Inertia Energy Research Articles

Comparative analysis and optimal allocation of virtual inertia from grid‐forming and grid‐following controlled ESSs

AbstractA broad consensus of neutralizing the carbon dioxide emissions facilitates the transition to the renewable energy power system. Meanwhile, the concerns about the volatility of renewable energies are growing as the rotational inertia of power system becomes inadequate. To maintain the frequency stability of power system, some studies for configuring inertia energy storage systems (ESSs) are carried out, mainly focusing on the allocation of virtual inertia from grid‐forming ESS. In contrast, the allocation of virtual inertia from grid‐following ESS has not been well elaborated and the differences in virtual inertia provided by these two modes are yet to be revealed. Based on ‐norm and Kron reduction, firstly, the state‐space model of post‐disturbance system is established, together with the transient performance evaluation. Then the inertia characteristics of both grid‐forming and grid‐following devices are formulated, followed by the unified gradient descent optimization method for allocating virtual inertia. A modified IEEE 39‐bus system and its time‐domain simulations help in the verification of the contribution of this paper. Through the comparative analysis of corresponding optimal results, the conclusions from two aspects are drawn: in terms of transient frequency support, the grid‐forming devices can provide no less than better inertia support; with the higher power capacity and similar energy capacity, the grid‐forming devices can relieve the response pressure of other generators by approximately .

Cohesive phase-field model for dynamic fractures in coal seams

A novel rate-dependent cohesive phase-field model that can simulate fluid-driven dynamic quasibrittle fracture in soft coal rocks is presented. The coal matrix and fractures are described by a unified fluid continuity equation, and the Poiseuille flow in the fractures is modeled by deformation-dependent permeability. Dynamic evolution equations for porosity, permeability and the Biot coefficient during phase-field evolution are developed. The phase-field evolution equation is derived from the total energy generalization based on the Francfort–Marigo variational principle. To simulate the rate-dependent dynamic fracture problem accurately, the effects of the phase-field evolution dissipation energy and inertia energy are considered. The above multifield coupled system is solved via a staggered approach within the finite element framework via the Newton–Raphson iterative algorithm. The independence and convergence of the proposed model were verified, and its accuracy was validated via an analytical solution for crack width and a benchmark test for dynamic crack propagation. The propagation law of single/multicluster hydraulic fractures in coal seams with interlayers was investigated via the proposed model. The simulations revealed that the number of clusters and the mechanical properties of the interlayers significantly influence the fracture morphology. Finally, hydraulic fracturing of fracture-developed coal seams was simulated, confirming the potential of the proposed model.

Inertia Energy-Based Required Capacity Calculation of BESS for Achieving Carbon Neutrality in Korean Power System

Frequency response performance in power systems is becoming vulnerable due to the transition toward the higher penetration of renewable energy such as achieving carbon neutrality. In particular, reducing power system inertia energy as the asynchronous generation increases could result in violating the frequency stability constraint when a disturbance occurs in the power systems. In order to control the rapidly fluctuating frequency of the power system with low inertia, it is necessary to introduce fast frequency response resources such as a Battery Energy Storage System (BESS). This paper proposes a method to calculate the required capacity of BESS for compensating the frequency control performance of the power system using inertia energy. For calculating the required capacity of BESS, the inertia energy in the critical power system, where frequency control performance marginally satisfies frequency stability constraint, should be calculated. Also, the inertia energy in the evaluated power system having deficit inertia energy should be calculated. By comparing power systems that respond with different dynamics when the same disturbance occurs, the proposed calculation corresponds to the ratio of inertia energy deficiency based on critical power system inertia energy within the power imbalance. Through various case studies employing Korean power systems, the effectiveness of the inertia energy-based calculation method for the required BESS is verified by the fact that the BESS integrated power system marginally satisfies the frequency stability constraint. In these study cases, it is found that the instant response of BESS is very effective for compensating the frequency control performance of the low inertia power system. By applying the proposed method, it is also found that about 840 MW of BESS can achieve carbon neutrality in the Korean power system.

