Energy Systems Integration News
A monthly recap of the latest energy systems integration (ESI) developments at NREL and around the world.
Read the latest ESI news from NREL.
NREL Study Finds Integrated Utility Control Can Improve Grid Voltage Regulation Beyond Advanced Inverters Alone
A new study performed by NREL, GE Grid Solutions, and Duke Energy has found that when a large solar photovoltaic (PV) system is connected to the electric grid, a centralized control system at the utility can regulate the voltages on the grid's distribution feeder lines better than advanced inverters alone. The project combined advanced software simulation, novel 3-D visualization, and lab-based hardware testing at megawatt scale, all enabled by the one-of-a-kind capabilities of NREL's Energy System Integration Facility (ESIF).
Duke Energy's grid has a large, 5-megawatt (MW) PV system interconnected to a line about 2 miles from the substation. The peak demand on the line is also about 5 MW, so at times more PV power is being fed into the line than is being used, leading to voltage control issues and causing the power to reverse flow back into the substation. The unstable voltages and reversed flows can potentially damage customer's devices and interfere with utility operations.
The modeling of Duke Energy's feeder line examined how effective inverter-based volt/VAR control would be versus a centralized, utility-controlled advanced distribution management system (ADMS), provided by GE Grid Solutions. While the advanced inverters provided some level of local volt/VAR control—particularly in hypothetical scenarios with more PV further from the substation—the ADMS provided integrated volt/VAR control (IVVC), which noticeably improved operations by reducing voltage challenges and equipment wear and tear. The ADMS also provided conservation voltage reduction (CVR), a scheme to reduce power demand by slightly lowering the voltage on a feeder line.
The research team built a computer model of the feeder line and carried out simulations of system operations over time, used advanced visualizations to understand the results, connected an actual 500-kVA inverter to a full-scale feeder simulation for a real-time simulation, and carried out cost-benefit analyses of each control method.
The project found that all tested configurations of ADMS-controlled IVVC with CVR provided improved performance and operational cost savings compared to the local control modes. Specifically, IVVC with a power factor of 0.95 proved the technically most effective voltage management scheme for the system studied. This configuration substantially reduced the need for utility equipment to regulate the voltages, and also reduced the observed voltage challenges on the feeder line.
EPRI, Schneider Electric Demonstrate Framework for Distributed Resource Communications
Researchers from the Electric Power Research Institute (EPRI) and Schneider Electric are working with NREL staff at the Energy Systems Integration Facility (ESIF) to demonstrate communications with distributed resources through the EPRI distributed energy resource management system with the Schneider advanced distribution management system (ADMS). The aim is to develop the communication, information, and computation (CIC) layers that support system-level grid control. The CIC framework includes an enterprise integration test environment, a commercial ADMS, open software platforms, an open-platform home energy management system, communication modules, and applications.
EPRI began testing its open-source CIC infrastructure, which is enabling the team to improve the interoperability of multiple clean technology devices in a secure fashion. The installed equipment included a simulated line feeder technology representing 10 miles, which ensures that the system architecture is consistent with that of an electric utility. The Schneider Electric ADMS was configured in the lab and began to provide the current network state, including voltage values and alarms, leveraging real-time data along with state estimation and load-flow analyses. The research setup used the ESIF's solar PV simulator and connected devices in the Systems Performance Laboratory. This is the first time the Schneider ADMS has been configured and demonstrated to support this type of operation, and the project partners are actively working to increase the innovation already achieved.
The project is one of five partnerships NREL is managing under the Integrated Network Testbed for Energy Grid Research and Technology Experimentation (INTEGRATE) project, which aims to address the challenge of enabling the nation's electric grid to handle increasing amounts of renewable energy. See the NREL news release on INTEGRATE.
ESI Researchers Publish Two Papers in IEEE Transactions on Smart Grids
NREL's ESI researchers are gaining notice in the smart grid arena with the recent publication of two technical articles in IEEE Transactions on Smart Grids. Emiliano Dall'Anese is one of the authors of "Scalable Optimization Methods for Distribution Networks with High PV Integration," which proposes a suite of algorithms to determine the active- and reactive-power set points for photovoltaic (PV) inverters in distribution systems. The objective is to optimize the power flow while keeping voltages within nominal limits, but nonlinear power-flow constraints make these calculations computationally intensive. The authors, including engineers from the University of Minnesota and the University of British Columbia, applied approximations and simplifications to reduce the problem to a linearly constrained quadratic program, which is much easier to solve.
