Benjamin Kroposki

National Renewable Energy Laboratory | NREL · Power Systems Engineering Center

This article is a reprint from B. Kroposki et al., "Autonomous Energy Grids: Controlling the Future Grid With Large Amounts of Distributed Energy Resources," in IEEE Power and Energy Magazine, vol. 18, no. 6, pp. 37-46, Nov.-Dec. 2020, doi: 10.1109/MPE.2020.3014540. Please access the original article on IEEE Xplore.

This paper outlines a suite of energy-management problems for inverter-based power networks from the vantage point of optimal control and (non)linear optimization. The problems are categorized based on timescales dictated by the network dynamics, and organized methodologically based on the problem complexity. A growing body of literature has addres...

Understanding the technical and economic challenges of achieving 100% renewable energy (RE) electric power systems is critical, given the increasing number of United States regional and state commitments toward this goal. Although no detailed study of a major utility of large interconnection under 100% RE system has been published, considerable lit...

As many island power systems seek to integrate high levels of renewable energy, they face new challenges on top of the existing difficulties of operating an isolated grid. With their drastically declining cost, variable renewables, such as wind and photovoltaics (PVs), are increasingly being integrated into island grids to reduce the use of importe...

As many island power systems seek to integrate high levels of renewable energy, they face new challenges on top of the existing difficulties of operating an isolated grid. With their drastically declining cost, variable renewables, such as wind and photovoltaics (PVs), are increasingly being integrated into island grids to reduce the use of importe...

As the penetration of distributed energy resources based on renewable sources increases, several technical challenges are introduced into energy grids. These include real-time power balance, control of bi-directional energy flow, power quality, distributed optimization, state estimation and topology estimation in distribution grids, and multi-level...

Distributed energy resources (DERs)-which can include solar photovoltaic (PV), fuel cells, microturbines, gensets, distributed energy storage (e.g., batteries and ice storage), and new loads [e.g., electric vehicles (EVs), LED lighting, smart appliances, and electric heat pumps]-are being added to electric grids and causing bidirectional power flow...

Test systems are important tools and benchmark for power system research. Currently, there is a lack of standard test systems for modern transmission expansion planning (TEP) research, especially under high variable renewable energy (VRE) penetrations. This article describes a 38-bus test system named the HRP-38 system dedicated to TEP. “HRP” stand...

Rapidly increasing levels of variable inverter‐based renewable energy sources are quickly changing electric power systems and prompting questions about how the systems will be operated when renewable generation becomes the dominant technologies. In this article, we review the status of this shifting paradigm in power systems throughout the world. W...

As power systems across the globe continue to achieve higher instantaneous penetrations of power electronic converter-interfaced renewable sources, the stability of these power systems is challenged because of the removal of synchronous machines, from which stability is traditionally derived. Although technological solutions to these stability chal...

Purpose of Review This paper highlights the main impacts of transportation and building electrification on electricity grid infrastructure, operations, and planning. We focus on which electric technologies are expected to grow, how electrification will impact electricity demand and grid activities, and which solutions might improve the integration...

The digitization of smart grid distributed generation and industrial control systems has prompted utilities to deploy tools with ubiquitous communications that potentially widen the attack surface. The utilities still continue to rely on the traditional cybersecurity technologies, such as firewalls, anti-malware tools, and passwords that do not ens...

Solar energy has the potential to play a central role in the future global energy system because of the scale of the solar resource, its predictability, and its ubiquitous nature. Global installed solar photovoltaic (PV) capacity exceeded 500 GW at the end of 2018, and an estimated additional 500 GW of PV capacity is projected to be installed by 20...

The integration of variable renewable energy (VRE) generation, i.e. wind power and solar photovoltaic, brings significant uncertainty for the power system operation. Different with VRE techniques, concentrating solar power (CSP) is an appealing renewable generation technology due to its dispatch-ability through the use of thermal energy storage (TE...

Concentrating solar power (CSP) plants are able to provide both renewable energy and operational flexibility at the same time due to its thermal energy storage (TES). It is ideal generation to power systems lacking in flexibility to accommodate variable renewable energy (VRE) generation such as wind power and photovoltaics. However, its investment...

Achieving high renewable energy penetrated power systems requires considerable operational flexibility to hedge the variability and uncertainty of variable renewable energy (VRE) generation. Compared with VRE sources, concentrating solar power (CSP) is an emerging controllable renewable generation technique that utilizes solar thermal power to gene...

Current frameworks to monitor, control, and optimize large-scale energy systems are becoming increasingly inadequate because of significantly high penetration levels of variable generation and distributed energy resources being integrated into electric power systems; the deluge of data from pervasive metering of energy grids; and a variety of new m...

