewable generation,

(2) Intelligent automatic relays, and (3) Wide-area real-time control co-design.

The flexible renewable generation category (Category 1) shall develop inverter-based renewable generators that include (1) inverters that can seamlessly and on-demand transition from grid-following to grid-forming mode and vice-versa, (2) some form of battery-less short-term energy storage for a few https://arpa-e.energy.gov/faqs mailto:ARPA-E-CO@hq.doe.gov mailto:ExchangeHelp@hq.doe.gov mailto:ARPA-E-CO@hq.doe.gov mailto:ARPA-E-CO@hq.doe.gov http://arpa-e.energy.gov/faq mailto:ARPA-E-CO@hq.doe.gov

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- 6 -seconds at rated power, and (3) advanced control solutions to improve grid controllability and coordination in real-time.

The intelligent automatic relays category (Category 2) shall develop advanced relays that include under-frequency/under-voltage load-shedding capabilities for emergency operation smart sensors and algorithms for automatic contingency prediction, small-signal impedance estimation, stability assessment, and incipient fault detection.

The wide-area real-time control co-design category (Category 3) shall develop new real-time control and optimization solutions for energy (inertia) allocation, control authority (damping) allocation, and load-shedding capability allocation across different regions of the grid. These algorithms would be implemented in central/regional control rooms and would interact with the intelligent generation nodes developed under Category 1 and the intelligent relays developed under Category 2.

To effectively respond to this NOFO, expertise and teaming of engineers and scientists from different organizations, disciplines, and technology sectors are expected, especially of those from electrical and mechanical engineering, control engineering, optimization, storage, mathematics, physics, artificial intelligence, and other relevant fields.

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I. FUNDING OPPORTUNITY DESCRIPTION

A. AGENCY OVERVIEW

The Advanced Research Projects Agency – Energy (ARPA-E), an organization within the Department of Energy (DOE), is chartered by Congress in the America COMPETES Act of 2007 (P.L. 110-69), as amended by the America COMPETES Reauthorization Act of 2010 (P.L. 111- 358), as further amended by the Energy Act of 2020 (P.L. 116-260):

“(A) to enhance the economic and energy security of the United States through the development of energy technologies that—

(i) reduce imports of energy from foreign sources;

(ii) reduce energy-related emissions, including greenhouse gases;

(iii) improve the energy efficiency of all economic sectors;

(iv) provide transformative solutions to improve the management, clean-up, and disposal of radioactive waste and spent nuclear fuel; and

(v) improve the resilience, reliability, and security of infrastructure to produce, deliver, and store energy; and

(B) to ensure that the United States maintains a technological lead in developing and deploying advanced energy technologies.”

ARPA-E issues this Notice of Funding Opportunity (NOFO) under its authorizing statute codified at 42 U.S.C. § 16538. The NOFO and any cooperative agreements or grants made under this NOFO are subject to 2 C.F.R. Part 200 as supplemented by 2 C.F.R. Part 910.

ARPA-E funds research on, and the development of, transformative science and technology solutions to address the energy and environmental missions of the Department. The agency focuses on technologies that can be meaningfully advanced with a modest investment over a defined period of time in order to catalyze the translation from scientific discovery to early-stage technology. For the latest news and information about ARPA-E, its programs and the research projects currently supported, see: http://arpa-e.energy.gov/.

ARPA-E funds transformational research. Existing energy technologies generally progress on established “learning curves” where refinements to a technology and the economies of scale that accrue as manufacturing and distribution develop drive improvements to the cost/performance metric in a gradual fashion. This continual improvement of a technology is important to its increased commercial deployment and is appropriately the focus of the private sector or the applied technology offices within DOE. In contrast, ARPA-E supports transformative research that has the potential to create fundamentally new learning curves.

ARPA-E technology projects typically start with cost/performance estimates well above the level of an incumbent technology. Given the high risk inherent in these projects, many will fail to progress, but some may succeed in generating a new learning curve with a projected cost/performance metric that is significantly better than that of the incumbent technology.

ARPA-E will provide support at the highest funding level only for submissions with significant https://arpa-e.energy.gov/faqs mailto:ARPA-E-CO@hq.doe.gov http://arpa-e.energy.gov/

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- 8 -technology risk, aggressive timetables, and careful management and mitigation of the associated risks.