The second article, "Distributed MPC for Efficient Coordination of Storage and Renewable Energy Sources Across Control Areas," authored by Kyri Baker with several coauthors from Carnegie Mellon University, examines how renewable energy resources and the use of energy storage can be coordinated across grid control areas. The article specifically examines a case wherein one control area has a large amount of renewable resources and its neighbor has a large energy storage capacity. The problem becomes one of model predictive control, also known as look-ahead optimization: the power flows need to be optimized based on a model's prediction of the future. The authors derived an approach that allows each control area to quickly iterate toward the optimal solution while only exchanging information about each solution at the buses between the control areas. This means that control areas can coordinate such energy resources without having to share internal details about the operation of their grid.
ARPA-E Director Examines Deep Decarbonization of Energy Supplies
Tim Heidel, program director for the Advanced Research Projects Agency-Energy (ARPA-E), discussed "Research Needs in Power Systems for Achieving Deep Decarbonization" at NREL on October 25, 2016, as part of NREL's Energy Systems Integration seminar series.
Drawing on the report "Pathways to Deep Decarbonization in the United States"—published by Energy and Environmental Economics, Inc. in collaboration with DOE's Lawrence Berkeley National Laboratory (LBNL) and Pacific Northwest National Laboratory—Heidel noted that to cut greenhouse gas emission levels to 80% below 1990 levels by 2050 would require high levels of energy efficiency, the decarbonization of electricity supplies, the electrification of most end uses, and the switching of the remaining end uses to lower-carbon fuels. The high penetrations of renewables needed to decarbonize the power supply, combined with the electrification of most end uses, will create unique challenges for electric grids of the future.
To address those challenges, Heidel suggested a need for three tools:
- Improved system state awareness and visibility
- Power flow control and dispatchable loads
- Faster, scalable algorithms for optimizing operations.
As examples of ARPA-E projects that addressed the need for improved awareness and visibility, Heidel listed LBNL-developed micro-synchrophasors for monitoring distribution systems as well as a cyber-physical security assessment developed by the University of Illinois atUrbana-Champaign.
For power flow control, Heidel introduced the "distributed series reactor," an electromagnetic device clamped onto transmission lines that can add impedance to direct the power flows on the grid. The device can solve transmission bottlenecks at half the cost of other approaches. In addition, a device called the "compact dynamic phase angle regulator," located at the substation, allows operators to shunt power to another feeder. And AutoGrid has developed a highly dispatchable, distributed demand response package to reduce loads.
ARPA-E is also addressing power flow control through a new program called Network Optimized Distributed Energy Systems (NODES), which will leverage distributed energy resources and flexible loads for grid services. NODES awarded $33 million to 12 projects in December 2015, including an NREL project for real-time optimization and control of next-generation distribution architecture.
For optimization algorithms, Heidel pointed to transmission topology control algorithms, which can take lines in and out of service to achieve optimal topologies. Although the approach seems crude relative to devices that control power flow, studies have indicated production cost savings of more than $100 million per year, which is more than half the cost of congestion, while reducing renewable energy curtailments by 40% or more. Heidel also suggested that natural gas and electricity co-optimization is of growing importance as the grid depends more heavily on natural gas.
To close out the discussion, Heidel turned to the problem of optimal power flow (OPF). He claimed that no current tool can fully take advantage of all the network opportunities for optimization. One issue is that existing public OPF R&D data sets aren't adequate because they need to use real data, but when such data is obtained, it often can't be published or verified.
For this reason, ARPA-E has established a program called Generating Realistic Information for the Development of Distribution and Transmission Algorithms, or GRID DATA, which aims to create open-access, large-scale, realistic, and validated grid models. Heidel noted that ARPA-E plans to launch a Grid Optimization Competition to find the best way to benchmark and compare OPF models.
DOE Lab-Bridge Program to Include a Microgrid Innovation Challenge
The U.S. Department of Energy (DOE) announced on September 28 the launch of a new program called Lab-Bridge, which aims to reduce the barriers to collaboration between DOE's 17 national laboratories and the private sector. NREL is playing a leading role by developing a coordination strategy to share the lessons learned in the program and to maximize its impact. The pilot program includes the Microgrid Innovation Challenge, which will bring partners together to demonstrate effective microgrid controller solutions to specific challenges.
The challenge calls for near-commercial microgrid controllers to demonstrate an ability to actively stabilize the grid, minimize outages via automated self-healing while operating within a distribution system, achieve high-precision regulation of the microgrid voltage and frequency, perform intelligent load prioritization and rebalancing when there is insufficient power generation, and transform highly variable renewable sources into assets instead of liabilities.
The top eight applicants will have a chance to test their controllers in the Energy Systems Integration Facility (ESIF) using a power hardware-in-the-loop configuration that combines hardware with modeled real-world grid scenarios. They will then have about three months to improve their technologies, returning to the ESIF for a final evaluation that will result in a prize for the best-scoring controller. For more information on Lab-Bridge and the Microgrid Innovation Challenge, see the blog post by Deputy Secretary of Energy Elizabeth Sherwood-Randall and the NREL press release.
