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The easy-plane FeSi3.5 composite with excellent magnetic properties and power loss is proposed. The magnetic properties and power loss of the easy-plane FeSi3.5 composite are studied by using the none easy-plane FeSi3.5 composite as a control. This easy-plane FeSi3.5 composite has an initial permeability of 62, resonance frequencies of 100 MHz and 1.5 GHz, and frequency stability of 40 MHz. In addition, the easy-plane FeSi3.5 composite has also excellent loss properties, with a high-frequency power loss of only 108.12 kW/m3. The three kinds of power loss of the easy-plane FeSi3.5 composite are reduced compared with the none easy-plane FeSi3.5 composite through loss separation, especially the eddy current loss and the excess loss. The eddy current loss and the excess loss of the easy-plane FeSi3.5 composite are only 0.03 and 12.93 kW/m3 at 500 kHz, which reduce by 99.44% and 92% compared with the none easy-plane FeSi3.5 composite. Effective reduction of power loss and significant improvement of magnetic properties are important for solving the problem of power loss encountered by power electronic devices at the kHz band. Therefore, the application of the easy-plane FeSi3.5 composite with excellent power loss and high-frequency magnetic properties becomes a novel approach to meet the practical application of power electronics. The method that increases the working frequency and decreases the maximum magnetic flux density keeping the energy transformation efficiency constant is a new method to reduce power loss at the wide frequency band. [ABSTRACT FROM AUTHOR]

K 0.5 Na 0.5 NbO 3 (KNN)-based ceramics with large polarization (P max) and submicron grain size are considered as promising candidates for dielectric capacitors. However, the existence of significant remnant polarization (P r) imposes constraints on achieving high recoverable energy storage density (W rec) and efficiency (η). In this study, we developed and produced ceramic materials by utilizing the composition of (1- x)K 0.5 Na 0.5 NbO 3 - x Bi(Mg 0.5 Hf 0.5)O 3 ((1- x)KNN- x BMH, x = 0–0.22), employing a viscous polymer rolling technique. We utilized a combined strategy to improve the energy storage capabilities of these materials by manipulating their crystal structures, inducing relaxor behavior, and minimizing microdefects. As a result, we obtained an optimum W rec of 3.32 J/cm3 and η of 85.37 % at an electric field strength of 350 kV/cm in the x = 0.18 ceramic. Furthermore, excellent temperature stability was observed within the temperature range 20–120 °C, along with frequency stability across frequencies between 5 and 500 Hz. Moreover, at 200 kV/cm in the same composition (i.e., 0.82KNN-0.18BMH), we obtained a power density value as high as 103.13 MW/cm3, accompanied by a fast discharge speed reaching 30.6 ns. Overall, our results demonstrate that the comprehensive energy storage performances exhibited by the 0.82KNN-0.18BMH ceramic make it highly promising for applications in pulsed-power supply. [ABSTRACT FROM AUTHOR]

As the proportion of renewable energy and power electronics equipment continues to rise, the level of rotational inertia decreases considerably, resulting in severe frequency stability challenges to the power grid. It is of great significance to accurately predict the frequency nadir following a large disturbance. This paper proposes a novel data-model fusion-driven approach for the prediction of frequency nadir. As the physics-driven part, a Simplified Prediction Model (SPM) based on power-frequency polynomial fitting is developed to quickly produce the frequency nadir. As the data-driven part, Back Propagation Neural Network (BPNN) is deployed to correct the errors of the SPM to achieve more accurate results. This serial integration scheme not only obtains the final prediction result with higher accuracy, but also meets the computational efficiency requirements of online prediction. Compared with existing integration-driven methods, SPM only focuses on the active power-frequency characteristics of the system, which retains the most critical effects and greatly reduces the dependence of BPNN on sample data quality. Case studies on a modified IEEE 39-bus system verify the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

