Report on the evaluation of significant EV deployments on distribution feeders, mostly examining their load behavior during voltage sags from the transmission system. A particular emphasis on if a charger is grid-friendly or grid-unfriendly (especially in respect to inducing FIDVR behavior) is examined.

Transmission planners must identify and plan for the potential impacts of widespread EV charging on the reliability of the grid. This paper examines how the addition of significant EV charging loads would affect regions of the grid that are susceptible to fault induced delayed voltage recovery (or FIDVR). We find that EV chargers that cease drawing current at the onset of faults and that delay drawing current until sometime after a fault has cleared will not exacerbate FIDVR and label this behavior grid friendly. We find that EV chargers that do not cease drawing current at the onset of these faults or that resume drawing current immediately after the fault has cleared will exacerbate FIDVR and label this behavior grid unfriendly. We emphasize that modeling and information on EV charging behaviors is currently limited and recommend engagement by the transmission planning community with the EV manufacturing community to improve this situation.

Distribution grid reliability and resilience has become a major topic of concern for utilities and their regulators. In particular, with the increase in severity of extreme events, utilities are considering major investments in distribution grid assets to mitigate the damage of highly impactful outages. Communicating the overall economic and risk-mitigation benefits of these investments to regulators is an important element of the approval process. Today, industry reliability and resilience planning practices are based largely on methods that do not take explicit account of risk. This paper proposes a practical method for identifying optimal combinations of investments in new line segments and storage devices while considering the balance between the risk associated with high impact and low probability (HILP) events and the reliability related to routine failures. We show that this method can be scaled to address large scale networks and demonstrate its benefits using a Target Feeder from the Commonwealth Edison Reliability Program.

Occasionally, forced oscillations (FO) may appear in a power system, and it is critical to quickly identify and isolate their sources in order to prevent damage to other assets. These FOs can interact with natural oscillation modes and propagate to multiple areas, typically managed by different entities, making the source identification problem very challenging. To aid coordination among regional operators during wide-area oscillations, a phasor measurement unit (PMU)-based platform for detecting FOs and identifying their source region was recently tested in the U.S. Eastern Interconnection (EI). Oscillation notifications generated by this platform included an easily-interpretable confidence score that conveyed how imperfect data might have impacted source localization accuracy. This article reports: a) how the confidence score was developed, b) how it performed in an interconnection-level field demonstration, and c) how it can be refined for future implementation. It is shown that the proposed confidence assessment strategy helps system operators ascertain the veracity of source localization results, and accordingly formulate response plans.

manage such changes to ensure reliable operation within the scheduled frequency range. This report presents a systematic approach to identifying metrics that are useful for operating and planning a reliable system with increased amounts of variable renewable generation which builds on existing industry practices for frequency control after unexpected loss of a large amount of generation. The report introduces a set of metrics or tools for measuring the adequacy of frequency response within an interconnection. Based on the concept of the frequency nadir, these metrics take advantage of new information gathering and processing capabilities that system operators are developing for wide-area situational awareness. Primary frequency response is the leading metric that will be used by this report to assess the adequacy of primary frequency control reserves necessary to ensure reliable operation. It measures what is needed to arrest frequency decline (i.e., to establish frequency nadir) at a frequency higher than the highest set point for under-frequency load shedding within an interconnection. These metrics can be used to guide the reliable operation of an interconnection under changing circumstances.

Power industry stakeholders are devoting increasing attention to the risks of long-duration, widespread interruptions (LDWIs) in electricity service. There is concern that these risks are heightening due to more frequent and severe extreme weather events. Numerous studies have examined various aspects of the problem, primarily from an engineering and conceptual perspective. This is the first of two papers reporting the results of a study of LDWIs that focuses on their economic aspects, takes an empirical approach, and includes consideration of institutional factors affecting utilities' efforts to reduce their vulnerabilities to these disruptions. This paper presents background on the problem, including cost concepts relevant to economic valuation of measures to reduce the risks of LDWIs, valuation methods, and the role of the concept of 'resilience' in shaping analysis in this area. This material provides context and motivation for the second paper, which reports on a series of case studies.