Innovation Magazine Puts a Spotlight on NREL Cybersecurity Test Bed
The fourth quarter 2016 issue of Innovation magazine includes an article about NREL's Cyber Physical Systems Security and Resilience Center, with a particular focus on the Test Bed for Secure Distributed Grid Management, also known as the cybersecurity test bed. The article, "Defending the Power Grid from Hackers," notes recent test bed work with Splunk, Dispersive Technology, and Honeywell. Splunk has created a dashboard that creates greater situational awareness of cyberattacks for system operators.
NREL ESI Engineers Travel the Globe to Share Research
NREL ESI Engineer Barbara O'Neill has been doing some globe-trotting recently to help governments transition to cleaner energy sources. Hawaii, for instance, has been a leader in clean energy since it established the Hawaii Clean Energy Initiative (HCEI) with the U.S. Department of Energy (DOE) in 2008. After initially setting a goal of 70% clean energy by 2030, the state upped the ante in 2015, setting a goal of 100% renewable electricity by 2045. The DOE Office of Energy Efficiency and Renewable Energy (EERE) has established the Energy Transition Initiative (ETI) to help islands, states, and cities transition to a clean energy economy and achieve their clean energy goals, and the ETI has worked with Hawaii since the HCEI was established.
Recognizing a need to build internal capacity at the Hawaii Public Utilities Commission (PUC), NREL delivered training this summer to help staff keep pace with the changes. Building on energy systems basics training that NREL provided to PUC staff in August 2015, O'Neill and NREL Engineer Emerson Reiter spearheaded a follow-on, two-day training in July 2016 that focused on more advanced topics, such as energy modeling. On the first day, attendees explored a variety of future energy scenarios (such as high fuel prices) and then examined the societal costs of each scenario. The second day focused on simplified distribution system models that allowed the PUC staff to see how photovoltaic systems could affect the voltage profile of a feeder. See the EERE blog post on the visit.
O'Neill and NREL Engineer Ian Baring-Gould also went to Bangkok, Thailand, in late October 2016 to meet key Pakistan government personnel for an Integrated Energy Planning (IEP) workshop. The workshop was primarily facilitated by the Pacific Northwest National Laboratory, but NREL, Sandia National Laboratories, and Argonne National Laboratory also had predominant roles. The NREL representatives facilitated a session that created a vision statement for the IEP process while also providing an overview of grid integration. O'Neill also hosted a breakout session for those more interested in utility-scale grid integration. The workshop was very successful, and O'Neill hopes to continue the momentum through an upcoming visit to Pakistan's capital city of Islamabad.
NREL ESI Engineer Murali Baggu attended the sixth Climate Change Working Group (CCWG) Smart Grids Workshop on November 2–4, 2016, in Kylin Villa, Shenzhen, China. The workshop was co-organized by China's National Energy Administration and DOE. It included a technical tour of the Qianhai Smart Grid Pilot project, one of the four collaborative demonstration projects being carried out as part of the CCWG Smart Grids action initiative.
New DOE Solar Funding Presents Opportunity to Partner with NREL
The U.S. Department of Energy (DOE) Solar Energy Technologies Office Technology-to-Market program has announced $30 million in funding to partner with American businesses to bring products and solutions to market aimed at removing barriers to widespread deployment of solar energy throughout the United States. The funding opportunity announcement (FOA), entitled "SunShot Incubator Program Round 12, SolarMat Program Round 5," is structured to support for-profit entities on the development, testing, and certification of a new product or solution at specific stages of development.
Through the Energy Systems Integration Facility (ESIF), NREL can offer expertise to support FOA proposals like this one. The ESIF is a national user facility available for use by the broader research community. Using ESIF's state-of-the-art equipment and laboratories, NREL's team of scientists and engineers specialize in the areas of:
- Power and module level electronics
- Energy management
- Grid integration, monitoring, and communications
- Utility planning and operations.
The deadline to submit concept papers for the FOA is Dec. 12. Full applications are due Feb. 21, 2017. For more information about the FOA (DOE-FOA-0001640), see the EERE Funding Opportunity Exchange website.
ESIF to Host Fourth International Workshop on Grid Simulator Testing
Save the date for the Fourth International Workshop on Grid Simulator Testing of Energy Systems and Wind Turbine Powertrains, to be held April 25–26, 2017, at the Energy Systems Integration Facility (ESIF).
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Register for Dec. 1 Webinar on Interconnection Rules and Procedures
IEEE is hosting a free one-hour webinar on "Reimagining Interconnection Rules and Procedures for Next-Generation Technologies and Updated Standards" on December 1 at 11:00 a.m. MST. The webinar will feature a presentation from NREL Principal Engineer Michael Coddington. Register now.