The stability and reliability of modern power systems, especially those with several renewable energy sources, strongly rely on load frequency control (LFC) and automatic voltage regulation (AVR) for frequency and voltage control under inconstant load demands. In this study, a new cascade tilt integral derivative-fractional order proportional tilt integral derivative (TID-FOPTID) controller is presented that is polished through the salp swarm algorithm (SSA) for LFC of a multi-area power system with AVR in all control areas. The system integrates capacitive energy storage (CES) and deals with governor dead-band and generation rate constraint nonlinear effects in a thermal-hydro-gas three-area multi-source power system (TAMSPS). The analysis of results, due to the SSA-based TID-FOPTID controller compared to TID-FOTID and TID-FOTID + 1 shows a positive outcome. Integrating CES brings additional improvement in the system performance, the overshoot/undershoot, and settling time are minimized. Finally, the sensitivity analysis reveals that the suggested controller will be effective and reliable for enhancing the frequency stability of the complex power system with a high RES integration level. [ABSTRACT FROM AUTHOR]

Integrating electrolyzers into power systems can significantly contribute to sustainable energy via the generation of green hydrogen while also enhancing frequency stability through effective regulation of the electrolyzers' operating power. This study gives a comprehensive analysis of large-scale electrolyzer plants when providing frequency support to power systems. First, the authors present a model predictive control (MPC)-based secondary frequency controller, combined with a droop controller as the primary frequency controller and a virtual inertia controller. Additionally, the study introduces a universal system frequency response (U-SFR) modeling approach that enables high accuracy, low computation burden, and reduced initial parameters as a testbed. Finally, an in-depth analysis is conducted, focusing on different technical aspects of large-scale electrolyzer plants when providing frequency support services. Case studies integrating PEM and Alkaline electrolyzers into the modified IEEE 39-bus system with over 50% wind power penetration are conducted. It is found that the proposed U-SFR model achieves high accuracy with lower computational time compared to detailed physical models. Additionally, model predictive controllers improve frequency quality more effectively than PID and PID-FLC methods. PEM electrolyzers are found to be more efficient in providing grid frequency support than alkaline electrolyzers due to their technical characteristics. Finally, smaller hydrogen tanks may frequently breach storage constraints, negatively impacting the system's frequency response capability. • Universal system frequency response model with high accuracy and low computation time. • Model Predictive Controller for large-scale PEM and Alkaline electrolyzer plants. • Modified IEEE-39 bus system with 50% wind energy penetration as a testbed. • Technical analysis of PEM and Alkaline electrolyzers on frequency regulation capability. [ABSTRACT FROM AUTHOR]

The emergence of high-entropy perovskite materials provides a new research idea to solve the problem of high remnant polarization and low recoverable energy storage density (W rec) of relaxor ferroelectrics. In this study, barium-based high-entropy perovskite oxides Ba(Zr 0.2 Sn 0.2 Hf 0.2 Nb 0.2 Ti 0.2)O 3 (BZSHNT) were introduced into the 0.94Na 0.5 Bi 0.5 TiO 3 -0.06BaTiO 3 (BNT-6BT) ceramic by the conventional solid state sintering method. The 0.2BZSHNT doped BNT-6BT ceramic demonstrates significantly improved W rec of 3.57 J/cm3 and a high efficiency of 81.6 % compared to those of the BNT-6BT ceramic, which is only 0.5 J/cm3 and 60 % respectively. The doped BZSHNT refines the hysteresis loops and drastically reduces the remnant polarization, which lead to the increase of the polarization difference. The 0.8(BNT-6BT)-0.2BZSHNT ceramics show high discharge energy density, good temperature stability (25–200 °C), excellent frequency stability (10–300 Hz) and superior discharge rate (t 0.9 = 83 ns) because of its increased TiO 6 lattice distortion, atomic disorder, relaxation degree and band gap, as well as the disruption of the long-range ordered ferroelectric domains. Our findings make BNT-6BT doped BZSHNT based ceramics one of the most promising lead-free dielectric energy storage candidates. [ABSTRACT FROM AUTHOR]