Exploring spectrum-based descriptors in pharmacological traits through quantitative structure property (QSPR) analysis

The study centered on Quantitative Structure Property Relationship (QSPR) analysis with a focus on various graph energies, investigating drugs like Mefloquinone, Sertraline, Niclosamide, Tizoxanide, PHA-690509, Ribavirin, Emricasan, and Sofosbuvir. Employing computational modeling techniques, the research aimed to uncover the correlations between the chemical structures of these medications and their unique properties. The results illuminated the quantitative relationships between structural characteristics and pharmacological traits, advancing our predictive capabilities. This research significantly contributes to medication discovery and design by providing essential insights into the structure-property connections of these medicinal compounds. Notably, certain spectrum-based descriptors, such as positive inertia energy, adjacency energy, arithmetic-geometric energy, first zegrab energy, and the harmonic index, exhibited strong correlation coefficients above 0.999. In contrast, well-known descriptors like the Extended adjacency, Laplacian and signless Laplacian spectral radii, and the first and second Zagreb Estrada indices showed weaker performance. The article emphasizes the application of graph energies and a linear regression model to predict pharmacological features effectively, enhancing the drug discovery process and aiding in targeted drug design by elucidating the relationship between molecular structure and pharmacological characteristics.

Methodological features of using of the element «squat»

The paper analyzes the technical element «squat», considers the options for its use in choreography and their interpretation in national associations, highlights the basic parts of this movement, typical for different squats. A general scheme of the «squat» element is proposed, which allows one to freely master and apply it, depending on the increase in the level of theoretical material and practical implementation, thus avoiding significant indicators that should be combined with technical development and a variety of assortment of this element of martial arts. Examples of the use of a squat in the form of a counterattack are given, using the energy of the body's inertia in the process of transition from a standing position to a crouching position. The effectiveness of plyometric exercises in the conditions of modern training and the possibility of their wide use in the form of such an element as a «squat» are considered. The expediency of using this element as a means of developing speed-strength abilities is also substantiated. Various classic and innovative options for using squats are presented, both in a practical and applied aspect, and in the aspect of effective development of physical qualities. Proposes the author's method of using the squat as an element of an applied nature, and as a means of developing speed-strength qualities.

The Relativistic Electrodynamics of Classical Charged Particles

Maxwell’s equations and the Lorentz force equation form the foundation of classical electromagnetic theory and their discovery led to the development of special relativity. Despite this achievement, their universal compatibility with the conservation of momentum and relativistic energy transformations is still debated. Incorporating effects of hidden momentum with the Lorentz force equation or using the Einstein–Laub formula are two common approaches to address some of these concerns. Which method to use, or if a change to classical electromagnetism is even required, remains controversial. A new theoretical approach is presented in this paper to address this using relativistic electromagnetic energy inertial frame transformations. These transformations identify a situation where an apparent violation of conservation laws could occur and how to consolidate this with electromagnetic theory. An explanation regarding the elementary nature of magnetism and the relationship between inertia and electromagnetic energy is also commented on.

Inferring the gravitational binding energy and moment of inertia of PSR J0030 + 0451 and PSR J0740 + 6620 from new universal relations

The neutron star interior composition explorer (NICER) recently simultaneously measured the gravitational mass (M g) and radius (R) of PSR J0030 + 0451 and PSR J0740 + 6620, respectively. Inspired by the groundbreaking observations, we establish two high accuracy universal relations (with the relative error at 1% level) related to M g and R to infer the gravitational binding energy (BE) (E g) and moment of inertia (I) of the two pulsars. By combining these universal relations with the data of (M g, R) released by NICER collaboration, the gravitational BE and moment of inertia of PSR J0030 + 0451 can be constrained within and g cm2 at 68% credible level, respectively. The gravitational BE and moment of inertia of PSR J0740 + 6620 can be constrained within and g cm2 at 68% credible level, respectively.