As more variable renewable energy (VRE) such as wind and solar are integrated into electric power systems, technical challenges arise from the need to maintain the balance between load and generation at all timescales. This paper examines the challenges with integrating ultra-high levels of VRE into electric power system, reviews a range of solutio...

Coordinating technology, policy, and business innovations

What does it mean to achieve a 100% renewable grid? Several countries already meet or come close to achieving this goal. Iceland, for example, supplies 100% of its electricity needs with either geothermal or hydropower. Other countries that have electric grids with high fractions of renewables based on hydropower include Norway (97%), Costa Rica (9...

The articles in this special section focus on energy systems integration (ESI). Electric power systems around the world are experiencing great changes, including the retirement of coal and nuclear plants along with a rapid increase in the use of natural gas turbines and variable renewable technologies such as wind and solar. There is also much more...

When Steve Johnson had solar panels installed on the roof of his Boulder, Colo., home several years ago, he considered it his personal contribution to making the world a little cleaner. And if his grid-connected photovoltaic (PV) system would occasionally cause his electricity meter to spin backward during the day and trim his utility bills, so muc...

This presentation provides a high-level overview of unintentional islanding in power systems with distributed resources

Energy Systems Integration (ESI) is the process of coordinating the operation and planning of energy systems across multiple pathways and/or geographical scales to deliver reliable, cost- effective energy services with minimal impact on the environment.It is imperative that stakeholders gain a better understanding of what ESI is and how we can use...

Distributed control strategies applied to power distribution control problems are meant to offer robust and scalable integration of distributed energy resources. However, the term "distributed control" is often loosely applied to a variety of very different control strategies. This leads to problems in the design phase as well as with the performan...

With the rapidly increasing penetration of wind power, wind producers are becoming increasingly responsible for the deviation of the wind power output from the forecast. Such uncertainty results in revenue losses to the wind power producers (WPPs) due to penalties in ex-post imbalance settlements. This paper explores the opportunities available for...

Discusses energy storage options for the power grid in the future.

This issue of IEEE Power & Energy Magazine is the fourth in a series that addresses issues with integrating solar energy into the electric grid. Starting in this issue and expanding in future issues, we will investigate the integration of all distributed energy resources, not just solar-based distributed energy resources, with electric power system...

The current status of international microgrid research, development, and demonstration (RD&D) was on display and open for review and debate in Tianjin, China, 13?14 ?November 2014 at the Tianjin 2014 Symposium on Microgrids. Sponsored by the U.S. Department of Energy Office of Electricity Delivery and Energy Reliability (U.S. DOE-OE) and the Energy...

This article describes the advanced functions and control modes currently being implemented in DER power converters. It presents the facilities and features of new test labs that have recently been built in Europe as well as the United States to facilitate the testing and certification of new DERs with advanced grid support functions. Case studies...

To successfully operate and deliver its promise of a seamlessly integrated buildings-grid infrastructure, a transactive energy ecosystem requires new approaches to planning and operating the power grid. These approaches include technological advances in the area of standards, measurements, control strategy, and theories so that the essential transa...

To successfully operate and deliver its promise of a seamlessly integrated buildings-grid infrastructure, a transactive energy ecosystem requires new approaches to planning and operating the power grid. These approaches include technological advances in the area of standards, measurements, control strategy, and theories so that the essential transa...

To successfully operate and deliver its promise of a seamlessly integrated buildings-grid infrastructure, a transactive energy ecosystem requires new approaches to planning and operating the power grid. These approaches include technological advances in the area of standards, measurements, control strategy, and theories so that the essential transa...

Climate change concerns mandated renewable portfolio standards, lucrative government incentives, and accelerated cost reduction in renewables, and distributed energy applications are driving steep growth in system installations. Distributed energy resources (DERs) are not commonly connected to a bulk power transmission system but are interconnected...

The articles in this special section focus on energy systems integration (ESI) which enables the effective analysis, design,and control of these interactions and interdependencies along technical, economic, regulatory, and social dimensions.

A special section in this issue of IEEE Transactions on Sustainable Energy (TSTE) is devoted to Solar Energy. This section of TSTE highlights some of the most recent research that addresses these integration challenges and presents novel solutions for the integration of solar energy into the electric power system. The Special Section in this issue...

This paper presents simulation results for a taxonomy of typical distribution feeders with various levels of photovoltaic (PV) penetration. For each of the 16 feeders simulated, the maximum PV penetration that did not result in a steady-state voltage or current violation is presented for several PV location scenarios: clustered near the feeder sour...

