Self-healing power systems offer significant resilience benefits. Most existing self-healing concepts depend on high-speed communications for data sharing, which can be cost-prohibitive or unreliable during emergency events. Greater benefit could be achieved if the system could autonomously identify the relative locations of the line relays. Using lower-bandwidth and less expensive communication methods. This paper presents and analyzes an approach using a radio-frequency pulse transmitted over the neutral line of a microgrid to enable line relays to automatically determine their electrical relationships and enhance self-healing capability.

Energy security is a pressing global concern, as nations dependent on electric grids and critical infrastructure face vulnerabilities from various threats, including electromagnetic pulse, cyber-physical attacks, kinetic attacks, and increasingly frequent natural disasters. For the U.S. and its allies, these threats represent significant security risks, as compromised infrastructures can undermine essential mission functions. Securing these systems is a top priority, and the international community acknowledges the need for cross-border cooperation and partnerships. In response, Sandia National Laboratories has initiated a Mission Campaign focused on Resilient Energy Systems, aimed at advancing innovative science and technology to enhance energy security and the resilience of critical infrastructure. While the campaign primarily targets U.S. energy systems, its research outcomes are applicable globally and align with NATO’s energy security objectives. This chapter provides an overview of the Mission Campaign’s three research thrusts: (1) Science of Vulnerabilities, which develops tools to assess risks and vulnerabilities; (2) Materials, Device, and Cyber Innovation, which seeks new high-energy materials and cost-effective solutions for physical and cyber threats; and (3) System-Level Threat-Informed Computational Science, which analyzes critical elements of the electrical energy system to create a more resilient architecture. The chapter also describes an integrated portfolio of research across four applied areas: a cyber vulnerabilities toolset, resilience measurement and optimization, solid-state transformers, and Electromagnetic Pulse mitigation. Finally, the chapter highlights specific projects and tools under development, and outlines plans for translating research into real-world applications.

The integration of distributed energy resources (DERs), particularly photovoltaic (PV) systems, presents new challenges in maintaining the stability and reliability of electrical grids. Unintentional islanding, where DERs continue to energize part of the grid even after disconnection, poses safety risks, disrupts power quality, and complicates protection protocols. This study focuses on developing a comprehensive numerical model to analyze and address unintentional islanding events in grid-connected PV inverters when an extensive high-voltage transmission line introduces significant capacitive effects. The model includes a PV inverter, an induction motor load, and a high-voltage transmission line. One of the key objectives of this work is to simulate highly capacitive conditions that are susceptible to sustaining islanding. An optimization algorithm is used to tune the transmission line capacitance such that the net active and reactive power flow to the grid is minimized, creating worst-case detection conditions. The island detection time is evaluated by testing the system under various configurations and operating points. The parameters varied in the model include transmission line length and motor load level, expressed as a percentage of the rated motor capacity. This paper also studies the influence of having aggregated and disaggregated motor loads connected to the system. The results demonstrate that certain combinations of line capacitance and motor loading, particularly at intermediate load levels, can significantly delay islanding detection, exceeding 300 seconds in some cases, thus challenging conventional anti-islanding techniques. Insights gained from this study contribute to the development of more robust islanding detection strategies for PV inverters, particularly in scenarios with high DER penetration and weak grid conditions. This work provides a modeling framework to support the reliable integration of renewable energy sources into existing power systems.

Fault location, isolation, and service restoration of a self-healing, self-assembling microgrid operating off-grid from distributed inverter-based resources (IBRs) can be a unique challenge because of the fault current limitations and uncertainties regarding which sources are operational at any given time. The situation can become even more challenging if data sharing between the various microgrid controllers, relays, and sources is not available. This paper presents an innovative robust partitioning approach, which is used as part of a larger self-assembling microgrid concept utilizing local measurements only. This robust partitioning approach splits a microgrid into sub-microgrids to isolate the fault to just one of the sub-microgrids, allowing the others to continue normal operation. A case study is implemented in the IEEE 123-bus distribution test system in Simulink to show the effectiveness of this approach. The results indicate that including the robust partitions leads to less loss of load and shorter overall restoration times.