The time of a satellite navigation system is primarily generated by the main control station of the ground system. Consequently, when ground stations fail, there is a risk to the continuous provision of time services to the equipment and users. Furthermore, the anticipated launch of additional satellites will further strain the satellite–ground link. Next-generation satellite navigation systems will rely on time deviation measurements from inter-satellite links to independently establish and maintain a space-based time reference, enhancing the system's reliability and robustness. The increasing number of low-Earth-orbit satellite navigation constellations provides ample resources for establishing a space-based time reference. However, this also introduces challenges, including extensive time scale computations, increased link noise, and low clock resource utilization. To address these issues, this paper proposes a Distributed Kalman Plus Weight (D-KPW) algorithm, which combines the benefits of Kalman filtering and the weighted average algorithm, balancing the performance with computational resources. Furthermore, an adaptive clock control algorithm, D-KPW (Control), is developed to account for both the short-term and long-term frequency stability of the time reference. The experimental results demonstrate that the frequency stability of the time reference established by the D-KPW (Control) algorithm reaches 7.40 × 10 − 15 and 2.30 × 10 − 15 for sampling intervals of 1000 s and 1,000,000 s, respectively, outperforming traditional algorithms such as ALGOS. The 20-day prediction error of the time reference is 1.55 ns. Compared to traditional algorithms such as AT1, ALGOS, Kalman, and D-KPW, the accuracy improves by 65%, 65%, 66%, and 67%, respectively. [ABSTRACT FROM AUTHOR]

The BeiDou Navigation Satellite System (BDS-3) has officially provided services worldwide since July 2020. BDS-3 has added new signals for B1C, B2a and B2b based on old BDS-2 B1I and B3I signals, which brings opportunities for achieving high-precision time transfer. In this research, the BDS-3/BDS-2 combined penta-frequency common-view (CV) single-differenced (SD) precise time transfer model is established with B1I, B3I, B2I, B1C, B2a and B2b signals, including dual-, triple-, quad- and penta-frequency (abbreviated as DF, TF, QF and PF) ionosphere-free (IF) combination CV SD models. Taking four long baseline time links (from 637.6 km to 1331.6 km) as examples, the accuracy and frequency stability of the BDS-3/BDS-2 combined DF, TF, QF and PF SD time transfer models were evaluated. The experimental results show that the frequency stability of the TF, QF and PF SD models were improved by 2.5%, 5.3% and 8.5%, on average, over the DF SD model. Compared with the traditional DF (B1I/B3I IF combination) SD model, the standard deviation (STD) of the multi-frequency SD model was reduced by 5.9%, on average, and the frequency stability was improved by 4.0% on average, which had the most apparent effect on the improvement of short-term frequency stability. Specifically, the DF1 (B1C and B2a DF IF combination), TF1 (B1C, B2a and B2b TF IF combination), QF1 (B1C, B1I, B2a and B2b QF IF combination) and PF4 (B1C, B1I, B2a, B2b and B3I PF IF combination) SD models had better performance in timing, and the PF4 SD model had the best performance. Considering that the PF4 (one PF signal IF combination) SD model does not require an estimated inter-frequency bias and that its noise factor is minor compared with the PF1 (four DF signal IF combination), PF2 (three TF signal IF combination) and PF3 (two QF signal IF combination) SD models, we recommend the PF4 SD model for multi-frequency time transfer and the use of the PF2, PF2 or PF3 SD model to supplement the PF4 SD model in cases of penta-frequency observation loss. [ABSTRACT FROM AUTHOR]

With the popularity of renewable energy sources, fault‐tolerant frequency stability of distributed generation systems has become a major challenge. This paper proposes an optimal frequency fault‐tolerant control method in the distributed generation system, utilizing adaptive dynamic programming combined with fuzzy critic estimation. First, based on the operational state of the system, a non‐linear dynamic model for the virtual synchronous generator is established. Then, considering the occurrence of actuator faults, the fault‐tolerant control problem is formulated as an optimal control problem, where a fault observer is designed to estimate the fault signals. Furthermore, the proposed adaptive dynamic programming method based on fuzzy critic estimation is employed to effectively solve the highly coupled nonlinear Hamilton–Jacobi–Bellman equation and ensure the state convergence of the system with uniform ultimate boundedness. The optimal fault‐tolerant control law ensures a bounded frequency error for the virtual synchronous generator system in the event of faults. Finally, the effectiveness of the optimal control method is verified by two sets of simulations. [ABSTRACT FROM AUTHOR]