Pairing strength in the relativistic mean-field theory determined from the fission barrier heights of actinide nuclei and verified by pairing rotation and binding energies

Abstract We have studied the strength of the Bardeen–Cooper–Schrieffer (BCS) pairing force, used as a residual interaction to the relativistic mean-field approach, to reproduce the height of the inner fission barriers for actinide nuclei. It was found that increasing the pairing strength by about $13\%$ makes the reproduction of the inner fission barriers better over a wide range of actinide nuclei. This result was verified by using the moment of inertia of the pairing rotational energy, which was introduced to avoid mean-field and odd-mass effects in the pairing interaction, to deduce purely the pairing strength. The pairing interaction thus determined could also improve the description of the binding energy of heavy nuclei. As a result, a consistent picture among inner fission barrier, binding energy, and pairing moment of inertia could be obtained in terms of the relativistic mean-field + BCS theory for a broad region of the actinide nuclei.

Industry 4.0 and Proactive Works Council Members

Background: Integrating Industry 4.0 technologies in organizations affects employees’ workplaces and working conditions. Works Council members play an essential role in this because as intermediaries of information between employees and management, they increase mutual trust and help introduce changes in the work environment. This article discusses the Works Council members’ autopoietic endowments that are necessary for their proactive activity, which we discuss as building blocks for creating constructive relationships with management and quality energy in an organization. As such, we were interested in examining whether the autopoietic endowments of Works Council members influenced the type of relationship with the Works Council and management, and whether this relationship affected Works Council members’ organizational energy. Methods: A questionnaire was developed, piloted and distributed to Works Council Members, and 220 completed questionnaires were returned. Results: We found that the higher the level of self-awareness, the better the relationship between Works Council members and management. Moreover, poor energy represented poor relationships, and poor relationships signified a higher degree of resigned inertia and corrosive energy. Conclusions: Our research provides managements with insights into the relationship between employees and management, and the quality of their organizational energy.

Investigation of Alignment Effects of Neutron and Proton Pairs in High Spin States of Band Crossing for <sup>159,160</sup>Sm Isotopes Using Projected Shell Model (PSM)

Energy spectrum of nucleus is one the important information for better recognition of nuclear force and interaction of nucleon inside of the nucleus. Energy levels of nucleus are measured by detecting gamma- ray energy spectrum when a target nucleus bombarded with a special projectile to excite it in to levels higher than ground state. On the other hand, there are several models to calculate nuclear energy levels. Solution of the Schrödinger equation by considering a suitable potential is direct method to obtain energy levels of a quantum mechanical system like nucleus. Projected shell model is a model of this type that is developed by solving the Schrödinger equation for a set of potentials along with role of spin. Band structure and yrast bands for even-even and odd-even isotopes of Samarium (^159,160Sm) are calculated using a Fortran code founded based on the projected shell model (PSM). Energy levels of negative and positive parity bands of ¹⁵⁹Sm and ¹⁶⁰Sm isotopes of Samarium nucleus are obtained separately for each spin. Kinetic and dynamic moments of inertias are also calculated for these isotopes. The acquired results are compared with the experimental data. The electromagnetic reduced transition probabilities, B(M1)/B(E2) the behavior of dynamic moment of inertia J², rotational kinetic energy and moment of inertia J¹ as a function of spin have also been investigated and proper comparison is made between the calculated results and the experimental data. The alignment phenomena of neutron-proton pairs in view of the rotational movement in high spin states has also been studied with reference to band crossing.

