Search

A nonlinear finite element dynamic instability analysis of laminated composite stiffened plates subjected to in-plane harmonic edge loading is presented in this article along with the linear and nonlinear dynamic response study. The eight-noded isoparametric degenerated shell element and a compatible three-noded curved beam element are used to model the stiffened plates. Bolotin method is applied to analyze the dynamic instability regions in linear case. Incremental Harmonic Balance (IHB) method is applied to solve the nonlinear frequency response equations and Newmark-β method is used to solve the linear and nonlinear time history response equations. [ABSTRACT FROM AUTHOR]

Currently, power discrepancies between stacks are often overlooked when developing frequency response (FR) strategies for multi-stack alkaline water electrolyzer plants (AWEPs), which limits the full utilization of the plant's FR potential. To address this issue, this paper introduces a stack-level FR coefficient allocation strategy aimed at minimizing post-contingency frequency deviation. Specifically, the quantitative relationship between the operating power of alkaline water electrolyzer (AWE) stacks and steady-state frequency deviation is first derived, followed by the formulation of an optimal FR problem. The solution to this problem is an FR strategy based on the principle of equal frequency deviation, which optimally allocates FR coefficients among AWE stacks according to their operating power, thereby maximizing the plant's FR support capacity. Equivalent circuit model-based case study demonstrates that, compared to existing strategies, the proposed approach achieves a more balanced power distribution among the stacks during the FR process. This even power allocation not only reduces post-contingency frequency deviation but also enhances productivity and streamlines production management in the AWEP, thereby increasing the plant owner's willingness to participate in FR. Specifically, the proposed strategy results in a 29.3% reduction in post-contingency frequency deviation, a 1.8% improvement in production efficiency under a 10 MW power imbalance, a 2.3% increase in hydrogen production rate under a 4 MW power imbalance, and more stable operation under a 16 MW power imbalance. • Derive quantitative relationship between electrolyzer power and system frequency. • Strategy to optimally distribute frequency response coefficient among stacks. • Achieving a 29.3% frequency deviation reduction and higher production efficiency. [ABSTRACT FROM AUTHOR]

Engineering rock masses typically feature natural discontinuities that span different scales, with filled joints as macroscopic discontinuities and microdefects as mesoscopic ones. However, the mechanism of wave propagation in the filled joints has been unclear. This study develops a novel dual-scale equivalent rock model to investigate the wave propagation in jointed rock masses. Firstly, two combination models at different scales were developed by using thin layers and contact interfaces to simulate filled joints and microdefects, respectively. Subsequently, a wave propagation equation was derived through a time-domain recursive method, and validated against the experimental data and the predictions of traditional models. Finally, a parametric analysis was conducted on the frequency response of wave propagation in jointed rock masses. The results show that this novel model can describe the wave dispersion and attenuation in dual-scale discontinuous rock masses, and its equation exhibits robustness. It is revealed that two independent mechanisms induce the wave dispersion in a single joint: multiple wave reflections inside the joint and the viscosity of the filling material. The effect of microdefects on wave attenuation mainly depends on propagation distance, while the influence of filled joints on wave propagation can be determined by the quality factor, thickness, effective wave velocity, and density of the filling. The wave velocity of the filling has a significantly higher influence on the transmission coefficient than the filling density. This challenges the conventional concept that the wave impedance of filling is a basic parameter for estimating the transmission coefficient. Highlights: A novel dual-scale equivalent model was proposed for wave propagation in jointed rock masses. The multiple reflection effects at rock joints were revealed to be the main cause of wave dispersion. Using wave impedance of joint filling to predict the transmission coefficient was found to be inaccurate. The frequency response difference in macroscopic and mesoscopic discontinuities of rock masses was revealed. [ABSTRACT FROM AUTHOR]

A novel model reduction method for viscously damped structures with statically determinate interfaces, such as spacecraft flexible appendages, is proposed. The paper presents a derivation of the complete complex modal expansion of the interface dynamic stiffness of these structures. Based on the identity relation for all complex modes, which is obtained during the derivation, it is found that the interface acceleration impedance can be expressed as a rational fraction with high accuracy using only low-order complex modes. Using this rational fraction as an approximation model, numerical results of the frequency response can be fitted. The fitted interface acceleration impedance can be applied to real-time control as a reduced model in the form of a transfer function. Furthermore, it can be transformed into the form of system matrices by introducing auxiliary variables, which then participate in the dynamic analysis of the assembly. The reduction process circumvents complex modal analysis and necessitates only the results of frequency responses. Thanks to the powerful ability of conventional finite element software to perform frequency response analysis, this reduction method can be used for large-scale complex models in actual engineering applications. [ABSTRACT FROM AUTHOR]

Sound source localization is a critical task in various applications. However, it becomes challenging when the sound sources are not directly visible to the sensors due to obstacles or other environmental factors. This paper proposes a novel approach for locating sound sources in non-line-of-sight environments by combining the equivalent source method (ESM) with the time reversal method (TRM). The ESM is used to compute the frequency responses between the focusing points and the measurement points numerically. These frequency responses are then substituted to the TRM to localize the sound sources. To evaluate the performance of the proposed method, it is tested through numerical simulations and an experiment. The results prove that the ESM can compute the frequency responses accurately, and the combination of TRM and ESM effectively localizes sound sources in non-line-of-sight environments. [ABSTRACT FROM AUTHOR]

This work proposes a methodology to determine the height difference of the guideways of machine tools where two guideways are not placed on the same horizontal plane. Firstly, a rigid–flexible coupling system consisting of a moving rigid mass and an elastic overhanging beam is presented as an equivalent mechanical model of a column and a spindle box. Then, the relationship between the deviation of a reference point and the height difference or the spindle box's stroke is modeled. Next, the natural frequency and mode shape function of the overhanging beam, and the frequency response functions of the coupling system, are derived. The results indicate that there always exists an optimal height difference minimizing the relative deflection over the stroke of the moving part, and the optimal value depends on the loads in two directions and the stroke of the moving part. Similarly, there is also an optimal choice maximizing the first-order resonant frequency of the coupling system; however, the optimal solutions for both static and dynamic cases are not the same. This work provides beneficial instruction for choosing the height difference of machine tools with two guideways on a bed that are not on the same plane. [ABSTRACT FROM AUTHOR]