ARPA-E funds technology with the potential to be disruptive in the marketplace. The mere creation of a new learning curve does not ensure market penetration. Rather, the ultimate value of a technology is determined by the marketplace, and impactful technologies ultimately become disruptive – that is, they are widely adopted and displace existing technologies from the marketplace or create entirely new markets. ARPA-E understands that definitive proof of market disruption takes time, particularly for energy technologies. Therefore, ARPA-E funds the development of technologies that, if technically successful, have clear disruptive potential, e.g., by demonstrating capability for manufacturing at competitive cost and deployment at scale.

ARPA-E funds applied research and development (R&D). The Office of Management and Budget defines “applied research” as an “original investigation undertaken in order to acquire new knowledge…directed primarily towards a specific practical aim or objective” and defines “experimental development” as “creative and systematic work, drawing on knowledge gained from research and practical experience, which is directed at producing new products or processes or improving existing products or processes.”1 Applicants interested in receiving financial assistance for basic research (defined by the Office of Management and Budget as “experimental or theoretical work undertaken primarily to acquire new knowledge of the underlying foundations of phenomena and observable facts”)1 should contact the DOE’s Office of Science (http://science.energy.gov/). Office of Science national scientific user facilities (http://science.energy.gov/user-facilities/) are open to all researchers, including ARPA-E Applicants and awardees. These facilities provide advanced tools of modern science including accelerators, colliders, supercomputers, light sources and neutron sources, as well as facilities for studying the nanoworld, the environment, and the atmosphere. Projects focused on early-stage R&D for the improvement of technology along defined roadmaps may be more appropriate for support through the DOE applied energy offices including: the Office of Energy Efficiency and Renewable Energy (http://www.eere.energy.gov/), the Office of Fossil Energy and Carbon Management (https://www.energy.gov/fecm/office-fossil-energy-and-carbon-management), the Office of Nuclear Energy (http://www.energy.gov/ne/office-nuclear-energy), and the Office of Electricity (https://www.energy.gov/oe/office-electricity).

ARPA-E encourages submissions stemming from ideas that still require proof-of-concept R&D efforts as well as those for which some proof-of-concept demonstration already exists.

Submissions can propose a project with the end deliverable being an extremely creative, but partial solution.

1 OMB Circular A-11 (https://www.whitehouse.gov/wp-content/uploads/2018/06/a11_web_toc.pdf), Section 84,

pg. 3.

https://arpa-e.energy.gov/faqs mailto:ARPA-E-CO@hq.doe.gov mailto:ExchangeHelp@hq.doe.gov http://science.energy.gov/ http://science.energy.gov/user-facilities/ http://www.eere.energy.gov/ https://www.energy.gov/fecm/office-fossil-energy-and-carbon-management https://www.energy.gov/fecm/office-fossil-energy-and-carbon-management http://www.energy.gov/ne/office-nuclear-energy https://www.energy.gov/oe/office-electricity

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B. PROGRAM OVERVIEW

1. SUMMARY

The Grid Reliability with Automatic Damping and Inertia for Electrical Networks and Transmission Systems (GRADIENTS) program will support the development of disruptive grid assets and control solutions enabling renewable energy systems to provide and improve services traditionally supported by large conventional synchronous generators.2 At present, existing renewable energy systems without ancillary services can deteriorate grid stability. This program aims to use real-time control co-design (RT-CCD) to transform that problem into a solution, specifically creating intelligent inverter-based resources (IBRs) that improve grid controllability and coordination. The RT-CCD methodology uses control engineering principles throughout the design process rather than considering control design as a subsequent process.3 By co-optimizing assets for power delivery and controllability, this design methodology can achieve improvements in grid stability that are not otherwise possible without prohibitive capital expenses. Projects in this program will cover technologies in three categories: flexible renewable generation, intelligent automatic relays, and wide-area RT-CCD. GRADIENTS technologies based on dynamic metrics that quantify grid stability and controllability in terms of rate of change of frequency (RoCoF), nadir, decay ratio, and recovery time, and the program will also include a techno-economic metric for synergy margin evaluation.

The program will drive advancements in grid resilience, efficiency, and adaptability. By addressing and coordinating resources that can provide inertia (energy) and damping (control) with fast frequency regulation across the grid, GRADIENTS will improve reliability in high-renewable penetration scenarios, mitigating blackout risks, reducing potential curtailment of renewables, lowering operational costs, and maximizing economic viability.4 The program will also foster technological innovation by developing intelligent relays and fault-tolerant protection systems, improving fault detection, adaptability, and response capabilities tailored for IBRs. Furthermore, its scalable and flexible approach to distributed control supports a wide range of applications from large regional grids to localized microgrids with customization for diverse energy mixes and regulatory requirements. Collectively, these advancements will modernize grid infrastructure, promote renewable energy integration, improve grid dynamics, and support a sustainable energy future.