The world's energy paradigm continues to undergo a rapid shift towards an increased use of renewable energy sources. To support this shift, an advanced electric power system architecture is being implemented by many electric utilities, interconnected with new distributed energy resources. As these new installations occur, it is essential to verify...

The articles in this special issue focus on solar power generation, including new technologies, services, and applications.

The installed capacity of photovoltaic systems has recently increased at a much faster rate than the development of grid codes to effectively and efficiently manage high penetrations of PV within the distribution system. In a number of countries, PV penetrations in some regions are now raising growing concerns regarding integration. Management stra...

Energy systems integration (ESI) enables the effective analysis, design, and control of these interactions and interdependencies along technical, economic, regulatory, and social dimensions. By focusing on the optimization of energy from all systems, across all pathways, and at all scales, we can better understand and make use of the co-benefits th...

A methodology is proposed and executed to characterize and model inverters for grid integration studies using Power Hardware-in-the-Loop. A Hardware-in-the-Loop system is configured using a Real-Time Data System (RTDS), grid simulator, load bank, photovoltaic inverter, DC power supply and bus system. A characterization scheme is developed on the RT...

Solar photovoltaics (PV) is the dominant type of distributed generation (DG) technology interconnected to electric distribution systems in the United States, and deployment of PV systems continues to increase rapidly. Considering the rapid growth and widespread deployment of PV systems in United States electric distribution grids, it is important t...

The world is highly dependent on an energy infrastructure that produces electricity and fuels; delivering these to customers for a wide variety of end-use applications. There is a renewed push to integrate larger quantities of variable renewable generation, advanced energy storage, and smart communications and controls to allow for increased use of...

Bidirectional power electronics can add vehicle-to-grid (V2G) capability in a plug-in vehicle, which then allows the vehicle to operate as a distributed resource (DR). The uniqueness of the battery-based V2G power electronics requires a test procedure that will not only maintain IEEE interconnection standards, but can also evaluate the electrical p...

With the development of smart grids and the deployment of their enabling technologies, improved data acquisition will be needed at the distribution level to understand the full impact of these changes. With this in mind, NREL has developed a high-speed measurement and data collection network targeted specifically at the distribution level. This net...

With the publication of IEEE 1574.4 Guide for Design, Operation, and Integration of Distributed Resource Island Systems with Electric Power Systems, there is an increasing amount of attention on not only the design and operations of microgrids, but also on the proper operation and testing of these systems. This standard provides alternative approac...

The Hawaii Clean Energy Initiative (HCEI) is working with a team led by the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory (NREL) and Sandia National Laboratory (Sandia) to assess the economic and technical feasibility of increasing the contribution of renewable energy sources on the island of Lanai with a stated goal of rea...

This white paper evaluates the origins and usefulness of the capacity penetration screen, offer short-term solutions which could effectively allow fast-track interconnection to many PV system applications, and considers longer-term solutions for increasing PV deployment levels in a safe and reliable manner while reducing or eliminating the emphasis...

As deployment rates for new energy technologies rapidly increase, there is growing emphasis on infrastructure and systems operations upgrades that will be needed to accommodate the unique operating characteristics of new renewable, efficiency, and end-use technologies. To meet these integration challenges, the National Renewable Energy Laboratory (...

In 2008, a 300 kWpeak photovoltaic (PV) system was installed on the rooftop of the Colorado Convention Center (CCC). The installation was unique for the electric utility, Xcel Energy, as it had not previously permitted a PV system to be interconnected on a building served by the local secondary network distribution system (network). The PV system w...

Photovoltaic (PV) system capacity penetration, or simply 'penetration,' is often defined as the rated power output of the aggregate PV systems on a distribution circuit segment divided by the peak load of that circuit segment. Industry experts agree that a single value defining high penetration is not universally applicable. However, it is generall...

A significant increase in photovoltaic (PV) system installations is expected to come on line in the near future and as the penetration level of PV increases, the effect of PV may no longer be considered minimal. One of the most important attributions of additional PV is what effect this may have on protection systems. Protection engineers design pr...

The U.S. Department of Energy's National Renewable Energy Laboratory, Sandia National Laboratories, the Solar Electric Power Association, the Utility Wind Integration Group, and the U.S. Department of Energy hosted a day-long public workshop on the variability of photovoltaic (PV) plants. The workshop brought together utilities, PV system developer...

The last two years have seen a tremendous increase in the number of installed solar energy systems. In 2010, annual grid-connected photovoltaic (PV) installations in the United States and worldwide were expected to be about 0.8 GW and 16–18 GW, respectively. At the end of 2010, the cumulative installed base of grid-connected PVs in the United State...