Rockfall represents one of the most destructive geomorphic processes for infrastructure and settlements located at the foot of mountain slopes. Furthermore, it poses a hazard for visitors and hikers. Despite the high anthropic activity in these environments, research on the reconstruction of rockfall in the high mountains of Mexico is still scarce. We used dendrochronological, dendrogeomorphological and lichenometric approaches to study the age and rockfall dynamics in a talus slope in central Mexico. Tree- ring chronologies were constructed from 140 samples of 50 Pinus hartwegii trees, 10 Juniperus monticola shrubs and 16 Ribes ciliatum shrubs to determine the age, frequency and rockfall stability at the upper limit of the forest (~4000 m a.s.l.). 52% of the tree samples showed impact scars, 39% callus tissue, 7% growth suppression and 2% corresponded to trees killed by rockfall. The frequency of rockfalls has increased since the second half of the 20th century, with the 1990s being the period of greatest activity. The years with the greatest disturbance were 1991, 1994 and 1998, possibly due to the intense rainfall that accumulated during the summer, as well as the earthquakes recorded in central and southern Mexico with magnitudes ⩾6. For the lichenometric analysis, 231 thalli of Rhizocarpon geographicum were measured in an active rockfall area. The results suggested three areas of rockfall activity. In the first area the ages were from 61 (±5 year) to 322 years (±41 year). In the second area, the ages were from 12 (±3 year) to 50 years (±12 year). The third area corresponds to an active zone with lichen-free blocks, located near the escarpment. The combination of dendrochronological and lichenometric methods allows a better determination of the minimum ages of rockfall, frequency, spatial distribution, and their possible factor triggers. [ABSTRACT FROM AUTHOR]

Dielectric capacitors play an increasingly important role in modern electronic power systems due to their ultrahigh charging and discharging speeds and power density. Much research has focused on enhancing dielectric breakdown strength to achieve better energy storage performance; however, this increases the potential for heat generation and unexpected insulation failures, thereby affecting the stability and lifespan of devices. This study introduces a small amount of Na+ dopants at the A-site of BaTiO 3 , inducing lattice distortions and enhancing local polarization to increase energy storage density rather than through enhancing breakdown strength. The introduction of Na+ enhances the ferroelectric properties, with polar nano-regions (PNRs) gradually evolving into long-range ordered large domains. In the Ba 0.985 Na 0.015 TiO 3 films, the coexistence and coupling of abundant PNRs with a few long-range ordered ferroelectric domains result in high saturation polarization and low residual polarization. At a moderate electric field of 2.3 MV cm−1, an ultrahigh energy density of 44.3 J cm−3 and a high energy storage efficiency of 78.6 % were obtained. Additionally, the film exhibits excellent frequency stability (100 Hz-20 kHz), temperature stability (30–180 °C), fatigue resistance (107 cycles), and high pulsed discharge energy density, along with great thermal stability. This work provides new insights into achieving exceptional energy storage performance in single-phase films. [ABSTRACT FROM AUTHOR]

Microfluidic chips are considered to be one of the main controllers for future pneumatic flexible actuators. An oscillator is the most direct way to generate a pressure cycle signal, which drives an actuator to reciprocate. Based on the principle of a fluid equivalent circuit and membrane microvalve structure, the working characteristics of a microfluidic single-gate oscillator are described in this paper. This device can produce an oscillation pressure signal at frequencies over 80 Hz with a certain frequency stability. The results show that the operating characteristics of the oscillator are affected by the flow resistance, air cavity and input pressure. This research also provides a new potential application method for robot control in environments unfriendly to electronic devices, such as strong electric fields, strong magnetic fields and underwater environments. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press 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.)