2 The RoCoF, which is the slope or “gradient” of the change of frequency after a contingency, is a fundamental parameter to improve the grid reliability, hence the use of the GRADIENTS acronym.

3 Garcia‐Sanz, Mario. "Control Co‐Design: an engineering game changer." Advanced Control for Applications:

Engineering and Industrial Systems 1, no. 1 (2019): e18.

4 Muir, A., and J. Lopatto. "Final report on the August 14, 2003 blackout in the United States and Canada: causes and recommendations." (2004).

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- 10 -

2. TECHNICAL CHALLENGES

The GRADIENTS program aims to address several grid challenges associated with high penetration of IBRs (Figure 1).

(a) (b)

Figure 1. Electrical contingencies between (a) the United Kingdom and France and (b) Germany and Norway.5,6 Larger frequency oscillations are observed in grids with higher IBR penetration.

• Lack of inertia and damping to manage frequency fluctuation. In conventional grids, large rotating synchronous generators provide inertia (associated to the kinetic energy stored in the rotors) and damping (related to the damper windings of the machines).

Both aspects help reduce oscillations and stabilize the grid during disturbances.

o IBRs lack rotating mass and damper windings, increasing the grid’s susceptibility to frequency fluctuations and potential blackouts.

o IBRs are typically designed to inject the maximum power harnessed from the renewable resource, usually wind or solar, using a grid-following mode. When the grid frequency deviates significantly from the setpoint (60 Hertz [Hz]), IBRs may limit their output or disconnect rather than contribute to frequency regulation, hindering primary control.7

5 GridRadar, UCTE, UKTSOA (https://gridradar.net/en/blog/post/interconnector-trip-fr-uk).

6 Hybrid Greentech. NordLink (https://montelnews.com/news/fcd122d7-8d87-4da8-a0ce-7b126c448ad1/norway-germany-cable-1-4-gw-returns-online-after-failure).

7 Ahmadyar, Ahmad Shabir, Shariq Riaz, Gregor Verbič, Archie Chapman, and David J. Hill. "A framework for assessing renewable integration limits with respect to frequency performance." IEEE Transactions on Power Systems 33, no. 4 (2017): 4444-4453.

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- 11 -o The existing control of IBRs follows a slow response to accommodate existing secondary control time-frames. While advanced control algorithms can emulate inertia and damping, their effectiveness depends on factors like inverter control type, virtual response speed, and coordination among IBRs. Poorly optimized or unsynchronized algorithms can result in slower or less effective responses.

• Lack of integration of voltage regulation capabilities. Voltage ride-through operation is critical to maintain the grid’s voltage profile and prevent instability or equipment failure.8 As grids become more distributed and increasingly rely on IBRs, grid coordination becomes essential to ensure resources operate together without conflict and load-share to meet demands.

o IBRs can typically provide voltage regulation, but these capabilities are not yet integrated into the system-level operations yet.

o Interoperability is also an issue, as the lack of standardized control systems and protocols means IBRs with different characteristics may not function seamlessly as a cohesive system.

o During under-frequency and under-voltage events, traditional grid protection mechanisms, which are designed for synchronous generators, do not work as effectively in systems with high IBR penetration.9,10

• Lack of effective market mechanisms. Market design is increasing in complexity with high IBR penetration. New market mechanisms are needed to integrate renewable generation’s variability and flexibility, including ancillary services markets for frequency regulation, voltage control, and reactive power support, which are traditionally provided inherently by synchronous generators. This will require new methodologies for cost-based dispatch and flexible grid operation, as well as the integration of these markets into tertiary control.

This program also aims to support the development of new protection schemes and decentralized, fast-acting relay systems that can dynamically react to faults and disturbances in real time. The grid must become more flexible to handle the variability and intermittency of renewable resources, which can cause difficulties in balancing supply and demand in real time.11 GRADIENTS will support the development of advanced control co-design solutions based on three categories (Section I.D), along with more sophisticated market mechanisms to ensure grid reliability, stability, and efficiency in a world that is increasingly utilizing variable renewable

8 Li, Chang, Yaqian Yang, Yijia Cao, Lei Wang, and Frede Blaabjerg. "Frequency and voltage stability analysis of grid-forming virtual synchronous generator attached to weak grid." IEEE Journal of Emerging and Selected Topics in Power Electronics 10, no. 3 (2020): 2662-2671.

