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Energy Systems Integration News

A monthly recap of the latest happenings at the Energy Systems Integration Facility and developments in energy systems integration (ESI) research at NREL and around the world.

June 2017

Read the latest ESI news from NREL.

Rooftop solar panels

NREL Researchers to Estimate and Observe Grid Impacts of the August Solar Eclipse

A total solar eclipse will cut a narrow path across the breadth of the United States on August 21, 2017, bringing the first total eclipse to the contiguous states for nearly 40 years. But that narrow path of totality brings with it a much broader swath of partial blockage of the sun that will affect all of the country except Hawaii.

When the shadow of the last total solar eclipse swept across the Pacific Northwest back in 1979, the lack of interconnected solar power meant that it had a minimal impact on the grid. But because that situation has changed dramatically, NREL researchers will be keeping close tabs on the August eclipse to see how the grid reacts.

The NREL project includes a pre-event analysis on how the eclipse will affect the output of solar photovoltaic (PV) systems across the Western Electricity Coordinating Council (WECC) territory—that is, the western half of the U.S. power grid. Supported by the U.S. Department of Energy’s (DOE's) SunShot Initiative, NREL will receive data from Peak Reliability, which manages grid reliability for all or parts of 14 Western states; British Columbia, Canada; and the northern portion of Baja California, Mexico.

NREL will focus on understanding the spatial and temporal profile of the eclipse and how the PV output across the WECC will be affected. While the size and location of utility-scale PV sites are known and their outputs are monitored, rooftop PV systems pose a greater challenge for grid operations because their size and location are often unknown. NREL will use databases of distributed PV sites developed through previous efforts to determine how much distributed PV is present at the substation level and then estimate the impact of the eclipse on their output.

NREL researchers will apply the predictions of reduced PV output to expected baseline grid conditions on the day of the eclipse to determine if new generation schedules and power dispatches are needed. WECC system models will then determine the critical operating times for the grid, Peak Reliability will use those models to perform contingency analyses, and Peak Reliability and NREL will develop any needed mitigation measures.

During the eclipse, NREL will use two large PV arrays at the National Wind Technology Center to monitor performance and verify simulations. Denver will experience a 92% solar eclipse, so the impact should be significant. Meanwhile, Peak Reliability will provide NREL with a wide assortment of grid data collected during the event, to validate the pre-event analysis. The results will be used by utilities and Peak Reliability to gain some insight into how much distributed PV is present on their systems at the substation level. It will also result in a validated framework for studying the impact of wide-area disturbances, such as large storms, through their geospatial profile on grid operations.

Welcome Juan Torres, New Energy Systems Integration Lead

On June 5, Juan Torres took over as the new Associate Laboratory Director for Energy Systems Integration at NREL.

An electrical engineer, Torres worked for the U.S. Department of Energy's Sandia National Laboratories for 27 years. Most recently he served as deputy to the vice president for energy and climate programs.

In his role at NREL, Torres will oversee continuing efforts at the laboratory's Energy Systems Integration Facility (ESIF) to strengthen the security of the nation's electrical grid, to increase the use of renewable sources of energy, and to develop and demonstrate new technologies to modernize the power grid.

"I'm excited about returning to my home state of Colorado to tackle U.S. energy challenges at the nation's premier advanced energy lab," Torres said. Read the full press release.

Heila Technologies to Test Plug and Play Microgrid Controller at ESIF

In 2016, Heila Technologies, a startup company founded by several Massachusetts Institute of Technology students and alumni, won the DOE's Cleantech University Prize for their work on an innovative microgrid controller that can simplify the building and management of microgrids. Now, as part of their first place prize, Heila Technologies is partnering with NREL to test their microgrid controller—Heila IQ—in the ESIF. Using NREL's recently developed Consolidated Utility Base Energy (CUBE) microgrid platform, Heila IQ will demonstrate its ability to maximize efficiency and maintain stability while controlling a variety of energy sources.

"We chose to work with NREL's CUBE system because we don't have in-house access to the expert staff and military-grade equipment required to test our proprietary control algorithms," said Albert Chan, a Heila Technologies co-founder. "Through this testing, we hope to gain experience in managing military-grade equipment and to showcase our controller's ability to maintain reliable and high-quality power."