Smart frequency control in low inertia energy systems based on frequency response techniques: A review

Integrated energy systems are considered as an indispensable part of the pathway towards a low-carbon sustainable future, as well as secure and reliable systems, characterised with a high level of flexibility and resilience. Increased penetration of renewable energy sources into energy systems is contributing to the reduction of carbon emission, thereby reducing the level or air pollution, climate changes and supporting the quality of life on the Earth. In this context, energy conversion systems realized by wind turbine generators have been and are still in the focus of extensive research on different system aspects, from planning, exploitation, monitoring, control, or protection perspective. To maximize the utilisation of available wind energy, modern wind turbine generators are connected to the main grid over power electronics (e.g. Type-3, or Type-4 wind generators). Consequently, they are electromagnetically disconnected from the rest of the power system and they provide little or no inertia, contrary to conventional synchronous generators, synchronously connected to the grid and synchronously operated to each other. This synchronism is necessary to ensure a stable system operation. The reduction of the system inertia imposes serious technical challenges on preserving system frequency stability. As it is known, inertia is one of key factors determining the robustness of power systems against sudden active power imbalances caused by different types of frequency events (generator disconnection, or load connection). The reduction of synchronous power reserves further intensifies this problem by reducing the system ability to maintain frequency within a permissible range following frequency events. Consequently, grid operators demand renewable energy sources, which are also referred to as nonsynchronous generators, to emulate the behaviour of synchronous generators to some extent and to participate in (fast) frequency control upon need. In general, countermeasures applied to these sources to contribute to frequency support are classified into two main categories: a) temporary and b) persistent energy reserve-based approaches. This paper presents a review on latest research findings and developed mechanisms for frequency control using wind energy conversion systems as the most frequently deployed renewable energy sources in modern power systems. Relying on lessons learned from the past two decades, in this paper current and future challenges, feasible solutions and subsequent research prospects are detailed. Some key principles that should underlie future changes of wind integrated energy systems are suggested and further research directions are addressed.

Design and fabrication of wave generator using an oscillating wedge

This paper describes the design and fabrication of a wave flume and associated equipment. The water wave generation by a triangle wedge is examined in this paper. Wave flume is fabricated by a concrete flume, which is 0.75-meter-wide, 1.3-meter-tall, and 11 meters long. One side of the flume is made of concrete, and the other side is made of clear mica sheets for observe the water wave profile. Wave flume is equipped with a triangle wedge located at one end of the wave flume, and this triangle wedge can be move along the rail of the wave flume. The passive wave absorber, which is made of honeycomb, which is located at the other end of the wave flume for absorbing energy waves generated from the wavemaker. The wedge is controlled by a desktop computer through Matlab software. The wedge can be controlled move up and down at a prescribed speed and oscillation amplitude corresponding to the desired wave height and wave frequency. At the middle flume is equipped microlaser distance sensor, which provides the data-logging capability. The microlaser distance sensor can collect wave height and wave period through a small ball, which is motioned in the tube, which is assembled on the water surface, and the small ball is very slight to avoid kinetic inertia energy. At the wavemaker is equipped with an Eccentricity Sensor, which is used to measure the wedge position to feedback for a desktop computer. Wave flume can generate the largest waves are about 0.2 meter high, a period about 1 second, and a wavelength of about 1.5 meters. The waves generated by an oscillating wedge have been measured, analyzed to consider the generated wave energy.

An Applicable Method to Improve Transient and Dynamic Performance of Power System Equipped With DFIG-Based Wind Turbines

The improvement of synchronous generators (SGs) stability is one of the most important issues in power systems. To this aim, doubly fed induction generator (DFIG) can be helpful. The main purpose of this paper is to improve both transient and dynamic performance of SG by using local DFIG-based wind turbines. Firstly, a transient controller (TC) is designed in controlling block of DFIG which changes its operating mode from generator to motor regime. Secondly, two damping controllers which are named electromagnetic torque band damping controller (ETBDC) and reactive power band damping controller (RPBDC) are suggested to improve dynamic stability of SG. Each damping controller includes three feedbacks namely, SG speed changes, SG electromagnetic torque and DFIG electromagnetic torque. Moreover, genetic algorithm (GA) is used to adjust these controlling parameters. The performance of TC is examined by comparison of system transient indexes such as critical clearing time (CCT), SG accelerating energy and DFIG inertia energy with and without using the proposed TC in a two-area test network. Similarly, system dynamic performance indexes such as overshoot, settling time, eigenvalue and damping torque of SG are compared with and without using two dynamic controllers. The obtained results show the effectiveness of proposed controllers.