9 Delfino, Bruno, S. Massucco, A. Morini, P. Scalera, and F. Silvestro. "Implementation and comparison of different under frequency load-shedding schemes." In 2001 Power Engineering Society Summer Meeting. Conference Proceedings (Cat. No. 01CH37262), vol. 1, pp. 307-312. IEEE, 2001.

10 Laghari, J. A., H. Mokhlis, A. H. A. Bakar, and Hasmaini Mohamad. "Application of computational intelligence techniques for load shedding in power systems: A review." Energy conversion and management (2013): 130-140.

11 Li, Chang, Yaqian Yang, Yijia Cao, Lei Wang, and Frede Blaabjerg. "Frequency and voltage stability analysis of grid-forming virtual synchronous generator attached to weak grid." IEEE Journal of Emerging and Selected Topics in Power Electronics 10, no. 3 (2020): 2662-2671.

https://arpa-e.energy.gov/faqs

Questions about this NOFO? Check the Frequently Asked Questions available at https://arpa-e.energy.gov/faqs. For questions that have not already been answered, email ARPA-E-CO@hq.doe.gov (with NOFO name and number in subject line). Problems with

- 12 -energy resources and experiencing dramatic increases in load growth.

GRADIENTS fills a specific technological gap to ensure that IBRs can provide new and improved grid services such as the control co-design of the system with virtual inertia, damping, frequency regulation, and control authority allocation in a distributed, decentralized manner.12,13 The program complements broader efforts in decarbonizing the energy sector while also supporting the expansion of the grid.

3. PROGRAM MOTIVATION

The urgency to address energy leadership and grid resilience is becoming more critical, with governments, utilities, and corporations setting aggressive load growth requirements and decarbonization goals. These targets require large-scale integration of renewable energy systems, which must happen smoothly and without compromising grid reliability. Renewable energy sources like solar and wind are typically connected through inverter-based systems with grid-following control strategies.

Recent advances in power electronics, control algorithms, and communication technologies have opened new possibilities for real-time, decentralized control of IBRs, including new grid-forming control solutions. These technologies make it possible to create more intelligent, autonomous control systems capable of managing large fleets of distributed inverters, allowing IBRs to mimic and improve the stabilizing effects of traditional generators. Technologies like wide-area monitoring systems, fast communication networks, and smart sensors are now available to provide the real-time data needed for improved grid management.14,15 Additionally, advances in machine learning and artificial intelligence can be leveraged to create predictive and adaptive control systems for IBRs.

As the occurrence and severity of extreme weather events such as hurricanes, wildfires, and heatwaves increase, grid resilience is becoming more critical. The 2021 Texas winter storm and recent California wildfires are stark reminders of the vulnerabilities of traditional grid systems and the importance of developing more flexible and resilient solutions.16,17 A decentralized, 12 Cheng, Yunzhi, Lingling Fan, Jonathan Rose, Shun-Hsien Huang, John Schmall, Xiaoyu Wang, Xiaorong Xie et al.

"Real-world subsynchronous oscillation events in power grids with high penetrations of inverter-based resources." IEEE Transactions on Power Systems 38, no. 1 (2022): 316-330.

13 Markovic, Uros, Ognjen Stanojev, Petros Aristidou, Evangelos Vrettos, Duncan Callaway, and Gabriela Hug.

"Understanding small-signal stability of low-inertia systems." IEEE Transactions on Power Systems 36, no. 5 (2021):

3997-4017.

14 Hong, Qiteng, Mazaher Karimi, Mingyu Sun, Seán Norris, Oleg Bagleybter, Douglas Wilson, Ibrahim F. Abdulhadi, Vladimir Terzija, Ben Marshall, and Campbell D. Booth. "Design and validation of a wide area monitoring and control system for fast frequency response." IEEE Transactions on Smart Grid 11, no. 4 (2020): 3394-3404.

15 Peng, Zefeng, Qiao Peng, Yingmin Zhang, Huachun Han, Yue Yin, and Tianqi Liu. "Online inertia allocation for grid-connected renewable energy systems based on generic ASF model under frequency nadir constraint." IEEE Transactions on Power Systems 39, no. 1 (2023): 1615-1627.

16 https://www.ercot.com/news/february2021.

17 https://www.fire.ca.gov/incidents.

https://arpa-e.energy.gov/faqs

Questions about this NOFO? Check the Frequently Asked Questions available at https://arpa-e.energy.gov/faqs. For questions that have not already been answered, email ARPA-E-CO@hq.doe.gov (with NOFO name and number in subject line). Problems with

- 13 -inverter-based grid with robust real-time control can improve resilience by ensuring that local resources can operate autonomously or in coordination with the larger grid even in the face of widespread grid failures.