NREL Papers on Solar Forecasting, Feeder Models Named "Best Papers" by IEEE PES

Two papers by NREL researchers earned "best paper" for the IEEE Power & Energy Society General Meeting that will take place in Chicago, Illinois, on July 16–20, 2017. The papers advance research on ultra-short-term solar forecasting and reduced-order feeder models.

  • NREL, IBM, and the University of Texas at Dallas, co-authored "Short-term Global Horizontal Irradiance Forecasting Based on Sky Imaging and Pattern Recognition." The paper details new methods for classifying data from Cloud Sky Imagers, and translating that information into accurate ultra-short-term solar power forecasts. Using this method, the authors demonstrated the ability to significantly improve on the one-hour-ahead forecasting persistence benchmark. This work was supported by the DOE's Solar Energy Technology Office-Systems Integration Program.
  • NREL and Hawaiian Electric Company (HECO) engineers co-authored "Network Reduction Algorithm for Developing Distribution Feeders for Real-time Simulators." This paper describes a newly developed method for adapting distribution feeder models for use in hardware-in-the-loop (HIL) experiments. Using this method, a full feeder model is simplified down into a reduced-order model that can be solved in real-time. Selected nodes of interest, such as the locations of PV systems, capacitor banks, or smart grid devices, are preserved so that the reduced-order model accurately represents the dynamics of the full feeder. This work was funded by HECO and the DOE Grid Modernization Initiative.

Graduate Interns to Develop New Research Capabilities at the ESIF

Eight graduate students have arrived at the ESIF for the Energy Systems Integration (ESI) Summer Graduate Development Program, designed to stimulate interest in interdisciplinary energy systems studies by providing the opportunity to carry out research and development projects from a broad range of ESI disciplines.

The students bring a variety of backgrounds in science and technology and come from universities across the country—including University of Massachusetts, University of Colorado Boulder, University of California Berkeley, Arizona State University, Virginia Tech, Stanford University, and the University of Washington Seattle.

In an effort to expose this summer's cohort to the breadth of ESI topics, each student will perform work on a project that contributes to the development of new ESIF capabilities. Project areas include:

  • Energy System Analytics and State Estimation
  • Advanced Distribution Management Systems Applications and Evaluation
  • Defining Technology Requirements for Future Smart Homes
  • Microgrid Controller Cybersecurity Test Plan Development
  • Dispersive Technology Software Defined Network Demonstration
  • Scheduling Energy Storage Operation and Field Demonstration
  • Spatial-Temporal Models for Interdependence of Solar Irradiance and Power Consumption of Thermostatically Controlled Loads
  • Inter-Annual Variability of Wind and Solar Resources.

Each student has been assigned to an ESI mentor in their specific area of research and interest. They will be at NREL for eight weeks.

ESI Journal Articles Examine Wind Turbine Controls for Grid Support and Analyze Ramping Events

ESI's Eduard Muljadi contributed to two papers on wind turbine controls that were recently published, both of which examined the use of Double Fed Induction Generators (DFIGs) in wind turbines. DFIGs are currently the most popular concept used in wind power generation. They are controlled by power electronics converters, allowing them to both import and export real and reactive power independently and instantaneously, thus helping to support the grid effectively during disturbances.

The first paper, "Disturbance-Adaptive Short-Term Frequency Support of a DFIG Associated With the Variable Gain Based on the ROCOF and Rotor Speed," proposes an additional control loop to improve frequency support while ensuring stable operation. The second paper, "Power-Smoothing Scheme of a DFIG Using the Adaptive Gain Depending on the Rotor Speed and Frequency Deviation," also proposes an additional control loop, this time to smooth the wind turbine's output power without slowing the rotor excessively.

ESI's Anthony Florita and Bri-Mathias Hodge also contributed to the paper, "Characterizing and Analyzing Ramping Events in Wind Power, Solar Power, Load, and Netload," which found that ramping characteristics are significantly different between load and netload, even at a low renewable penetration of 5.45%. Netload is defined as the total electric demand in the system minus wind and solar power production. The study concluded that, under certain circumstances, up-ramping load while down-ramping renewable energy sources (or vice versa) can create more severe netload ramping events.

Where in the World are Our ESI Researchers?