This paper proposes a direct transfer trip (DTT) scheme for the protection of low voltage (LV) secondary spot networks. The conventional protection on secondary networks is based on network protector units (NPU). NPUs play a critical role in the effective isolation of faults by disconnecting the secondary side of service transformers and avoiding the flow of fault currents through alternative paths in LV spot networks. The proposed approach improves the performance of conventional NPU logic and addresses two major challenges. It is shown that the proposed approach can effectively isolate ground faults on the primary system for which the conventional NPUs can fail to detect when the service transformer has a Delta winding on the high voltage side. Moreover, the proposed approach can allow for the reverse power flow caused by the Distributed Energy Resources located in the secondary LV networks. The performance of the proposed approach is validated using a hardware-in-the-loop testbed that runs a LV spot network in Opal-RT real-time digital simulator.

Under frequency load shedding (UFLS) schemes are the last resort protection mechanism in order to avoid the collapse of a power system upon a sudden large loss of generation. These schemes disconnect load if the frequency decline exceeds a pre-established threshold. Although existing multi-stage UFLS schemes are not considered an optimal solution, they are widely deployed in practice for their simplicity and reliability. Typically, UFLS operators exclude critical facilities from shedding, while the remaining load is divided among the UFLS stages in an arbitrary way. This current approach does not take into account load sensitivity to outages. In this paper, the concept of a multistage criticality-informed UFLS scheme is introduced to demonstrate the benefits of including high-granularity criticality data in the load assignment process. Employed criticality functions can potentially include social, economic, and demographic data, which are more detailed than the blunt aggregation of loads based on types. In addition, the developed methodology supports time-dependent criticality functions, which are taken into account in the load assignment process. This approach is valid for existing traditional power systems structures, without the need for additional resources. The proposed concept is verified with the Quebec 29-bus system in a MATLAB/Simulink testbed. The results show that the proposed approach effectively constrains the criticality of loads shed across the system.

The increasing frequency and severity of extreme weather events underscore the need to bolster energy infrastructure resilience in remote coastal communities exposed to climate hazards. In recent years, considerable effort has been made to harden the grid infrastructure of remote communities through investment in energy storage, advanced metering, renewable generation and energy-efficiency upgrades. However, simulation-based studies are still needed to identify appropriate locations for investment and determine the adequacy of existing infrastructure in supporting new resources. Preparing the required models shares challenges common to many utilities; e.g., limited metering, disparate data sources, and over-extended workforces. This paper describes modeling efforts undertaken to represent, within a unified co-simulation platform: (a) the electric distribution network and (b) the energy dynamics of a community medical center, in the remote community of Cordova, Alaska. With the help of case-studies, it is shown how the developed simulation platform can help the local utility in making decisions regarding capital investment aimed at enhancing community resilience.

Self-Healing Power Systems (SHePS) have potential to greatly improve electric power system resiliency. Many SHePS concepts rely on high-speed networked communications, which increase costs and can limit self-assembly capability. Thus, SHePS concepts that rely only on local measurements can play an important role. One key challenge in SHePS using only local measurements is in detecting and mitigating thermal overloads of conductors without shedding all loads on the overloaded conductor. This paper proposes a new thermal overload mitigation technique, referred to as the “tapping” method, that involves patterned switching of line relays to modulate the voltage and recognition of that switching pattern by downstream load-control relays, which then disconnect minimum-priority loads to relieve the overload. The loads can be automatically reconnected after a set of criteria is met, again using only local measurements. The technique is described in detail and demonstrated in PSCAD simulation.

We consider the problem of adaptive load shedding in power systems experiencing sudden frequency variations due to imbalances in power generation and load consumption. While existing research has primarily focused on load-shedding schemes using voltage-stability indices or predefined weighting factors, our approach integrates a new type of criticality function. These functions consider diverse shedding priorities across the system’s loads, incorporating both technical and societal data. This inclusion allows the decision-making algorithms used by the load-shedding scheme to incorporate demographic and technical information, mitigating unintended second-order adversarial effects within system subsets. Our proposed methodology represents an initial step towards systematically incorporating societal factors into power system load shedding schemes. We present numerical simulations that demonstrate the efficacy of the proposed under-frequency load-shedding scheme in achieving an equitable rearrangement of the shed load without compromising the scheme’s effectiveness.