The objective of this paper is to first present some issues with impulse invariance filter (IIF) design during the design of digital infinite impulse response (IIR) filters. Engineers are often confused about some inconsistent observations. For instance, if the impulse response of a digital filter is designed using the impulse invariance procedure, then the analog and digital filters' frequency and step responses are very different. Two simple remedies are presented in this paper. One is a post-processing approach that scales the frequency and step responses of the digital filter by the sampling interval T. Another one is a pre-processing approach that scales the impulse response of the analog filter by T. However, even after these remedies, there is still a steady state bias in the step response of the digital filter for certain cases where there is discontinuity in the analog impulse response. A recommendation is to include a correction term in the digital filter. After that, the steady state bias in the digital filter is then suppressed. Moreover, the MATLAB R2021a command "impinvar" needs to also include a correction term so that the frequency and step responses can be more accurate in the digital filter. Two comparative studies were carried out to compare the improved IIF filter with three competing digital IIR filter design methods. Although the above issues and improvements have been proposed by researchers in the past, many researchers, engineers, and students are still not aware of them. This paper provides a fresh revisit of these issues and improvements by using figures, equations, and examples. Proper credits are also given to those researchers who first pointed out those issues and improvements. It is hoped that through an open access journal, future rediscovery of issues and improvements in IIF can be prevented. [ABSTRACT FROM AUTHOR]

Zeolite 13X is an excellent candidate for the capture of CO2. However, this system needs to be investigated in more detail with regard to adsorption and diffusion. For this purpose, frequency response (FR) measurements were carried out with binderless zeolite 13X (NaMSX) and CO2. The size of the particles and the sample amount were modified in order to investigate their effects on diffusion processes. Macropore diffusion was detected and the corresponding diffusion coefficients were determined. The mentioned system was additionally used to evaluate the performance of the in‐house FR apparatus. [ABSTRACT FROM AUTHOR]

Deep scattering layers (DSL) in oligotrophic systems are typically comprised of a variety of coexisting organisms, including fish, zooplankton, jellyfish, and squid, and hence there is uncertainty about the proportion of the acoustic backscatter in these layers that can be attributed to mesopelagic fish. Here, acoustic targets were classified using a multi-frequency acoustic classification algorithm based on data collected in the Indian Ocean at 18, 38, 70, and 120 kHz during three acoustic surveys in 2018. Frequency-dependent backscattering strength information (∆Sv) was extracted from acoustic data that coincided with trawl hauls dominated by mesopelagic fish. Five ∆Sv frequency pairs were used to separate the acoustic backscattering into three broad scattering categories, i.e. mesopelagic fish, crustacean-like/tunicates, and squids/others. Results indicated that the DSL is highly diverse and dominated by mesopelagic fish, with average densities at a regional scale ranging from 12.0 (±10.9) to 26.0 (±21.7) g m−2, and proportions of the acoustic backscatter attributed to mesopelagic fish ranging from 0.5 to 0.7. These estimates are generally lower than previously estimated for other regions of the Indian Ocean. The situation may well be similar elsewhere, particularly in oligotrophic systems, with potential ramifications for global mesopelagic fish biomass estimates. [ABSTRACT FROM AUTHOR]

Lake Victoria is the second-largest freshwater lake in the world, and fish from the lake are a vital food resource for millions of people living around it. The silver cyprinid (Rastrineobola argentea) , a small schooling pelagic species known in Tanzania as "dagaa" contributes ca. 55% to the total annual catch (ca. 0.51 million tonnes (MT) in 2014). The acoustic target strength (TS, dB re 1 m2) of dagaa, a key factor for biomass estimation, is however not well described, and is a major source of uncertainty in biomass estimation. In this study, we developed a Kirchhoff-ray mode (KRM) model to predict the TS of dagaa at standard fisheries survey frequencies. The model was based on the morphology of the body and the dual-chambered swimbladder, as obtained from X-ray images of fish ranging in total length (TL) between 2.8 and 5.4 cm. The results suggested that the swimbladder (which comprises 2.6 to 8.2% of body volume) accounts for ca. 65 to 90% of the total backscattering at 120 kHz. The predicted TS was highly dependent on tilt angle, varying by 14.0 dB at 120 kHz across the tilt range 65–115˚ (where 0˚ is head up and 180˚ is tail up), and TS variability with tilt generally increased with increasing frequency. The tilt angle of acoustically tracked individual fish indicated a distribution of tilt angles with a mean and s.d. of 93.5 and 15.1°. Our model suggested a new tilt-averaged TS–TL relationship for dagaa [ |$T{S}_{120\ kHz} = 19.49\log ({TL}) - 70.3$| ], which leads to a TS 1.5 dB higher than the value in the relationship presently used to estimate stock biomass. The new relationship will lead to a substantial reduction (by ca. 30%) in estimated biomass. The discrepancies between the mean relative frequency response of the in situ measurements of backscatter from dagaa and the KRM model predictions were in the range of -2.9–3.1 dB at frequencies from 45 to 250 kHz. The KRM modelling and in situ broadband measurements of dagaa will be beneficial for acoustic identification and behavioural studies of dagaa, and will enable improved biomass assessment, thereby underpinning sustainable long-term management. [ABSTRACT FROM AUTHOR]

Power electronic converters are important elements of many modern devices. Therefore, there is a need for a thorough analysis of their behavior and the ability to properly control them. Typically, the converter's dynamics are investigated using the small-signal averaging method, which does not provide detailed information about the converter. In particular, it does not account for the switching ripple effect. In this paper, a novel switched state–space model of the interleaved step-up DC–DC converter is introduced. That model incorporates high-frequency information, which allows for a more in-depth dynamics analysis. The results, i.e., step and frequency responses, obtained from both theoretical models are compared to the interleaved step-up DC–DC converter model implemented in PSpice ver. 16.6 from Cadence Design Systems. [ABSTRACT FROM AUTHOR]

In recent years, the "asset management" or "managing assets" technique has been expected to support the rationalization of the maintenance and operation of electric power equipment, especially as a countermeasure for aging equipment. For this purpose, the development of diagnostic methods for aging, remaining life, and faults is necessary. Furthermore, it is important to accumulate case studies applying such diagnostic methods to real equipment and the analysing benefits of the applications of the diagnostic methods. In this report, frequency response analysis and a partial discharge measurement are applied to a shunt reactor suspected of occurrence of partial discharge. Results of the diagnostic methods suggest the breakage of the earth bar connecting the iron‐core blocks and the occurrence of the partial discharge at the iron core. From these diagnostic findings, the shunt‐reactor operator decided to postpone the replacement for 2 years, compared with the case where no diagnostic methods were applied. In this report, the benefits of deciding the postponement is also evaluated. [ABSTRACT FROM AUTHOR]