A month rarely goes by where our ESI researchers and leadership aren't traveling the country to share their knowledge—and learn from others, of course. In May, you could've tracked down three of our researchers—Murali Baggu, Yingchen Zhang, and Vahan Gevorgian—participating in the Phase II: First Climate Change Working Group Smart Grids Workshop, held at the Energy Department’s Argonne National Laboratory on May 16 and 17. Baggu and Zhang presented on a proposed process to implement cooperative, mutual product verification and qualification testing between China and the United States. Gevorgian discussed NREL's experience in implementing mutual verification and testing with other countries. A delegation from China also toured the ESIF and National Wind Technology Center on May 18.

On June 8, you could have again found Baggu in a panel called "What Makes Grids Smart?" at the Schweitzer Engineering Laboratories' Modern Solutions Power Systems Conference held June 7–9 in Chicago, Illinois. Baggu discussed renewable energy's challenges and opportunities regarding the smart grid. On June 21, Matt Futch, NREL's global business development director, spoke at VERGE Hawaii: Asia Pacific Clean Energy Summit, which focused on how Hawaii can meet its ambitious mandate of 100% renewable energy by 2045. The summit was held June 20–22 in Honolulu, Hawaii.

On June 22, Baggu was on the road again, participating in the panel "The Digital Grid—Democratizing the Grid to Support the DER Ecosystem” for the GE Grid Software Solutions Americas User Conference, held June 19–22 in Bellevue, Washington. Baggu wrapped up the month in Scottsdale, Arizona, on June 26, participating in a panel titled “Perspectives on Benefits of the Microgrid Solution” for the “Microgrids for Utilities, Communities and Cities" Workshop as part of the IDEA2017: Sustaining Our Success annual conference and trade show, held June 26–29 in Scottsdale, Arizona.

Three ESI researchers also presented technical papers at the 44th IEEE Photovoltaic (PV) Specialists Conference, held June 25–30 in Washington, D.C., Barry Mather presented a quasi-static, time-series approach to analyzing the operation of a distribution circuit with high penetrations of PV systems, significantly shortening the computation time and effort needed. Mike Dooraghi tackled solar resource assessment with two papers: one comparing instruments used to measure plane-of-array solar irradiance of one-axis tracking PV systems and another exploring the modeling and design optimization of systems that combine PV panels with concentrating PV systems. Finally, Yu Xie discussed recent advancements in the numerical simulation of surface irradiance for solar energy applications.

Calling for Facility User Allocation Requests

NREL provides access to the ESIF as a national user facility to study clean energy technologies at all scales—from developing and validating appliances to running multi-megawatt-sized grid simulations. On behalf of DOE, NREL runs an annual call for requests in which research and development projects can request the use of ESIF resources at NREL. Projects that are funded by DOE offices or aligned with DOE and NREL's mission are eligible to use these resources.

Learn more about criteria for allocation requests and how to submit proposals online. Submissions are due no later than August 1, 2017.

Look Out for NREL Staff at APRISE 2017

NREL staff members Martha Symko-Davies, Murali Baggu, and Sam Booth will be participating in two panel discussions at the Asia Pacific Resilience Innovation Summit and Expo (APRISE) on July 19-20 in Honolulu, Hawaii. Over the course of the two-day conference, speakers and panelists will focus on the planning, design, justification, and implementation of energy-secure and resilient microgrid designs. Panel topics include security and resilience metrics, design methods and tools, and the integration of cyber and physical security with utility systems.

Baggu, group manager of the ESIF's power systems operations and control group, will be a panelist for two sessions. The first will explore the DOE labs' perspectives on microgrid design and research needs and will be chaired by Symko-Davies, director of partnerships for energy systems integration. The second will be a case study panel about the lab's Miramar base microgrid deployment work, chaired by Booth, engineered with NREL's Integrated Applications Center.

The summit is designed to bring together a variety of perspectives from the U.S. Department of Defense, DOE, national laboratories, universities, communities, utilities, and industry to explore the opportunities and challenges in resilient microgrid design.

Attending the IEEE PES General Meeting? NREL researchers will be presenting.

If you're attending the IEEE PES General Meeting in Chicago, Illinois, don't miss these two panel presentations, which include talks from NREL energy systems integration researchers:

  • "Modeling, Simulation, and Control of Distributed Energy Resources" – This panel, which includes Brian Johnson of NREL, will discuss the modeling, simulation, and control of distributed energy resources for both utility-scale grids and microgrids.
  • "Big Data Access and Big Data Research Integration in Power Systems" – This panel, which includes Yingchen Zhang of NREL, will explore the challenges of and methods for gathering big data for power systems research.