Reliable power system operation requires that small-signal stability be maintained at all times. Mode meters are measurement-based tools that provide operators with situational awareness of the system's stability margin. They operate by continually tracking the inter-area modes of oscillation that govern small-signal stability. This paper reports on the deployment of mode meters for online monitoring of two dominant modes of oscillation in the United States' Eastern Interconnection (EI). The use of measurements from system operators across the interconnection to provide continuous tracking is novel in the EI. Results from over four months of analysis reveal diurnal patterns in the modes and demonstrate that they can be tracked through a variety of system conditions. The results from this study continue to build an understanding of the EI's modes that will inform future modeling and monitoring efforts.

This paper summarizes the report prepared by an IEEE PES Task Force.Resilience is a fairly new technical concept for power systems, and it is important to precisely delineate this concept for actual applications.As a critical infrastructure, power systems have to be prepared to survive rare but extreme incidents (natural catastrophes, extreme weather events, physical/cyber-attacks, equipment failure cascades, etc.) to guarantee power supply to the electricity-dependent economy and society.Thus, resilience needs to be integrated into planning and operational assessment to design and operate adequately resilient power systems.Quantification of resilience as a key performance indicator is important, together with costs and reliability.Quantification can analyze existing power systems and identify resilience improvements in future power systems.Given that a 100% resilient system is not economic (or even technically achievable), the degree of resilience should be transparent and comprehensible.Several gaps are identified to indicate further needs for research and development.

LBNL and APPA (the team) jointly examined the extent to which differences in distribution feeder characteristics are correlated with differences in their reliability performance when exposed to three different types of natural hazards (wildlife, weather, and vegetation). The team employed data-driven approaches to quantify the relationships between various measures of feeder reliability and a suite of feeder characteristics individually and jointly via a statistically-based clustering method.

Oscillation monitoring and mitigation are important aspects of reliable bulk power system operation. Forced oscillations, which occur when a piece of equipment injects oscillations into the system, can at times be observed across wide areas, making identification of the source challenging. A phasor measurement unit (PMU)-based wide-area monitoring system capable of identifying the region of the grid containing the source of a forced oscillation was recently deployed for testing in the United State's Eastern Interconnection (EI). The system was designed to operate under real-world constraints, such as PMU data being permanently or temporarily unavailable from some locations. The impact of unavailable data was reflected in a confidence assessment that accompanied oscillation notifications. The metrics used to form this assessment are presented in this paper and validated using thousands of trials from a publicly available test case library of simulated measurements. The results demonstrate that the proposed metrics can help system operators evaluate the veracity of notifications from the source localization system.

This white paper is one of seven being prepared for the Department of Energy (DOE) Microgrid Research & Development (R&D) program as part of a strategy development effort for the next 10 years. The seven white papers focus on the following areas: 1. Program vision, objectives, and R&D targets in 5 and 10 years, 2. T&D co-simulation of microgrid impacts and benefits, 3. Building blocks for microgrids, 4. Microgrids as a building block for the future grid, 5. Advanced microgrid control and protection, 6. Integrated models and tools for microgrid planning, designs, and operations, 7. Enabling regulatory and business models for broad microgrid deployment. This white paper is focused on Topic 7, as a sustainable regulatory and business environment for microgrid development is a foundational element for securing DOE's vision for the future role of microgrids in the U.S. electric sector. The objective of this white paper is to systematically characterize regulatory issues involved in microgrid deployment and microgrid business models, and from this evidence identify a robust and well-justified set of research recommendations for the Department of Energy Office of Electricity, informing programmatic vision, objectives and activities for the DOE Microgrid R&D Program.

Managing the stability of today's electric power systems is based on decades of experience with the physical properties and control responses of large synchronous generators. Today's electric power systems are rapidly transitioning toward having an increasing proportion of generation from nontraditional sources, such as wind and solar (among others), as well as energy storage devices, such as batteries. In addition to the variable nature of many renewable generation sources (because of the weather-driven nature of their fuel supply), these newer sources vary in size—from residential-scale rooftop systems to utility-scale power plants—and they are interconnected throughout the electric grid, both from within the distribution system and directly to the high-voltage transmission system. Most important for our purposes, many of these new resources are connected to the power system through power electronic inverters. Collectively, we refer to these sources as inverter-based resources.