In this paper, a discussion on the forced vibration of a transversely isotropic piezoelectric plate with finite dimensions subjected to a time-harmonic force resting on a rigid foundation is carried out. Here, we assume that the plate is poled along the perpendicular surface and bi-axial initially stressed in their reference configuration. The three-dimensional linearized theory of electro-elastic waves in initially stressed bodies (TLTEEWISB) is applied to the initially-stressed piezoelectric plate. A general formulation of the governing equations of motions is provided according to the piece-wise homogeneous body model, and then the three-dimensional finite element modeling (3D-FEM) is developed as a solution procedure in terms of weak formulation and virtual work principle. The objective of this paper is to present the results regarding the frequency response of the piezoelectric rectangular plate and the influence of the initial stress factor on the system. Numerical examples imply that while the increasing aspect ratio of the plate prevents the resonance mode of the dynamic force, the increasing thickness ratio exceeds this mode. Further, it is also demonstrated and discussed in detail that the initial stress state has a considerable influence on this mode. [ABSTRACT FROM AUTHOR]

Abstract Large‐scale integration of renewable energy into the power grid results in a lack of system inertia, posing challenges to the optimal operation and scheduling of systems considering frequency stability. This article proposes a unit commitment model that considers both inertia constraints and the uncertainty of load and renewable energy. First, the time‐domain expression of the system frequency response is calculated based on the aggregated System Frequency Response (SFR) model, considering the system's maximum frequency deviation and the maximum Rate of Change of Frequency (RoCoF) limit. This calculation determines the minimum inertia requirement for the system. Furthermore, inertia constraints suitable for mixed‐integer programming model are derived to address the nonlinearity of conventional frequency constraints. Second, considering the uncertainties of load and wind energy from renewable sources, a unit commitment model with inertia constraints is constructed, and a robust method is used to solve the uncertainties. Finally, the accuracy of the proposed inertia constraints and unit commitment model is validated using case study of IEEE standard test cases and a provincial power grid in China.

Abstract The increasing penetration of grid‐following voltage source converters (GFL‐VSCs) in the power grid has changed the frequency dynamics of the system. GFL‐VSC follows the frequency of the terminal bus using a phase‐locked loop, therefore it does not establish the frequency in the same manner as a synchronous generator. However, previous research has demonstrated that GFL‐VSC without additional frequency controls not only tracks the terminal frequency during the system dynamic process bus also has an influence on it, and derives the relationship between GFL‐VSC and terminal frequency through a simplified model. This paper further derives a more generic relationship considering the influences of q‐axis current and grid voltage amplitude variation, which were ignored in previous research. The relationship has proven to be effective and valid. Several influencing factors are analysed to describe the ability to modify terminal frequency. Then the effect of GFL‐VSCs on the frequency distribution of power grid is studied. The frequency divider formula is improved by incorporating the relationship, which provides a frequency estimation formula applicable for system with multiple GFL‐VSCs. Two system‐level simulations verify the conclusion and related influencing factors are analysed.

Abstract In recent years, the “asset management” or “managing assets” technique has been expected to support the rationalization of the maintenance and operation of electric power equipment, especially as a countermeasure for aging equipment. For this purpose, the development of diagnostic methods for aging, remaining life, and faults is necessary. Furthermore, it is important to accumulate case studies applying such diagnostic methods to real equipment and the analysing benefits of the applications of the diagnostic methods. In this report, frequency response analysis and a partial discharge measurement are applied to a shunt reactor suspected of occurrence of partial discharge. Results of the diagnostic methods suggest the breakage of the earth bar connecting the iron‐core blocks and the occurrence of the partial discharge at the iron core. From these diagnostic findings, the shunt‐reactor operator decided to postpone the replacement for 2 years, compared with the case where no diagnostic methods were applied. In this report, the benefits of deciding the postponement is also evaluated.

The dynamic response of a thermoplastic composite sandwich structure is optimized under random vibration. First, the experimental modal analysis data of a set of test samples are processed by a sequential set of statistical analysis such as descriptive statistics, factor analysis, and paired sample t-test. Then, the sample with the highest ability to represent the group is taken as the reference data. Three different computational models, which are defined according to whether the solid to be meshed is considered an area or a volume, are constructed. Modal analysis results of the computational models are compared to the reference experimental data to evaluate the performance of the models. To predict the dynamic response of the sandwich beam, it is excited through a random signal in the transverse direction. The nodal acceleration responses are computed in 17 evenly spaced points located on the upper finishing layer of the sandwich beam. Finally, a geometry optimization study is conducted to predict the optimum thicknesses of the 7 layers bonded together to form the sandwich beam. The optimum layer thicknesses that minimize the nodal accelerations at 17 evenly spaced points on the sandwich beam are computed. The current study shows that the shell model has the closest values to the experimental data compared to other models. As far as the dynamic response of a TPC sandwich structure is concerned, it is concluded that the shell model better represents the structure during the modeling phase and leads to concurrently reduced weight and nodal acceleration, when optimized. [ABSTRACT FROM AUTHOR]

ObjectivesThe large-scale penetration of wind power has reduced the frequency regulation capability of the power system to a certain extent.As a relatively mature and effective technical means, the energy storage system is widely used in power grid frequency regulation. Therefore, the response process and optimal configuration of energy storage system (ESS) participating in power grid frequency regulation under the control of virtual synchronous generator were studied.MethodsBased on the simulation software DIgSILENT/PowerFactory, an ESS control model and typical power system were constructed to analyze the frequency response characteristics of the grid before and after the ESS participation. Furthermore, considering the reserve capacity of wind turbines under different output modes, the configuration results of the ESS were optimized by dividing the wind speed range and determining the wind turbine power reserve coefficient, so as to realize the adaptive adjustment of the frequency regulation coefficient of the ESS.ResultsThe investment of the ESS can effectively improve the frequency response and reduce wind curtailment of the system. By reserving the frequency regulation capacity of wind turbines reasonably, the ESS can provide reliable power support for the power grid.ConclusionsThe self-adaptive adjustment method of the frequency regulation coefficient of the ESS based on the wind speed and the output power of fans can effectively reduce the overshoot and the output power of the ESS while meeting the frequency regulation requirements, thereby extending the working time.