The GRADIENTS program transforms and reimagines the role of IBRs. By enhancing the intelligence of IBRs, the program seeks to transform existing challenges into assets that strengthen system stability, reliability, and resilience. This involves co-designing IBRs with storage systems and embedded autonomous decision making, developing intelligent and cooperative relay technologies for fault-tolerant protection, and integrating these capabilities into advanced wide-area control tools. The GRADIENTS program disrupts the traditional methodology of prioritizing optimal power output and retroactively addresses reliability issues without costly capital expenditures and increased reliance on synchronous generators. In doing so, the program leverages the growth of renewables to enhance grid reliability and empowers renewables to actively participate in emerging ancillary services markets, supporting the evolution of a more flexible and sustainable energy grid.

4. TECHNICAL DESCRIPTION

The key equation in power system stability analysis is the rotational inertia equation (swing equation), which describes the effect of the imbalance between the electromagnetic output torque and the mechanical input torque of individual rotating machines.18 In stability studies for the power grid, the mechanical characteristics of the synchronous generator are represented by parameters such as the moment of inertia and damping. The swing equation, described by second-order dynamics of a synchronous generator, can be represented by the transfer function P(s) between the angular position ( ) of the rotor and the difference between the mechanical input torque (Tm) supplied by the prime mover and the electrical output torque (Te) of the generator (see equation 1, where J is the moment of inertia of the rotor in [kgm2], D is the damping coefficient [Nms/rad], and K is the synchronizing power coefficient [Nm/rad]). The kinetic energy (Estored = Ekinetic) in a synchronous generator is stored in its rotating mass (rotor) and plays a critical role in power system dynamics and stability. It is calculated based on the moment of inertia (J) and the angular speed of the rotor (ω = d /dt) (see equation 2). The inertia constant (H) is commonly used to characterize the stored energy in a synchronous generator, representing the time the generator can supply rated power (Prated) from its stored kinetic energy, which is typically a few seconds (see equation 3).

𝜃(𝑠)

𝑇𝑚(𝑠)−𝑇𝑒(𝑠) = 𝑃(𝑠) =

𝐽 𝑠2+𝐷 𝑠+𝐾 (1)

𝐸𝑠𝑡𝑜𝑟𝑒𝑑 = 𝐸𝑘𝑖𝑛𝑒𝑡𝑖𝑐 = 0.5 𝐽 𝜔2 [𝐽𝑢𝑙] (2)

𝐻 = 𝐸𝑠𝑡𝑜𝑟𝑒𝑑

𝑃𝑟𝑎𝑡𝑒𝑑 [𝑠𝑒𝑐𝑜𝑛𝑑𝑠] (3)

18 Prabha Kundur, “Power System Stability and Control”, McGraw-Hill, New York, 1994.

Questions about this NOFO? Check the Frequently Asked Questions available at https://arpa-e.energy.gov/faqs. For questions that have not already been answered, email ARPA-E-CO@hq.doe.gov (with NOFO name and number in subject line). Problems with

- 14 -

These two characteristics (inertia and damping) help stabilize the grid frequency during sudden disturbances or power imbalances. IBRs, on the other hand, do not have a rotating mass or damper windings and typically do not provide these stabilizing effects, making the grid more susceptible to frequency fluctuations and potential blackouts. GRADIENTS tackles stability challenges in power grids with high penetration of IBRs by enhancing both inertia (energy buffer) and damping (control capabilities).

As an example, Figure 2 shows the simulation of the swing equation of a synchronous machine, modeled as a second order system, with three cases that represent various inertia and damping parameters. The figure shows that increasing inertia (J) improves M1 (reducing the normalized RoCoF and nadir) but deteriorates M2 (increasing the normalized decay ratio and recovery time). Improving both dynamic characteristics requires not only more inertia (J), but also more damping (D), as is shown in Case 3. More information about the M1 and M2 variables can be found in Section I.E.1.

Figure 2. Results of three cases: Case 1 (J = 1, D = 0.3), Case 2 (J = 3, D = 0.3), and Case 3 (J = 3, D = 1.5). Figure (a) represents M1, or short-term metric (normalized RoCoF and nadir), versus M2, or recovery-term metric (normalized decay ratio and recovery time), and Figure (b) shows the frequency oscillation over time with these three cases.

C. PROGRAM OBJECTIVES

The overall objective of the GRADIENTS program is to develop innovative and disruptive technologies that enable real-time power grid management via flexible renewable generation, intelligent and automatic relays, and system-wide real-time control…