A 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 H2$\mathcal {H}_2$‐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 26%$26\%$ 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 77.1%$77.1\%$. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

NaNbO3 (NN)‐based materials have attracted widespread attention due to their advanced energy storage performance and eco‐friendliness. However, achieving high recoverable energy storage densities (Wrec) and efficiency (η) typically requires ultrahigh electric fields (E > 300 kV/cm), which can limit practical use. In this work, we present a synergistic strategy that employs the ferroelectric material Bi0.5Na0.5TiO3 (BNT) to augment the Pmax and the linear material Bi0.2Sr0.7TiO3 (BST) to optimize the P–E loops. Furthermore, a two‐step sintering process is implemented to preserve high Pmax values under lower electric field. As a result, ternary (1−x)(0.90NN‐0.10BNT)‐xBST was successfully prepared, achieving a high Wrec of 5.1 J/cm3 and a η of 85% in x = 0.20 samples at a low electric field of 290 kV/cm. Moreover, the x = 0.20 samples showed good frequency stability (1–200 Hz) and temperature stability (27°C–100°C). These results provide guidance for the development of ceramics with high energy storage properties under low electric fields. [ABSTRACT FROM AUTHOR]

This research presents the development and construction of a cost-effective instrument, designed to measure the dielectric constant of liquids by employing a non-contact method that relies on determining the capacitance of a cell containing the liquid and its relaxation frequency. This instrument utilizes an astable multi-vibrator integrated with a resistance–capacitor network, in which the cell housing the liquid of interest functions as a capacitor element of the oscillator. The frequency of the generated oscillations is meticulously recorded using a seven-digit frequency meter with a resolution of 1 Hz. The cell was filled with an array of pure liquids with known dielectric constants, and their frequencies were subsequently recorded at ambient temperatures. An equation was fitted to the frequency–dielectric constant curve, which was used as a calibration equation to determine the dielectric constant of subsequent liquids. In addition to pure liquids, dielectric constants for solvent mixtures of varying mole fractions were also calculated using the previously established calibration equation. Our results demonstrated excellent frequency stability of the instrument, and the obtained dielectric constant values displayed significant consistency with both the experimental data and predictions made by computational methodologies. This suggests that the constructed instrument exhibits a high level of accuracy in measuring the dielectric constant of both pure and mixed liquids, establishing its potential utility in relevant research and industrial applications. [ABSTRACT FROM AUTHOR]

In this paper, a rolling planning model for high proportion renewable energy generation power systems is proposed, considering frequency security constraints, to address the frequency stability challenges posed by increased integration of wind and solar energy into the power grid under the "double carbon" goal. First, this study establishes a frequency response model for a thermal generation unit (TGU) and analyzes the impact of the high proportion of renewable energy on system frequency stability. Subsequently, a dynamic frequency security constraint is formulated, which can be used in generation planning to address the frequency issues. Second, a bi-level rolling planning model for high proportion renewable energy generation power systems considering dynamic frequency security constraints is established. The upper level focuses on investment decisions. The lower level incorporates frequency security constraints into the operational simulation to guarantee the frequency stability of the power system when making decisions on the size of newly built TGUs annually. Finally, case studies are conducted to demonstrate the validity and effectiveness of the proposed rolling planning model. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to improve the seal performance by proper design of the cavity shape of the damping holes, especially the rotordynamics characteristics of the hole-pattern damped seal (HPDS). Design/methodology/approach: A new damping seal structure that comprises a circle-shaped cavity and two directional leaf-shaped cavities with a dovetail-shaped diversion groove is proposed. The comparative study on the sealing characteristics of dovetail-shape, leaf-shape and classical circular HPDSs was carried out using ANSYS CFX. Findings: The dovetail-shaped HPDS significantly outperformed two other damping seal designs in leakage and rotordynamic performance. At a rotating speed of 7,500 rpm, it showed a 25% reduction in leakage, a 23% increase in average effective damping and a 119% increase in average effective stiffness. The cross-coupled stiffness Kxy shifted from positive to negative, reducing circumferential flow. The dovetail's inclined leaf-shaped grooves create a double vortex that slows jet velocity in the seal clearance and alters spiral flow direction, resulting in a uniform pressure distribution and enhanced rotor stability at low frequencies. Originality/value: This study proposes a novel HPDS with dovetail-shaped diversion grooves. The seal can realize the simultaneous improvement of rotordynamics and leakage characteristics compared to the current seal structure. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2024-0127/ [ABSTRACT FROM AUTHOR]