Abstract Recent years have seen high penetration of renewable energies, which have significantly reduced the inertia of bulk power systems. As a result, the frequency behaviour of power systems is becoming more complex. To resolve this technical challenge, there is a particularly strong interest in developing analytical solutions for frequency dynamics studies. This study first describes a second‐order frequency dynamics model for power systems with renewable energies. A non‐linear perturbation approach is suggested to drive the analytical solution of the model. It is shown that, under many circumstances, frequency dynamics can be effectively approximated using a linear model. Subsequently, the article describes a fourth‐order linear frequency dynamics model that takes into account governor‐turbines. A polynomial eigenvalue method is proposed to identify the dominant and non‐dominant modes of the solution of the four‐order model. It is demonstrated that the dominant mode has a decisive impact on frequency behaviour, while the non‐dominant modes influence the relative frequency oscillations only. Finally, the study derives the analytical expressions of the standard frequency performance metrics and examines the impact of damping and inertia parameters. The introduced results are verified using two test systems, demonstrating the accuracy and effectiveness of the suggested method.

Abstract Precisely interpreting frequency response analysis (FRA) curves is crucial when investigating mechanical malfunctions in power transformer windings (TWs). However, many conventional explanations of FRA features cannot be validated by an equivalent circuit (EC) that represents winding structures using resistance, inductance, and capacitance components in a ladder network. Incorrect interpretation can lead to misdiagnosis and confusion in asset management. Previous ECs are often proposed by analysing winding structures without rigorous verification compared to the corresponding FRA data. The specific EC is acquired using the transfer function (TF) derived from the measured FRA data. This allows for the establishment of the relationship between TW FRA curves, TF equations, and EC topologies. The precise interpretation of FRA curves can be achieved by closely observing the FRA curves created from TFs and ECs. The remarkable similarity between the measured and modelled FRA curves verifies the authenticity of the derived ECs. This significant achievement clarifies many misunderstandings regarding FRA and represents a substantial advancement in FRA technology.

In high-penetration wind power generation systems， accurately assessing the support potential for virtual inertia of energy storage and fully releasing its energy reserves to render the systems active in grid frequency regulation are crucial for ensuring the systems’ frequency safety and stability. To achieve this， a dynamic frequency response model for wind-storage power generation systems to calculate the system’s time of safe frequency rise and fall and the extreme values of frequency deviation. Next， considering the constraints on the safe operating condition of the state of charge （SOC） during energy storage， the virtual inertia of energy storage during the time of safe frequency rise and fall is quantitatively evaluated. Moreover， an active frequency support technology for energy storage based on fixed-frequency control is introduced， aiming to fully exploit the frequency support capability of energy storage during the frequency drop and recovery periods. Finally， a simulation model of high-penetration wind power generation systems is constructed for validation. Under the proposed control strategy， energy storage can provide effective inertia support and offer sustained frequency response， thereby significantly enhancing the systems’ frequency stability.

Recent years have seen high penetration of renewable energies, which have significantly reduced the inertia of bulk power systems. As a result, the frequency behaviour of power systems is becoming more complex. To resolve this technical challenge, there is a particularly strong interest in developing analytical solutions for frequency dynamics studies. This study first describes a second‐order frequency dynamics model for power systems with renewable energies. A non‐linear perturbation approach is suggested to drive the analytical solution of the model. It is shown that, under many circumstances, frequency dynamics can be effectively approximated using a linear model. Subsequently, the article describes a fourth‐order linear frequency dynamics model that takes into account governor‐turbines. A polynomial eigenvalue method is proposed to identify the dominant and non‐dominant modes of the solution of the four‐order model. It is demonstrated that the dominant mode has a decisive impact on frequency behaviour, while the non‐dominant modes influence the relative frequency oscillations only. Finally, the study derives the analytical expressions of the standard frequency performance metrics and examines the impact of damping and inertia parameters. The introduced results are verified using two test systems, demonstrating the accuracy and effectiveness of the suggested method. [ABSTRACT FROM AUTHOR]

In the case of strong coupling, analyzing a complex system by finite element method costs so much due to the degrees of freedom. Although introducing modal superposition technique is able to reduce the sum of coupling system's freedoms, it is still based on the assumption of neglecting the coupling influence between the high-order modes and low-order modes belonging to different subsystems. And it may result in non-convergence when uncoupling modes are used. Based on the undamped acoustic and vibration coupling equation, this paper presents a new coupling method called patch transfer function method (PTFM), by which the coupling face is tackled as a series of independent patches. The patch transfer functions of each patch are calculated by the average value of the nodal value, then the coupling system PTFs can be obtained by the continuity equation. It is faster to predict the coupling system response, as the inversion of coupling equation is substituted for the transfer function from source to receiver. At last, with the model of plate and air-cavity coupling system, this paper reveals the accuracy of PTFM by comparing the result of direct coupling method (DCM). And the theory and calculation error of the method are discussed. [ABSTRACT FROM AUTHOR]

The advancement in material platforms exhibiting strong and robust electro-optic effects is crucial for further progress in developing highly efficient and miniaturized optoelectronic components with low power consumption for modern optical communication systems. In this work, we investigate thin-film lead zirconate titanate (PZT) substrates grown by a chemical solution deposition technique as a potential platform for on-chip plasmonic electro-optic modulators. A high modulation depth (>40 %) is achieved with 15 μm-long electro-optic directional coupler modulators. An unusual cutoff in the modulation frequency response at ∼200 kHz is observed and further studied with respect to possible reorientation effects. Second-harmonic generation signals are found influenced by the externally applied electric field, indicating that the domain reorientation effect can be responsible for the unusual frequency response observed. [ABSTRACT FROM AUTHOR]

Copyright of Power Generation Technology is the property of Power Generation Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The battery management system is employed to monitor the external temperature of the lithium-ion battery in order to detect any potential overheating. However, this outside–in detection method often suffers from a lag and is therefore unable to accurately predict the battery's real-time state. Herein, an inside–out frequency response approach is used to accurately monitor the battery's state at various temperatures in real-time and correlate it with the solid electrolyte interphase (SEI) evolution of the graphite electrode. The SEI evolution at temperatures of −15, 25, 60, and 90 °C exhibits certain regular characteristics with temperature change. At a temperature of −15 °C, the Li+-solvent interaction of lithium-ion slowed down, resulting in a significant reduction in performance. At 25 °C, a LiF-rich inorganic SEI was identified as forming, which facilitated lithium-ion transportation. However, high temperatures would induce decomposition of lithium hexafluorophosphate (LiPF6) and lithium-ion electrolyte. At the extreme temperature of 90 °C, the SEI would be organic-rich, and LixPyFz, a decomposition product of lithium salts, was further oxidized to LixPOyFz, which led to a surge in the charge-transfer resistance at SEI (Rsei) and a reduction in Coulombic efficiency (CE). This changing relationship can be recorded in real time from the inside out by electrochemical impedance spectroscopy (EIS) testing. This provides a new theoretical basis for the structural evolution of lithium-ion batteries and the regular characterization of EIS. [ABSTRACT FROM AUTHOR]