This document is a summary of a report prepared by the IEEE PES Task Force (TF) on Microgrid (MG) Dynamic Modeling, IEEE Power and Energy Society, Tech. Rep. PES-TR106, 2023. In this paper, the major issues and challenges in microgrid modeling for stability analysis are discussed, and a review of state-of-the-art modeling approaches and trends is presented. In the context of the IEEE 1547 standard, the document covers issues associated with component models for MG dynamic studies and simulations, including generator and grid modeling, full and average converter models, unbalanced and balanced system conditions, dynamic and static loads, protection requirements, and detailed and simplified controls considering communications delays, packet losses, and security issues. Considering the future integration of grids and MGs to form broad integrated networks, a discussion is presented of the use of phasor vis-à-vis electromagnetic transient simulation tools for MG dynamic stability studies, as well as modeling scale-up issues and MG equivalent models. Specifically white-, grey-, and black-box models, are presented. This TF paper and companion report constitute a modeling guide for R&D groups working on developments and standards of MGs with a focus on stability issues.

In power systems, Single-Line-to-Ground (SLG) faults are the most common type of fault. When a three-phase four-wire system supplied by an ungrounded synchronous generator is subjected to SLG faults, the unfaulted phases are expected to exhibit significant ground-fault over-voltage (GFOV). Mitigation of this is via effective grounding, as described in IEEE Std 62.92.2. However, for inverter-based resources (IBRs), the physical mechanism that leads to GFOV in synchronous machines is not present. This paper investigates whether GFOV is a problem in IBRs, and whether conventional mitigation requirements, such as providing a grounding transformer (GTF), are suitable for IBR installations. To answer these questions, a Controller Hardware-in-the-Loop (CHIL) based performance analysis is conducted. To this end, different simulation models have been developed to analyze the IBRs control and protection response. The models are comprised of a 13.2 kV, 500 kW distribution system fed by a grid connected PV inverter which was simulated in Typhoon HIL 604 real time simulator, with a IEEE Std 1547-2018 compliant external physical controller connected in the loop. The experimental set-up and tests conducted are explained and results are analyzed, showing that effective grounding requirements are much different than those for traditional generators.

Due to their increased levels of reliability, meshed low-voltage (LV) grid and spot networks are common topologies for supplying power to dense urban areas and critical customers. Protection schemes for LV networks often use highly sensitive reverse current trip settings to detect faults in the medium-voltage system. As a result, interconnecting even low levels of distributed energy resources (DERs) can impact the reliability of the protection system and cause nuisance tripping. This work analyzes the possibility of modifying the reverse current relay trip settings to increase the DER hosting capacity of LV networks without impacting fault detection performance. The results suggest that adjusting relay settings can significantly increase DER hosting capacity on LV networks without adverse effects, and that existing guidance on connecting DERs to secondary networks, such as that contained in IEEE Std 1547–2018, could potentially be modified to allow higher DER deployment levels.

The growing distributed energy resources (DER) penetration in the low-voltage network (600V and below) challenges the existing protection philosophy and practice. To assess the impact of high DER penetration, the authors built a representative low-voltage network model in real-time electromagnetic transient software and performed hardware-in-the-loop (HIL) protection studies. In the first stage of the effort, the authors invited four major U.S. utilities with low-voltage networks to a technical workshop to survey the modeling and study needs. Guided by the workshop discussions, the authors developed various real-time simulation models, including a low-voltage network model, a model of a commonly used network protector relay, and DER models. Finally, the authors conducted hardware-in-the-loop protection studies to investigate and mitigate the high DER penetration impacts. Part 1 of the paper summarizes the technical workshop outcomes and low-voltage network modeling approaches. Part 2 of the paper reports the HIL simulation setup, high DER penetration impact assessment, and benchmark results of a promising mitigation solution.