This study develops a new class of Euler-buckled beam based nonlinear energy sink (EBNES) with three configurations, which is expected to attenuate the disturbance effects and further enhance vibration suppression under launching and on-orbit loads simultaneously. The effects of different arrangements on amplitude-frequency responses of the primary system are derived and analyzed through complexification-averaging method, and the approximate solutions are verified by fourth-order Runge Kutta method. Comparison results exhibit that the EBNES-I is much more effective with enhanced vibration reduction performance and stability in a broad frequency range. Furthermore, a two-degree-of-freedom dynamic model of the flywheel system, which integrates the EBNES-I and the supporting structure in satellite, is established. The vibration reduction and bifurcation behaviors of the proposed EBNES-I are investigated, and the efficiency of the proposed EBNES-I in vibration reduction of the flywheel is compared to that of a traditional cubic-stiffness-type NES. It is found that the EBNES-I exhibits a good vibration reduction performance on the dynamic responses of the flywheel system in launching and on-orbit stage simultaneously. Additionally, the bifurcations of the coupled system are studied in order to investigate the influences of gravity and excitation amplitudes on the stability of the EBNES. Calculation results provide conditions for occurrence of the saddle-node (SN) and Hopf bifurcations. [ABSTRACT FROM AUTHOR]

This paper proposes goal-function-based decentralized control of microgrids. In addition to being an instrument for maintaining the grid voltage and frequency stability, each grid-tie inverter generates a current component with the aim of compensating for voltage distortion in the node where it is connected. The designed goal-function does not need to rely on the assumption that a microgrid is dominantly inductive or resistive to derive its control law, as is mostly the case with the droop-based approach. The priorities of the proposed scheme can be adjusted according to user preferences. In addition, the control algorithm is independent of network topology, can be applied in both islanded and non-islanded microgrids, and secure system scalability. The proposed method is verified by detailed simulations. [ABSTRACT FROM AUTHOR]

Capacitive power transfer (CPT) is a technology that is emerging as an alternative to inductive power transfer (IPT) in applications requiring low to medium power. A great interest has been developed in the implementation of CPT systems in battery charging systems, where a condition to compete with IPT systems is the need to increase the power transfer in the CPT systems without significant losses. This paper puts forth a design methodology for a stabilizing network, which has been applied to a CPT system. This methodology has been developed through impedance analysis of the circuit, in order to achieve maximum power transfer, with total gains of voltage and current reaching a value close to unity. The methodology allows for the calculation of the value of the components of the stabilizing network, which has been designed with the objective of stabilizing the resonant frequency against changes in the capacitance of the transmission plates. To validate the design procedure, an experimental prototype was developed at 25 W and an operational frequency of 1.55 MHz. The results obtained validate the design methodology. [ABSTRACT FROM AUTHOR]

Proportion Integration Differentiation (PID) is a common clock disciplining algorithm. In satellite clock source equipment and in Internet of Things (IoT) sensor nodes it is usually required that both time and frequency signals have high accuracy. Because the traditional PID clock disciplining method used in the equipment only performs PID calculation and feedback control on single variable, such as frequency, the time accuracy error of the clock source is large and even has inherent deviation. By using the integral relationship between frequency and time, a new two variables PID control algorithm for high-precision clock disciplining is proposed in this paper. Time is taken as the constraint variable to make the time deviation converge. It can guarantee a high accuracy of time and high long-term stability of frequency. At the same time, frequency is taken as the feedback variable to make frequency obtain fast convergence. It can ensure high short-term stability of the frequency and the continuity of time. So, it can make the time and frequency of the disciplined clock have high accuracy and stability at the same time. In order to verify the effectiveness of the proposed algorithm, it is simulated based on the GNSS disciplined clock model. The GNSS time after Kalman filtering is used as the time reference to discipline the local clock. The simulation results show that the time deviation range of a local clock after convergence is −0.38 ns∼0.31 ns, the frequency accuracy is better than 1 × 10 − 15 averaging over one day, and the long-term time stability (TDEV) for a day is about 7 ps when using the two variables PID algorithm. Compared with the single variable PID algorithm, the time accuracy of the two variables PID algorithm is improved by about one order of magnitude and the long-term time stability (TDEV) is improved by about two orders of magnitude. The research results indicate that the two variables PID control algorithm has great application potential for the development of clock source equipment and other bivariate disciplining scenarios. [ABSTRACT FROM AUTHOR]