A soft piezoceramic multilayer (ML) bending thin and thick dual-actuators side-by-side device, for use in bone-conduction hearing aids (BCHA), was characterized experimentally. For this purpose, first, quasi-static (0.1 Hz square wave) transverse displacements (deflections) of each ML bender were measured using a laser vibrometer (LV) under unimorph and bimorph drivings at various non-amplified peak (p) voltages (1Vp–13Vp). The resulting peak displacement–voltage curves were found clearly nonlinear, indicating a pronounced piezoelectric (PE) field-dependent nonlinearity (FDNL). Then, experimental electric impedance analyses were conducted for each ML bender, using an impedance analyzer, under 1Vpunimorph driving for the whole audio frequency range (20 Hz–20 kHz). The identified three modes' superposed impedance magnitudes and phases showed their increasing deviation to the frequency scale left with increasing the modes' order, indicating a possible softening elastic FDNL, as confirmed later by harmonic frequency response LV measurements at 1Vp. Finally, the harmonic frequency responses, for the above audio frequency range, were measured for each ML bender using the LV under unimorph and bimorph drivings at various non-amplified voltages (1Vp–10Vp). Here, beside the PE FDNL, the frequency response functions showed clearly a pronounced softening elastic FDNL. Consequently, with increasing input voltages, the identified two modes' displacement amplitudes were nonlinearly increasing, while resonant frequencies and corresponding quality factors were nonlinearly decreasing. The three parameters-voltage curves were found to fit well (R2 ≈ 1) with high-order polynomials. These experimental results contradict the widely assumed displacement–potential linearity of middle ear or BCHA implantable PE vibrators of open literature available types (with or without shim bimorphs, unimorphs or diaphragms, and stacks) under similar targeted driving voltage and frequency ranges. The ML benders type quasi-static, frequency response and electric impedance characterizations, as well as the dual actuators side-by-side device, are proposed here for the first time for hearing aid applications. [ABSTRACT FROM AUTHOR]

In this paper, based on distributed transfer function method (DTFM), the closed-form analytical solutions for vibrations of Euler–Bernoulli beam and frame structures with arbitrary number of cracks are studied. First, generalized DTFM is employed to characterize the dynamical model for a single cracked beam and its analytical solutions for eigenvalue problem and frequency response are obtained. Then, a new DTFM cracked element that encapsulates one crack of arbitrary location inside the beam is proposed. Using the DTFM cracked element and global dynamic stiffness matrix assembly technique, damaged frame structures of arbitrary form can be modeled for vibration analysis. Previous analytical methods only addressed low-frequency vibration of simple cracked beam structures, the proposed method can yield analytical solutions in the medium- and high-frequency regions, which is critical for the small crack detection in complex frames. Lastly, three numerical examples are given to illustrate the correctness and effectiveness of the DTFM in analyzing natural frequencies, modal shapes and frequency responses for cracked structures. By comparing with the Finite Element Method (FEM) and benchmarks from literatures, we proved that the DTFM has better performances in terms of accuracy and efficiency. [ABSTRACT FROM AUTHOR]

The sustainable development of an area is highly reliant on a reliable electrical energy supply. Microgrids are important in integrating distributed energy resources (DERs) using power electronic converters. However, microgrid control becomes challenging with the increasing number of distributed generators and loads. With the conventional droop control method, power contributions from DER converters cannot be accurately shared due to a mismatch of line impedances. In this paper, an augmented hierarchical control mechanism is proposed to solve the issues mentioned above. This hierarchical control mechanism consists of primary and secondary controllers. The primary stage utilized the droop controller to improve optimal power flow, mainly for the resistive network. The secondary stage is based on an improved methodology to compensate for the voltage and frequency variations during small and large signal disturbances. Moreover, the modelling and analysis for PMSG-based wind energy conversion systems are also presented. The response of the primary controller for active and reactive power sharing is investigated. The analysis emphasizes the demonstration of optimal power-sharing under normal and abnormal conditions for the considered load. Finally, the suggested robust controller's performance is evaluated in a MATLAB environment, and simulation results show the proposed scheme's superiority under different operating conditions. The frequency is stable at 50 Hz after a 50 KW load is added. [ABSTRACT FROM AUTHOR]

The transverse static load, resultant from self-weight, significantly impacts both the response and the nonlinear dynamic behavior of a flexible inclined cantilever with a large lumping tip mass under harmonic base motion. However, the transverse static load was not taken into account and the mode shape of a pure cantilever beam was directly adopted during Galerkin’s procedure in the formulations of a cantilever carrying a large lumping tip mass in many previous studies. In this paper, (1) the static load effect caused by the self-weight in an inclined cantilever is considered by using a coordinate transformation, (2) the efficacy of adopting a pure cantilever beam mode shape to analyze a cantilever beam carrying a large lumping mass is studied and (3) a recently proposed semi-analytical method named parameter-splitting multiple-scales method is extended to analyze the cantilever studied to examine its effectiveness. First, the extended Hamilton’s principle is utilized to formulate the equation of motion of the cantilever studied. After that, the mode shape of a pure cantilever and the exact mode shape of a cantilever carrying a lumping mass are separately adopted in Galerkin’s method to transform the partial differential equation into ordinary differential equations. The frequency-response curves of the discretized nonlinear differential equations obtained by the numerical continuation method and the parameter-splitting multiple-scales method are compared to address ① the transverse static load effect on the frequency-response and nonlinear dynamical behavior of the beam, ② the discrepancies between the resultant frequency-response curves obtained by using two different mode shapes and ③ the efficacy of the parameter-splitting multiple-scales method on solving strongly nonlinear practical problem. [ABSTRACT FROM AUTHOR]

The dynamic response of a railway bridge depends on several parameters; the primary parameter is the fundamental natural frequency of vibration of the bridge itself. It is considered a critical parameter of the bridge as the driving or the forcing frequencies arising from moving trains may coincide with the fundamental frequency of the bridge and initiate a resonant response amplifying the bridge load effects. This condition may adversely affect the stresses experienced on bridge members and, consequently, the remaining fatigue life of the structure. Because the train adds additional time-varying mass to the bridge, this introduces a time-varying change in the bridge's fundamental natural frequency of vibration. As a result, train critical speeds will have a certain range depending on the train configuration. This article presents a simplified method using a power-law relationship to predict the frequency characteristics of a bridge as a function of the train-to-bridge mass ratio. The method is presented in a generalized form, which enables the frequency characteristics to be determined for any given combination of trains and simply supported bridges of short to medium span typically found on the UK rail network. The method is then demonstrated in a case study of a single-span, simply supported plate girder bridge. By considering the BS-5400 train traffic types, the proposed method is used to calculate bridge frequency effects, dynamic amplification, and train critical speed bandwidth for each train type. The simplicity of the proposed method, as it does not require any complex computational modeling, makes it an ideal and effective tool for the practicing engineer to carry out a quick and economical assessment of a bridge for any given train configuration. [ABSTRACT FROM AUTHOR]

