Power system transient stability using the critical energy of individual machines

Recent efforts to apply direct methods of transient stability analysis to multi-machine power systems have used the so-called energy functions. These functions describe the system transient energy causing the synchronous generators to depart from the initial equilibrium state, and the power network\u27s ability to absorb this energy so that the synchronous machines may reach a new post-disturbance equilibrium state. In spite of the recent successes it has become increasingly evident that system separation depends not on the total system energy, but rather on the energy of the individual machines or groups of machines tending to separate from the rest. Thus, there is a need for generating transient energy functions for individual machines (or for groups of machines);Using a center of inertia frame of reference, the energy function V(,i) for machine i is derived. V(,i) is composed of kinetic energy and potential energy components. It is shown that the critical value of V(,i) is given by the maximum value of its potential energy component and that this value is fairly constant for any unstable post-fault trajectory. A special computer program has been written to compute the critical value of V(,i) for sustained fault conditions;A procedure for first swing transient stability assessment has been developed using the energy function of individual machines and groups of machines. The method has been tested extensively on two power networks: a 17-generator, 163-bus system which is a reduced version of the network of the state of Iowa; and the IEEE 20-generator, 118-bus system;A theoretical justification for using the critical energy of individual machines in stability assessment is provided using the concept of partial stability. Power system transient stability is analyzed as a partial stability problem with respect to the critical group of machines. It is shown that the transient energy function for the critical group of machines satisfies conditions for partial asymptotic stability

Material modifications due to nonlinear effects created by multiphoton absorption in single crystalline silicon

Material modification inside its bulk via high powered lasers involves much more than just heat transfer and melting of materials. It entails with it complex nonlinear physical phenomena such as multiphoton absorption, self-phase modulation, and self-focussing, amongst many others. These phenomena occur only with ultrafast lasers at very high intensities. Realising subsurface or bulk modifications in semiconductors such as silicon, opens up new avenues in the fields of optoelectronics and optical computation with the potential of increasing current computational speeds by orders of magnitude. The technology of three dimensional volume modification in materials via ultrafast lasers and nonlinear physics, is however, still in its nascent stages. This work explores the possibility of realising bulk modification in silicon and other polymers, and as well as their integration with optoelectronic devices; thus paving way for the future of optical computation

An Algorithmic Approach for Identifying Critical Distance Relays for Transient Stability Studies

After major disturbances, power system behavior is governed by the dynamic characteristics of its assets and protection schemes. Therefore, modeling protection devices is essential for performing accurate stability studies. Modeling all the protection devices in a bulk power system is an intractable task due to the limitations of current stability software, and the difficulty of maintaining and updating the data for thousands of protection devices. One of the critical protection schemes that is not adequately modeled in stability studies is distance relaying. Therefore, this paper proposes an algorithm that uses two methods to identify the critical distance relays to be modeled in stability studies: (i) apparent impedance monitoring, and (ii) the minimum voltage evaluation (MVE). The algorithm is implemented in Python 3.6 and uses the GE positive sequence load flow analysis (PSLF) software for performing stability studies. The performance of the algorithm is evaluated on the Western Electricity Coordinating Council (WECC) system data representing the 2018 summer-peak load. The results of the case studies representing various types of contingencies show that to have an accurate assessment of system behavior, modeling the critical distance relays identified by the algorithm suffices, and there is no need for modeling all the distance relays

Paving the way : a future without inertia is closer than you think

Unless you have been hibernating in a remote cave for the past decade, you will have noticed the explosion of variable renewable generation. Wind power and solar photovoltaics (PVs) have been the subject of dozens of articles, just within the pages of IEEE Power & Energy Magazine. Charts illustrating relentless growth, such as the example from the United States shown in Figure 1 with futures tending toward 100% renewable energy, are common. This figure, provided by the National Renewable Energy Laboratory (NREL), reflects a low-cost, high-renewable projection scenario

Energy System Digitization in the Era of AI: A Three-Layered Approach towards Carbon Neutrality

The transition towards carbon-neutral electricity is one of the biggest game changers in addressing climate change since it addresses the dual challenges of removing carbon emissions from the two largest sectors of emitters: electricity and transportation. The transition to a carbon-neutral electric grid poses significant challenges to conventional paradigms of modern grid planning and operation. Much of the challenge arises from the scale of the decision making and the uncertainty associated with the energy supply and demand. Artificial Intelligence (AI) could potentially have a transformative impact on accelerating the speed and scale of carbon-neutral transition, as many decision making processes in the power grid can be cast as classic, though challenging, machine learning tasks. We point out that to amplify AI's impact on carbon-neutral transition of the electric energy systems, the AI algorithms originally developed for other applications should be tailored in three layers of technology, markets, and policy.Comment: To be published in Patterns (Cell Press

Definition and Classification of Power System Stability – Revisited & Extended

Since the publication of the original paper on power system stability definitions in 2004, the dynamic behavior of power systems has gradually changed due to the increasing penetration of converter interfaced generation technologies, loads, and transmission devices. In recognition of this change, a Task Force was established in 2016 to re-examine and extend, where appropriate, the classic definitions and classifications of the basic stability terms to incorporate the effects of fast-response power electronic devices. This paper based on an IEEE PES report summarizes the major results of the work of the Task Force and presents extended definitions and classification of power system stability.Peer reviewe

The burden of mental disorders, substance use disorders and self-harm among young people in Europe, 1990-2019 : Findings from the Global Burden of Disease Study 2019

Background Mental health is a public health issue for European young people, with great heterogeneity in resource allocation. Representative population-based studies are needed. The Global Burden of Disease (GBD) Study 2019 provides internationally comparable information on trends in the health status of populations and changes in the leading causes of disease burden over time. Methods Prevalence, incidence, Years Lived with Disability (YLDs) and Years of Life Lost (YLLs) from mental disorders (MDs), substance use disorders (SUDs) and self-harm were estimated for young people aged 10-24 years in 31 European countries. Rates per 100,000 population, percentage changes in 1990-2019, 95% Uncertainty Intervals (UIs), and correlations with Sociodemographic Index (SDI), were estimated. Findings In 2019, rates per 100,000 population were 16,983 (95% UI 12,823 - 21,630) for MDs, 3,891 (3,020 4,905) for SUDs, and 89.1 (63.8 - 123.1) for self-harm. In terms of disability, anxiety contributed to 647.3 (432 -912.3) YLDs, while in terms of premature death, self-harm contributed to 319.6 (248.9-412.8) YLLs, per 100,000 population. Over the 30 years studied, YLDs increased in eating disorders (14.9%;9.4-20.1) and drug use disorders (16.9%;8.9-26.3), and decreased in idiopathic developmental intellectual disability (-29.1%;23.8-38.5). YLLs decreased in self-harm (-27.9%;38.3-18.7). Variations were found by sex, age-group and country. The burden of SUDs and self-harm was higher in countries with lower SDI, MDs were associated with SUDs. Interpretation Mental health conditions represent an important burden among young people living in Europe. National policies should strengthen mental health, with a specific focus on young people. Funding The Bill and Melinda Gates Foundation Copyright (C) 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)Peer reviewe