Under existing grid operations, large synchronous generators provide sufficient rotational inertia to form a rigid backbone for the bulk power system. With photovoltaics (PV) forecasted to provide more than 600 GW of generation by 2050 under the U.S. Department of Energy's SunShot Initiative objectives, however, it is clear that power electronic inverters will play a dominant role in future systems, and low-inertia stability must be ensured to maintain system reliability. Today, the risks to system stability can be observed on geographically small islands, such as Hawaii, which contain a relatively large amount of installed PV. These risks stem from a fundamental shortcoming of contemporary control strategies—existing inverter controllers cannot guarantee grid stability. Given that future power systems driven by sustainable resources will be characterized by low inertia, locations such as Hawaii provide a glimpse into the obstacles facing future power systems. Considering these challenges, the aim of this project was to develop and demonstrate distributed inverter controllers that enable the reliable control of low-inertia power systems with hundreds of gigawatts of integrated PV.

The foundation of the United States Department of Energy (DOE) Transmission Reliability research program was established 20 years ago by a series of commissioned white papers. Those white papers described the dramatic institutional and regulatory changes that the U.S. electricity transmission grid was undergoing at the time and articulated the technical challenges that these changes created. The challenges outlined in the white papers were the basis for the initial research goals of the DOE Transmission Reliability program. To a large extent, the reliability research needs outlined in the original white papers have now been met. As a result, now is an appropriate time to step back and review the technical challenges that the industry currently faces and to use those challenges as the basis for identifying the next set of targets for DOE's transmission-related research and development (R&D) programs.

The costs that power interruptions impose on customers and society have emerged as essential considerations for decision-making about power system reliability and resilience. While the direct costs of localized and relatively short-duration power interruptions are well-understood, little is known about the full impact of widespread and long-duration power interruptions, especially the indirect costs and related economy-wide impacts of these events. As a result, the costs of widespread and long-duration power interruptions are generally not or only incompletely considered in utility planning activities. This paper describes a new approach for estimating the economic costs of widespread and long-duration power interruptions. This method involves using survey responses from utility customers to calibrate a regional economic model that can estimate both the direct and indirect costs of these events. Including better estimates of these costs will enhance both the comprehensiveness and completeness of the considerations relied on to support utility planning decisions, especially on grid-hardening strategies and other capital-intensive investments in electricity sector resilience.

There has been a limited amount of peer-reviewed literature on long-term trends in electricity reliability including the underlying factors that impact reliability across the United States. In this analysis, we considered up to 16 years of data from 203 U S. utilities-representing about 70% of electricity sales. Annual frequency of interruptions for an average customer-at the regional and U.S. national-level-has generally decreased over this timeframe. But we do not find that there is a statistically significant trend in the annual duration of interruptions for an average customer. We find that more explicit measures of severe weather are correlated with reliability. We are able to explain 7% and 16% of past variation in the reliability metrics system average interruption duration and frequency indices, respectively, is due to severe weather-a significant improvement over earlier studies. We find that current year spending by utilities is correlated with worse reliability and that cumulative spending over the preceding three years is correlated with better reliability. Finally, we demonstrate that using a statistical instrument to represent the annual frequency of interruptions for an average customer can greatly improve analysis of trends in the annual duration of interruptions for an average customer. Published by Elsevier Ltd.