The objective of this report is to provide a test plan for V2G testing. The test plan is designed to test and evaluate the vehicle's power electronics capability to provide power to the grid, and to evaluate the vehicle's ability to connect and disconnect from the utility according to a subset of the IEEE Std. 1547 tests.

With the increasing use of distributed energy (DE) systems in industry and its technological advancement, it is becoming more important to understand the integration of these systems with the electric power systems. New markets and benefits for DE applications include the ability to provide ancillary services, improve energy efficiency, enhance pow...

New York City has set a goal to increase its installed photovoltaic (PV) capacity from 1.1 MW in 2005 to 8.1 MW by 2015. A key barrier to reaching this goal, however, is the complexity of the interconnection process on secondary network distribution systems (network). Although most areas of the country use simpler radial distribution systems to dis...

High-penetration photovoltaic (PV) system deployment is becoming a reality in several regions of the United States and the trend toward high penetration levels will continue to rise due to decreasing PV system costs in concert with increasing electric utility rates and societal deliberations. New standards and codes for high-penetration PV deployme...

The National Renewable Energy Laboratory (NREL) conducts a variety of research in the area of hybrid power system integration and microgrids. NREL is studying hybrid (stand-alone) power systems incorporating photovoltaic power in the United States and assessing the characteristics and status of government-installed hybrid systems greater than 2 kW...

There is an increasing demand both by legislation and the public for a more secured, reliable and efficient power system using dispatchable and non-dispatchable renewable resources. However, the existing design and operational practice of the electrical power grid does not lend itself easily to the incorporation of non-dispatchable renewable energy...

This paper describes a method for estimating the technical potential of rooftop photovoltaics (PV) using the National Renewable Energy Laboratory's (NREL) In My Backyard (IMBY) tool. This method is applied to 10 utility network areas in New York City to estimate PV yield potential. PV power generation is compared to network loads to determine when...

Due to increased attention towards clean and sustainable energy, distributed energy (DE) systems are gaining popularity all over the world. Power electronics are an integral part of these energy systems being able to convert generated electricity into consumer usable and utility compatible forms. But the addition of power electronics adds costs to...

This paper discusses studies funded by the National Renewable Energy Laboratory (NREL) via SunPower, Inc. and the California Energy Commission (CEC), performed by New Power Technologies and Optimal Technologies that showed that high-penetrations of distribution-connected storage devices or plug-in vehicles can have adverse grid impacts due to their...

Climate change concerns, mandatory requirements for the renewable portfolio standards, incentives offered by the Government, and cost reduction in renewables and distributed energy sources (DER) are some of the driving forces for the steep growth in DER installations. DERs are commonly connected near the load in the electric power distribution syst...

Microgrids are intentional islands formed at a facility or in an electrical distribution system that contain at least one distributed energy resource and associated loads. One of the most challenging aspects in the commercial deployment of microgrids is the ability to test and evaluate various microgrid technologies and system to evaluate their eff...

Wind, solar, and other renewable energy important part of any present-day energy the portion of energy they supply to the certainly be increasing over the next few Arguably, large-scale wind power has reached technological maturity, and with more than 100 GW of capacity ample experience exists on integrating wind systems. Solar technologies, on the...

As deployment rates for new energy technologies rapidly increase, there is growing emphasis on infrastructure and systems operations upgrades that will be needed to accommodate the unique operating characteristics of new renewable, efficiency, and end-use technologies. To meet these integration challenges, the National Renewable Energy Laboratory (...

While the number of PV systems interconnected to the electric grid has increased significantly over the last decade, only recently have PV systems been installed in major metropolitan areas and tied to electric distribution secondary network systems (networks). This paper examines six cases studies of photovoltaic (PV) systems integrated into secon...

Climate change concerns, mandated renewable portfolio standards, lucrative government incentives, and accelerated cost reduction in renewables and distributed energy applications are driving steep growth in system installations. distributed energy resources (DER) are not commonly connected to a bulk power transmission system, instead are interconne...

The six articles in this special issue focus on solar energy integration and examine some of the issues associated with the large-scale deployment of solar energy.

Now is the time to plan for the integration of significant quantities of solar energy into the electricity grid. Although solar energy constitutes a very small portion of our energy system today, the size of the resource is enormous: The earth receives more energy from the sun in one hour than the global population uses in an entire year. In additi...

Data and analysis are needed to understand the variability of photovoltaic (PV) plants to avoid unnecessary barriers to the interconnection of PV. Several datasets show clouds can cause rapid changes in solar insolation. Smoothing of rapid ramps, however, occurs within PV plants. The degree of smoothing depends on plant size. Smoothing occurs on ev...