Active Power Control of Wind Turbine Generators via Coordinated Rotor Speed and Pitch Angle Regulation

With increased wind power penetration in modern power systems, wind turbine generators (WTG) are expected to provide the active power control (APC) for tracking a desired power reference from system or wind farm operators. In practice, the pitch angle control (PAC) and the rotor speed control (RSC) methods can be used for APC in variable-speed variable-pitch WTGs, but the latter using turbine inertia as energy buffer is more attractive due to less pitch activation and higher wind energy production. For existing RSC methods, when the rotor speed reaches the upper speed limit at high wind speed or low power reference, they will actually become PAC to follow active power command, which also results in frequent pitch angle manipulation and considerable fatigue on the pitch servo system. To overcome this drawback, this paper proposes a new APC strategy integrating the rotor speed and pitch angle regulation. By utilizing the kinetic energy of rotor inertia at any pitch position (zero as well as non-zero pitch angle), this strategy can effectively avoid frequent action of pitch actuator while sustaining dispatched active power. The proposed method is verified by the fatigue, aerodynamics, structures, and turbulence-based simulations and wind turbine simulator-based experiments.

Experimental Study of Comfortableness during Hydrodynamic Torque Converter Lockup in a Construction Machinery

The comfortableness during hydrodynamic torque converter lockup in a construction machinery is investigated in this study. A motor grader is chosen as a typical construction machinery. Standard ramps are used to simulate stable working load. It is found that at conditions of flat road, the hydrodynamic torque converter locks at coupling condition, resulting in small acceleration fluctuation, little vibration dose value (VDV), and comfortable process. At ramp conditions, the hydrodynamic torque converter uses a traditional lockup strategy, which is possible to extend lockup status to higher load range. However, before the lockup process, the speed and torque differences between impeller and turbine wheels are larger. During the lockup process, the large speed difference leads to high engine inertia energy releasing rate. The large torque difference leads to high demanded engine torque change, which extends the engine adjustment ability and causes torque fluctuation. With a joint effect, three obvious acceleration fluctuations are observed, the VDVs become larger, and the lockup process becomes uncomfortable. As load increases, the comfortableness intends to get worse.

Master-slave wave farm systems based on energy filter with smoothed power output

Wave energy is an important renewable energy source. Previous studies of wave energy conversion (WEC) have focused on the maximum power take-off (PTO) techniques of a single machine. However, there is a lack of research on the energy and power quality of wave farm systems. Owing to the pulsating nature of ocean waves and popular PTO devices, the generated electrical power suffers from severe fluctuations. Existing solutions require extra energy storage and overrated power converters for wave power integration. In this study, we developed a master-slave wave farm system with rotor inertia energy storage; this system delivers self-smoothed power output to the grid and reduces the number of converters. Two control methods based on the moving average filter (MAF) and energy filter (EF) are proposed to smooth the output power of wave farms. RTDS simulations show that the proposed systems and control methods facilitate simple and smooth grid integration of wave energy.