Author(s): Sanstad, Alan H; Zhu, Qianru; Leibowicz, Benjamin; Larsen, Peter H; Eto, Joseph H | Abstract: The risks of long-duration, widespread interruptions (LDWIs) in electrical power are a concern of U.S. regulators, the electric power industry, and stakeholders. Those responsible for making decisions about increasingly costly investments to prevent such interruptions and to facilitate rapid recovery when they do occur need relevant information on which to base those decisions. Although a number of studies have examined the physical and engineering impacts of extreme weather and other precipitating events on the bulk power system, decision makers evaluating investments in preventive strategies need information on the costs of past power interruptions and the benefits of preventing them in the future. This paper contributes to addressing this need by offering six case studies that detail the economics, at the level of the utility service territory, of power interruptions caused by extreme weather and lasting from a few days to several weeks. These intermediate-duration interruptions have been, and will continue to be, the most common type of major electric power disruption. They are longer than the short-term disruptions addressed in utility reliability planning, but not as long or widespread geographically as the national-scale interruptions with durations of many weeks, months, or longer that have been examined in some recent studies. Through case studies, we are able to address the following five questions that have important policy and long-term planning implications for reducing power system vulnerabilities: 1. How do utilities assess the costs of system damage caused by extreme weather and the costs of recovering from this damage? 2. How do utilities estimate customer costs of past power interruptions? 3. How do utilities or others estimate the costs and benefits of investments to reduce power system vulnerabilities to future extreme weather events? 4. How do utilities and regulators use the concept of resilience in economic assessments of extreme weather impacts and the value of preventive investments? 5. How do regulatory processes influence utilities’ economic analysis related to power interruptions? Finally, the case studies reveal a number of areas in which further research could be beneficial to utilities and regulators dealing with risks associated with LDWIs.

This research roadmap is intended to fill the knowledge gap by providing a system view of grid-forming inverter-based resource controls and their impact on grid stability, which we believe is central to meeting some of the challenges to operating the future North American electric power system. This includes the roles and requirements of grid-forming inverter-based resources—including solar photovoltaics, wind generators, and energy storage. For this roadmap, we focus on a specific family of grid-forming inverter control approaches that do not rely on an external voltage source (i.e., no phase-locked loop) and that can share load without explicit communications. Although the roadmap is focused narrowly on system challenges for grid-forming controls and power system stability, including interactions with protection, we hope it serves as a foundational element for future system-of-systems roadmapping needed in a broader grid modernization effort with increasing deployments of inverter-based resources. The roadmap first introduces formal definitions for the grid stability topics and then describes the differences between grid-forming and traditional grid-following control approaches for inverter-based resources. The core of the roadmap consists of a review of current research and an outline of research needs related to five grid-forming inverter topics: frequency control, voltage control, system protection, fault ride-through and voltage recovery, and modeling and simulation. The review both delineates contemporary advances and highlights open research questions that must be addressed to enable the widespread adoption of inverter-based resources across the grid. Feedback from industry on these research questions is incorporated, including discussions during the Workshop on Grid-forming Inverters for Low-inertia Power Systems. The workshop included industry presentations and discussion of ongoing research, technology gaps, and piloting needs. This roadmap concludes by offering a multiyear perspective on the gradual field validation of grid-forming inverters. This perspective recognizes that the scale and scope of the types of power systems that inverters will be called on to provide grid-forming services will and should begin modestly. Specifically, this roadmap recognizes that inverter controls today are predominantly grid-following and that future power systems will involve a mix of inverter-based resources with both grid-following and grid-forming control capabilities. Growth over time will depend on how well grid-forming inverters perform and what advantages they bring as penetration levels (instantaneous and average) of inverter-based resources increases. This recognition, in turn, establishes a natural sequence of priorities for the research questions that must be addressed. Following this multiyear perspective, the roadmap offers short descriptions of two specific near-term research priorities: the review of regulatory and technical standards and the development of advanced modeling techniques. These priorities are foundational. We recommend immediate pursuit of them in parallel with and in direct support of the research outlined by our multiyear perspective.

Author(s): Faris, Anthony; Kosterev, Dmitry; Eto, Joseph H; Chassin, Dave | Abstract: In 2015, NERC’s reliability standards were revised to require the use of dynamic load models in transmission planning studies. To comply with the standards, planners must use load models that explicitly represent the dynamic behavior of the different constituents of load at each load bus within their transmission planning models. The most important of these constituents are motor-driven and power electronics-based loads. Collectively, these representations are known as composite load models. In anticipation of the compliance date for the new standards, NERC’s Load Modeling Task Force (LMTF), in 2019, initiated a field test of composite load models involving the regional reliability planning entities. In support of the field test, DOE and BPA researchers developed region-specific composite load models that could be assigned to each non-industrial load bus in the planning models for each of the North American interconnections. Separate models were developed for each hour of a summer peak day, a winter peak day, and a spring light-load day. This report is the technical documentation for the load composition analysis that was conducted to develop these non-industrial composite load models.