Grid-Forming PV Inverter: Opportunities and Challenges

1. Grid-Forming PV Inverter: Opportunities and Challenges NSF Workshop on Power Electronics-Enabled Operation of Power Systems Oct 31 – Nov 1, 2019 Hariharan Krishnaswami, Ph.D., Technology Manager, Systems Integration

2. Solar Energy Technologies Office WHAT WE DO The Solar Energy Technologies Office funds early-stage research and development in three technology areas: photovoltaics, concentrating solar power, and systems integration with the goal of improving the affordability, reliability, and performance of solar technologies on the grid. HOW WE DO IT Research and development to address integration of solar to the nation’s electricity grid. Relevant and objective technical information on solar technologies to stakeholders and decision-makers. Cutting-edge technology development that drives U.S.s leadership and supports a growing and skilled workforce.

3. SETO Systems Integration Research The Systems Integration (SI) subprogram supports early-stage research, development, and field validation that advances the reliable, resilient, secure and affordable integration of solar energy onto the U.S. electric grid.

4. A System Approach for Solar Grid Integration Research • (Energy, Capacity, Ancillary Services, Essential Reliability Services, Resilience) • (LT Resource Planning, Day-Ahead Operation, Real-time Operation, Emergency Event Operation) • (PV & Power System Models, State Estimation, Optimal Power Flow, Data Ingestion, Interoperability, Cybersecurity, Visualization) • (Power Electronics, Solar Forecasting, Energy Storage, Data Analytics & Machine Learning, Communication, Control, Sensors, Computing)

5. Colloboration across DOE • Systems Integration program also actively participates in the Grid Modernization Initiative, a DOE office-wide initiative • Ref.: U.S. Department of Energy Grid Modernization Initiative. https://energy.gov/under-secretary-science-andenergy/grid-modernization-initiative • Collaboration with DOE Office of CyberSecurity, Energy Security and Emergency Response • Ref.: U.S. Department of Energy Office of Electricity Delivery & Energy Reliability. Multiyear Plan for Energy Sector Cybersecurity. https://www.energy.gov/sites/prod/files/2018/05/f51/DOE%20Multiyear%20Plan%20for%20Energy%20Sector%20Cybersecurity%20_0.pdf

6. Advanced Power Electronics Design for Solar Applications • Topic 1 projects focus on advancing inverter/converter technology that lowers lifetime costs by reducing upfront costs, extending product life, improving efficiencies and lowering manufacturing costs. • Topic 2 projects are exploreing enhanced grid integration capabilities https://www.energy.gov/eere/solar/advanced-power-electronics-design-solar-applications-power-electronics

7. Solar Energy Technologies Office FY2019 Funding Program Solar Energy Technologies Office FY2019 Funding Program $130 Million for Advanced Solar Energy Research The U.S. Department of Energy Solar Energy Technologies Office is looking to fund up to 80 projects that lower the cost of photovoltaic and concentrating solar-thermal power technologies, improve grid integration, develop manufacturing solutions, and lower soft costs by reducing regulatory burdens. Funding Opportunity Topic Areas • Photovoltaics Research and Development • Concentrating Solar-Thermal Power Research and Development • Balance of Systems Soft Costs Reduction • Innovations in Manufacturing – Hardware Incubator • Advanced Solar Systems Integration Technologies

8. Topic Area 5.3B: Advanced Controls for Grid-Forming Inverters • The main objective of this topic is to develop and field-validate next-generation grid-forming smart PV inverters that can collectively establish frequency, maintain voltage magnitude, provide stability, and enable black start in a distribution feeder with high penetration of PV. • Modeling, control, coordination, and field validation of grid-forming PV inverters at scale • Coordinated control between grid-forming and grid-feeding inverters • Control tactics for 100% inverter-based generation in resilient microgrids • Distributed stability controls integrated with grid-forming PV inverters • Studies on performance of grid-forming PV inverters under grid fault scenarios

9. Topic Area 5.3B: Advanced Controls for Grid-Forming Inverters • Suggested Metrics in FOA • Field demonstrations should coordinate with more than 20 PV inverters • varying mix of grid-following and grid-forming functions with DER instantaneous penetration of 90% or higher • frequency variations within ±0.5 hertz under load variations ranging from 10% to 100% of full load at different time scales • Black-start functionality should be able to perform without help from rotating generators • Scalability must be proved theoretically and verified using simulation for different aspects that include more than 100 inverters and more than 1,000 nodes • Demonstrations of particular interest include large-scale testing with multiple grid-forming inverters, DER, and dynamic loads with a combined power rating of more than 100 kilowatts

10. Awardee Success Story: Stabilizing the Power System in 2035 and Beyond: Evolving from Grid-Following to Grid-Forming Distributed Inverter Controllers 2016-2019 BACKGROUND The team developed new virtual oscillator controls for set of grid forming inverters with no communications Analysis of stability tipping point under high penetration of grid-following inverters Testing and Validation of grid-forming inverter controls. Research Roadmap on Grid-forming Inverters (currently in draft) • The aim of the proposed project is to develop distributed inverter controllers which provide a low-resistance path from the current inertia-dominated grid paradigm to a future grid paradigm dominated by low-inertia power systems with 100's of GWs of PV integration. SUCCESS Team: National Renewable Energy Laboratory, University of Washington, University of Minnesota

11. Research Roadmap on Grid Forming Inverters (Draft) Joint effort by: National Renewable Energy Laboratory, Lawrence Berkeley National Laboratory, Sandia National Laboratories, University of Washington, University of Wisconsin, US Department of Energy, Solar Energy Technologies Office Total annual and instantaneous inverter-based wind and solar generation based on power system size (Kroposki 2019).

12. Thank you! Hariharan Krishnaswami, Technology Manager Hariharan.Krishnaswami@ee.doe.gov Solar Energy Technologies Office