A Three-dimensionalWave Activity Flux of Inertia–Gravity Waves and Its Application to a Rainstorm Event

A three-dimensional transformed Eulerian-mean (3D TEM) equation under a non-hydrostatic and non-geostrophic assumption is deduced in this study. The vertical component of the 3D wave activity flux deduced here is the primary difference from previous studies, which is suitable to mesoscale systems. Using the 3D TEM equation, the energy propagation of the inertia–gravity waves and how the generation and dissipation of the inertia–gravity waves drive the mean flow can be examined. During the mature stage of a heavy precipitation event, the maximum of the Eliassen–Palm (EP) flux divergence is primarily concentrated at the height of 10–14 km, where the energy of the inertia–gravity waves propagates forward (eastward) and upward. Examining the contribution of each term of the 3D TEM equation shows that the EP flux divergence is the primary contributor to the mean flow tendency. The EP flux divergence decelerates the zonal wind above and below the high-level jet at the height of 10 km and 15 km, and accelerates the high-level jet at the height of 12–14 km. This structure enhances the vertical wind shear of the environment and promotes the development of the rainstorm.

Clues to the Fundamental Nature of Gravity, Dark Energy and Dark Matter

This paper integrates the Flat Space Cosmology (FSC) model into the Friedmann equations containing a cosmological term. The Lambda term within this model scales according to 3H2t/c2 and 3/R2t. Use of the Bekenstein-Hawking definition of closed gravitational system total entropy provides for FSC cosmic parameter definitions in terms of . Cosmic time, radius, total matter mass-energy and vacuum energy in this model scale in exactly the same way as . This analysis opens the way for understanding gravity, dark energy and dark matter as being deeply connected with cosmic entropy. The recent theoretical work of Roger Penrose and Erik Verlinde is discussed in this context. The results of this FSC model analysis dovetail nicely with Verlinde’s work suggesting gravity as being fundamentally an emergent property of cosmic entropy. This emergent-property-of-entropy definition of gravity, if true, would also indicate that gravitational inertia, dark matter and dark energy are simply manifestations of cosmic entropy. Thus, they would likely have no identifiable connection to quantum physics, including the standard particle model.

Triboelectric Nanogenerator Enabled Body Sensor Network for Self-Powered Human Heart-Rate Monitoring.

Heart-rate monitoring plays a critical role in personal healthcare management. A low-cost, noninvasive, and user-friendly heart-rate monitoring system is highly desirable. Here, a self-powered wireless body sensor network (BSN) system is developed for heart-rate monitoring via integration of a downy-structure-based triboelectric nanogenerator (D-TENG), a power management circuit, a heart-rate sensor, a signal processing unit, and Bluetooth module for wireless data transmission. By converting the inertia energy of human walking into electric power, a maximum power of 2.28 mW with total conversion efficiency of 57.9% was delivered at low operation frequency, which is capable of immediately and sustainably driving the highly integrated BSN system. The acquired heart-rate signal by the sensor would be processed in the signal process circuit, sent to an external device via the Bluetooth module, and displayed on a personal cell phone in a real-time manner. Moreover, by combining a TENG-based generator and a TENG-based sensor, an all-TENG-based wireless BSN system was developed, realizing continuous and self-powered heart-rate monitoring. This work presents a potential method for personal heart-rate monitoring, featured as being self-powered, cost-effective, noninvasive, and user-friendly.

Coordinated Control of Wind Farms and MTDC Grids for System Frequency Support

This paper proposes a coordinated control strategy to provide system frequency support for separated main grids from offshore wind farms (WFs) that are integrated through multi-terminal DC (MTDC) system. The control strategy consists of two control loops including the MTDC frequency regulation loop (FRL) and the automatic WF power regulation loop (AWFPRL). In events of AC main grid disturbances, the former can re-dispatch MTDC grid power flow to support system frequency, while the latter can adjust wind power output accordingly through the variable frequency control of WF-connected converters. Inertia energy stored in wind turbines can be utilized to stabilize system frequency via MTDC grids. Moreover, wind power fluctuations can also be smoothed by the proposed control. An expression of frequency response coefficient is calculated, which is used to quantify the contribution of frequency support from offshore WF-connected MTDC system. Case studies have been conducted to demonstrate the effectiveness of the proposed control strategy using a four-terminal DC grid.