Highlights: A novel method is developed for precise control over the structure of 3D anodic aluminum oxide templates, enabling fine-tuning of both the vertical pore diameter and interspace within the templates. 3D carbon tube nanoarrays featuring significantly thinner and denser tubes are constructed as high-quality electrodes for miniaturized filter capacitors. The 3D compactly arranged carbon tube-based capacitor achieves a remarkable specific areal capacitance of 3.23 mF cm−2 with a phase angle of − 80.2° at 120 Hz. Electric double-layer capacitors (EDLCs) with fast frequency response are regarded as small-scale alternatives to the commercial bulky aluminum electrolytic capacitors. Creating carbon-based nanoarray electrodes with precise alignment and smooth ion channels is crucial for enhancing EDLCs' performance. However, controlling the density of macropore-dominated nanoarray electrodes poses challenges in boosting the capacitance of line-filtering EDLCs. Herein, a simple technique to finely adjust the vertical-pore diameter and inter-spacing in three-dimensional nanoporous anodic aluminum oxide (3D-AAO) template is achieved, and 3D compactly arranged carbon tube (3D-CACT) nanoarrays are created as electrodes for symmetrical EDLCs using nanoporous 3D-AAO template-assisted chemical vapor deposition of carbon. The 3D-CACT electrodes demonstrate a high surface area of 253.0 m2 g−1, a D/G band intensity ratio of 0.94, and a C/O atomic ratio of 8. As a result, the high-density 3D-CT nanoarray-based sandwich-type EDLCs demonstrate a record high specific areal capacitance of 3.23 mF cm−2 at 120 Hz and exceptional fast frequency response due to the vertically aligned and highly ordered nanoarray of closely packed CT units. The 3D-CT nanoarray electrode-based EDLCs could serve as line filters in integrated circuits, aiding power system miniaturization. [ABSTRACT FROM AUTHOR]

Tropical tuna fisheries support some of the largest artisanal and industrial fisheries worldwide. Approximately 37% of the tropical tuna catch by industrial purse seiners is obtained from tuna associated with drifting fish aggregating devices (DFADs), where three tuna species coexist: skipjack (Katsuwonus pelamis) , bigeye (Thunnus obesus), and yellowfin tuna (Thunnus albacares) , with stocks subject to different health status. Purse seine fishers heavily rely on acoustic technology to detect and assess the quantity of tuna at DFADs. Yet, accurately distinguishing between species using solely acoustic methods is limited by insufficient knowledge about each species' acoustic response across frequencies. This study was carried out on six swimbladdered individuals belonging to two sets with mean lengths of 51.9 ± 9.5 and 52.9 ± 2 cm. It focuses on the frequency response obtained from ex situ measurements of yellowfin tuna recorded at 38, 70, 120, and 200 kHz, which revealed a flat response across frequencies, with b20 values of −72.4 ± 9, −73.2 ± 8, -72.3 ± 8, and −72.3 ± 9 dB, respectively. These results, contrast with previous findings on bigeye and skipjack, demonstrating the discrimination potential of acoustics in these three species. To harness this potential, a discrimination algorithm was developed. [ABSTRACT FROM AUTHOR]

Precisely interpreting frequency response analysis (FRA) curves is crucial when investigating mechanical malfunctions in power transformer windings (TWs). However, many conventional explanations of FRA features cannot be validated by an equivalent circuit (EC) that represents winding structures using resistance, inductance, and capacitance components in a ladder network. Incorrect interpretation can lead to misdiagnosis and confusion in asset management. Previous ECs are often proposed by analysing winding structures without rigorous verification compared to the corresponding FRA data. The specific EC is acquired using the transfer function (TF) derived from the measured FRA data. This allows for the establishment of the relationship between TW FRA curves, TF equations, and EC topologies. The precise interpretation of FRA curves can be achieved by closely observing the FRA curves created from TFs and ECs. The remarkable similarity between the measured and modelled FRA curves verifies the authenticity of the derived ECs. This significant achievement clarifies many misunderstandings regarding FRA and represents a substantial advancement in FRA technology. [ABSTRACT FROM AUTHOR]

Liquid crystalline polymer (LCP) solutions undergo uniaxial elongation in fiber spinning, yielding highly oriented fibril-structured fibers with enhanced orientation and mechanical properties. This study explores how initial fiber orientation and Frank elasticity influence the dynamics and stability of the isothermal spinning process for LCP solutions. The simplified Larson-Doi mesoscopic model is employed, capable of capturing elastic stress emerging from domain structure evolution. Two main factors, inlet orientation and the Ericksen number as a parameter representing Frank elasticity, significantly affect steady-state fiber orientation profiles and the onset of draw resonance instability, as determined through linear stability analysis. The sensitivity of spinline flow to a sinusoidal disturbance is assessed using the frequency response method. Changes in stability onset concerning these two main factors are reasonably correlated with the extensional behavior of the LCP solution in the spinline and the results of the frequency response. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrated a distributed feedback fiber-laser- (DFB-FL) based ultrasound detection system with a high signal-to-noise ratio (SNR), high sensitivity and wide frequency response range. The DFB-FL was fabricated by UV-inscribing a π phase-shifted grating in the Erbium–Ytterbium co-doped fiber using the phase mask method. The theory of DFB-FL and the sensing principle has been discussed and analyzed. The sensing signal was demodulated via an unbalanced Mach–Zehnder interferometer (MZI) system. The experimental results showed that the sensitivity of the sensor reached 75.18 mV/kPa and the flat frequency response range covered over 30 MHz, which covered the ultrasonic detection frequency range of abnormal discharge in the electric power system. The SNR of this DFB-FL was 42.9 dB, and the corresponding noise-equivalent pressure was calculated as 0.12 kPa. [ABSTRACT FROM AUTHOR]

Frequency response analysis is widely used for the offline diagnosis of winding deformations in power transformers. To apply this approach to a working transformer, the magnitude of the response current needs to be measured by using Rogowski coil sensors across a load current. The saturation of the power frequency magnetic field in these current sensors must be prevented to ensure accurate measurement of such small response currents. Here, a method is presented to suppress the power frequency magnetic field using a sensing system including a special connection of three‐phase current sensors based on the sum of the three‐phase power frequency load currents of the transformer being close to zero. Each sensor comprises two secondary coils: a measuring coil and an anti‐saturation coil. The anti‐saturation coils are connected in parallel with one another through small inductors to eliminate the power frequency magnetic field in the cores of the sensors. Theoretical analysis is used to derive a solution for this system. The experimental results verify the proposed method as enabling the sensors to function with a transformer carrying a load current of 2333 A. [ABSTRACT FROM AUTHOR]

A temporary frequency response test and measurement error prediction method of direct current voltage transformer (DCTV) based on artificial intelligence (AI) is proposed. Firstly, the frequency characteristic of direct current (DC) side voltage of DCTV is analyzed. On this basis, a DCTV transient Frequency Response testing method based on transient alternating current (AC) & DC superposition was developed. Then, the method of voltage sudden change and phase correction is used to achieve transient process DCTV response time testing. Finally, the ant colony optimization (ACO) algorithm was improved by combining an adaptive inertia weight improvement strategy, achieving accurate prediction of the Measurement Error of DCTV. The proposed AI based DCTV transient Frequency Response testing and Measurement Error prediction method were compared and analyzed with the other three methods through simulation experiments. Compared to the other three comparison methods, the maximum transformation error in the evaluation indicators of mean squared error (MSE), root mean squared error (RMSE), and mean absolute error (MAE) decreased by 0.006, 0.0119, and 0.0085, respectively, while the maximum phase error decreased by 0.2794, 0.3004, and 0.2823, respectively. [ABSTRACT FROM AUTHOR]

The frequency response of the photocurrent (Iph) generated in perovskite photodetectors is a crucial issue in imaging or telecommunication applications, although it is briefly discussed in the literature. The present work obtains for the first time the complete expression of the Iph generated on MAPbI3 (MA:methylamoniumI) perovskite polycrystalline thin films. A conditioning circuit is used to extract Iph at 1 V of bias voltage under a square‐modulated laser excitation with a sensitivity smaller than 1 nW and a linear dynamic range LDR > 200 dB; It allows an accurate determination of the module of Iph together with the phase, which is not usually reported in photodetector systems. The frequency domain analysis reveals that Iph can be modeled by two fractional poles located at low (10 kHz) and high (39–250 kHz) cut‐off frequencies. Optimum geometrical parameters and excitation fluence are found for the wider response, resulting for the best device on a cut off frequency up to 250 kHz, and the reproduction of square‐modulated optical waves up to 100 kHz. These results represent an important strategy toward the electrical analysis of MAPbI3 (or other perovskite materials) for the design of posterior electronic stages, optimization of devices and determination of their figures of merit. [ABSTRACT FROM AUTHOR]

This paper envisages studying the features of a conventional inductive ignition system along with its MOSFET and IGBT-based transistorized modifications. The influence of mechanical contact breaker dynamics and ignition coil characteristics on the current and voltage waveforms of the primary and secondary circuits of these studied ignition systems are mathematically and experimentally exposed. The investigation is considered necessary prior to attempting subsequent modeling and diagnostics procedures on the current-voltage performance characteristics of conventional and transistorized ignition systems. The work has demanded the development of an experimental setup based on a basic modifiable ignition system mockup and an instrumentation system to measure and analyze the voltage-current parameters of inductive ignition systems. The paper describes the design details of such instrumentation system, presents mechanical and electrical models for contact breaker and ignition circuits, then simulated to obtain base free-run response waveforms and electrical continuity behavior of the contact. A test of frequency response of the ignition coil provided additional input to the model. An experimental test of continuity of the contact, in agreement with its model, shed light on the actual excitation of the primary coil. The work comments on a sample of the registered current and voltage waveforms in primary and secondary coil windings of the ignition system at atmospheric conditions. Comparisons of waveforms and energy for mechanical contact, MOSFET and IGBT switches are made to establish them as a reference for future tests. [ABSTRACT FROM AUTHOR]

The paper considers an implant of the human inner ear as an electroacoustic system. The implant serves to partially restore human hearing by direct impact on the nerve endings of the coil with electrical impulses. Electrical stimulation of the auditory nerve, in turn, leads to auditory sensations. A block diagram of an implant using an ultrasonic communication line between the external and internal parts of the system is selected. A theoretical study of the influence of parameters on the frequency properties and sensitivity of the ultrasonic line of acoustic information transmission was carried out, which is based on a mathematical algorithm that implements the calculation of the sensitivity of the transmission channel depending on the frequency and channel parameters. A multilayer model of the communication line was chosen for calculations, which contains emitting and receiving piezo plates, two protectors to ensure safe contact between the receiving and emitting piezo plates and bio tissue, an intermediate layer of bio tissue, two dampers that are adjacent to the emitter and receiver, respectively. At the same time, it is considered that the dampers have limited dimensions. As a result, the influence of individual design parameters of the transmission line on the maximum sensitivity of the line and its frequency characteristic is theoretically researched. [ABSTRACT FROM AUTHOR]

Copyright of Zhejiang Electric Power is the property of Zhejiang Electric Power Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Frequency response services are one of the key components used by major electrical networks worldwide, acting to help control the frequency within set boundaries. Battery Energy Storage Systems (BESSs) are commonly deployed for this purpose; however, their potential is limited by susceptibility to cycle-based degradation and widely reported safety incidents. Flywheel Energy Storage Systems (FESSs) do not share these weaknesses and hence could be a potential candidate for longer-term participation in frequency response markets. This study presents the most in-depth and wide-ranging techno-economic analysis of the feasibility of FESSs for frequency response to date. Standalone FESSs are shown to be economically viable across a range of different specifications, achieving a positive Net Present Value (NPV) under varying economic conditions. At a capital cost of 500 GBP/kW with a discount rate of 4%, a 5C FESS can achieve an NPV of GBP 38,586 as a standalone unit. The complex trade-offs when considering hybridising FESSs and BESSs for this application are also investigated in-depth for the first time, again showing positive changes to NPV under various scenarios. Conversely, under some conditions, hybridisation can have a significant negative impact, showcasing the optimisation needed when considering hybrid systems. The impact of introducing a hybrid BESS varies from a low of decreasing the NPV of the system by GBP 97,955 to a high of increasing the NPV by GBP 119,621 depending on the configuration chosen. This comprehensive work provides the foundations for future research into FESS deployment for frequency response services and shows for the first time the circumstances under which deployment for this application would be both technically and economically viable. [ABSTRACT FROM AUTHOR]

Period-permanent-magnet (PPM) electromagnetic acoustic transducer (EMAT) has been widely used in shear horizontal (SH) ultrasonic guided wave testing owing to its advantages, such as non-contact coupling, and convenient to excite SH waves. However, its poor transduction efficiency leads to weak signals and limits the lift-off performance. This article investigates how to improve the signal amplitude by adjusting the number of turns of the racetrack coil. The inductive coupling process of the PPM-EMAT receiver is first studied using the equivalent circuit method, and the corresponding equivalent model is obtained. Aiming at the effects of coil configurations, the equivalent impedance parameters of multilayer racetrack coils are analyzed by calculations and measurements. The proposed model can be used to predict the receiving frequency response of PPM-EMAT receivers with different coil structures, and it has been verified experimentally. It can be obtained that by choosing an appropriate coil configuration and matching resistance, the SH wave signal amplitude can be increased by 3 times. [ABSTRACT FROM AUTHOR]

Molecular communication (MC) is a concept in communication engineering, where diffusive molecules are used to transmit information between nano or micro-scale chemical reaction systems. Engineering MC to control the reaction systems in cells is expected for many applications such as targeted drug delivery and biocomputing. Toward control of the reaction systems as desired via MC, it is important to transmit signals without distortion by MC since the reaction systems are often triggered depending on the concentration of signaling molecules arriving at the cells. In this paper, we propose a method to analyze signal distortion caused by diffusion-based MC channels using frequency response of channels. The proposed method provides indices that quantitatively evaluate the magnitude of distortion and shows parameter conditions of MC channels that suppress signal distortion. Using the proposed method, we demonstrate the design procedure of specific MC channels that satisfy given specifications. Finally, the roles of MC channels in nature are discussed from the perspective of signal distortion. [ABSTRACT FROM AUTHOR]

Offshore wind farms are becoming increasingly distant from onshore centralized control centers, and the communication delays between them inevitably introduce time delays in the measurement signal of the primary frequency control. This causes a deterioration in the performance of the primary frequency control and, in some cases, may even result in frequency instability within the power system. Therefore, a frequency response model that incorporates communication delays was established for power systems that integrate offshore wind power. The Padé approximation was used to model the time delays, and a linearized frequency response model of the power system was derived to investigate the frequency stability under different time delays. The influences of the wind power proportion and frequency control parameters on the system frequency stability were explored. In addition, a Smith delay compensation control strategy was devised to mitigate the effects of communication delays on the system frequency dynamics. Finally, a power system incorporating offshore wind power was constructed using the MATLAB/Simulink platform. The simulation results demonstrate the effectiveness and robustness of the proposed delay compensation control strategy. [ABSTRACT FROM AUTHOR]

This paper discusses N-order bandpass filter (BPF) with all mixed couplings between adjacent resonators, and between end resonators and loads. It has (2N + 1) transmission zeros (TZ) at real frequencies. To the existing (N + 1) TZs generated by mixed couplings, another N TZs are added, which generated by resonators with special properties. Each such resonator is a λ/4 resonator, in which the connection point is located relatively close to the short-circuited end. In this case, the input admittance of the resonator Y(jω) has a pole ωp, which is located to the right and at a small distance from the main resonant frequency ω0. This pole ωp of the Y(jω) function leads to the appearance of a right-handed TZ in a BPF characteristic. If we use N resonators with different connection points, then N additional TZs will appear. The design of that BPF is considered. The measured and simulated frequency responses of the second-order BPF with 5 TZs are presented. [ABSTRACT FROM AUTHOR]

Aluminium and aluminium alloy MMCs (AAMMCs) tend to be the most explored materials in MMC development due to their broad range of properties such as wear resistance, light weight, strength with durability, and improved damping capabilities for automobiles, aerospace, and marine at reasonable production costs among other materials. However, the reinforcements chosen will have an impact on the properties of the composite, bridging the gap between the research problem and the desired specialised application. In that effort, numerous researchers have subsequently explored the influence of AAMMCs with various reinforcements aimed at increasing damping properties. In this work, MMCs alloy as matrix and copper particles as reinforcement sat 0 to 15% were synthesised using stir casting route. MMCs/Cu MMC samples were then investigated using SEM to ensure the dispersion of Cu particles in MMCS MMC before being exposed to a frequency response function to determine the modal frequencies and damping ratios. The acquired results on the influence of Cu particles in MMCs matrix on frequency responses and damping ratios were clearly presented. [ABSTRACT FROM AUTHOR]

InGaN/GaN green micro‐light‐emitting diode (micro‐LED, μLED) arrays with varying device sizes down to 4 μm are fabricated and characterized. The size effects on current‐voltage and capacitance‐voltage characteristics are analyzed showing minimal sidewall effects only at low bias. The influence of pulse modulation frequency on luminance is also characterized and the effect of diode negative capacitance is discussed. Subsequently, a universal and comprehensive compact model for μLEDs are built based on these findings, which covers the capacitance frequency dispersion and size scaling effects. This work reveals the significance of frequency in the display driving strategy and provides design enablement for μLED micro‐display applications including augmented/mixed reality (AR/MR). [ABSTRACT FROM AUTHOR]

Battery energy storage systems (BESS) have emerged as a critical component in maintaining power system stability through frequency regulation. Their rapid response and flexible characteristics have generated considerable interest among researchers. This study focuses on the provision of a fast frequency response service, known as Dynamic Containment Frequency Response (DCFR), in Great Britain (GB). It conducts a detailed assessment of BESS-based DCFR service for frequency regulation and State-of-charge (SOC) management, including the configuration constraints set out by the energy recovery rules and SOC management impact. A methodology is presented to investigate the performance of DCFR-based BESS in a power system, alongside a stability analysis focusing on the impact of the SOC management mechanism. The stability study investigates the potential influential factors of battery SOC management when providing DCFR via root locus. For simulation case studies, a power imbalance estimation method is utilized for gaining the input. Based on the stability analysis results, key BESS configuration parameters are examined in an integrated power system model: C-rate, SOC management range, ratio and target. Another influential factor, SOC management time delay, is also analyzed. Finally, a comparison between DCFR and the previous frequency regulation service, Enhanced Frequency Response (EFR), is conducted. The study reveals that improper SOC management in DCFR can lead to SOC oscillation, adversely affecting performance. However, with proper configuration, DCFR offers more favorable outcomes than EFR in terms of frequency quality, SOC levels, and battery degradation.