In power system, stability analysis becomes important to identify the level of stability and security of electrical power systems. This article proposes a flexible alternating current systems-unified power flow compensator (FACTS-UPQC) compensator installed in the high-voltage network to ensure stability of voltage and frequency in the power grid facing voltage dips, over-voltage and short-circuit faults. Thus, an artificial intelligence algorithm based on fuzzy logic method is implemented to have the appropriate values of FACTS-UPQC conditioner. The voltage stability improvement is demonstrated by the variation margin of amplitude and phase angle. Frequency stability aims to obtain a frequency within a minimal variation. A 14-bus test electrical system is modeled to implement the advanced control strategy. MATLAB/Simulink software is used to prove the functionality of the method in improving the stability of power system. The simulation results showed a reduction of harmonic distortion rate (HDR) and a minimization of the voltage variation range for the implemented fuzzy logic system compared with the literature. [ABSTRACT FROM AUTHOR]

Classical frequency-stabilized lasers have achieved high-frequency stability and reproducibility; however, their extensive wavelength spacing limits their utility in various scenarios. This study introduces a novel frequency-stabilized laser scheme that integrates a Fabry-Perot etalon (FPE) with digital control technology and wavelength modulation techniques. The FPE, characterized by multiple transmission peaks at minimal frequency intervals, provides stable frequency references for different lasers, thereby enhancing the system's flexibility and adaptability. An error signal is derived from the first-order differentiation of the FPE's transmission curve. A 180° phase difference was observed in the feedback output signal when the laser's central frequency diverged from the reference, determining that the direction of the frequency control was accordingly determined.Employing feedback control, the laser's output frequency is stabilized at the transmission peak frequency of the FPE. Experimental results demonstrate that this stabilization scheme effectively locks the laser's output wavelength to different transmission peak frequencies of the FPE, achieving 25 GHz wavelength spacing. The frequency stability is improved by two orders of magnitude on a second-level timescale, maintained within hundreds of kHz, equating to a frequency stability level of 10−10. [ABSTRACT FROM AUTHOR]

According to General Relativity Theory (GRT), by comparing the frequencies between two precise clocks at two different stations, the gravity potential (geopotential) difference between the two stations can be determined due to the gravity frequency shift effect. Here, we conduct a clock-transportation experiment for measuring geopotential differences based on frequency comparisons via satellite links between two remote hydrogen atomic clocks. Based on the net frequency shift between the two clocks in two different periods, the geopotential difference between stations of the Beijing 203 Institute Laboratory (BIL) and Luojiashan Time-frequency Station (LTS) is determined. Comparisons show that the experimental result deviated from the reference of Earth gravity model EGM2008 result by (38.5 $ \pm $ ± 45.9) m in Orthometric Height (OH). The results are consistent with the frequency stabilities of the hydrogen clocks (at the level of ${10^{ - 15}}$ 10 − 15 ) used in the experiment. With the rapid development of time and frequency science and technology, the approach discussed in this study for measuring the geopotential is prospective and thus, could have broad applications. [ABSTRACT FROM AUTHOR]

Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press 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.)

Copyright of Journal of Shanghai Jiao Tong University (1006-2467) is the property of Journal of Shanghai Jiao Tong University 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.)

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny 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.)

Soft magnetic composites (SMCs) are key materials in electronic devices. Conventional SMCs incorporate too much insulating material in order to reduce eddy current loss at high frequency, resulting in severe magnetic dilution and demagnetization field, which leads to deterioration of the magnetic performance. In this paper, ZnO precursor is homogeneously deployed on the surface of FeSiAl, which in situ generates a thin and dense Al2O3 layer on the surface of FeSiAl through the interfacial solid phase reaction between Al and O atoms during annealing process. Meanwhile, ferromagnetic ZnO layer is simultaneously obtained due to the loss of O. The formed Al2O3/ZnO layers effectively reduce power loss and endow high frequency stability with less influence on effective permeability. Finally, FeSiAl/ZnO‐0.4% SMC exhibits low power loss of 83.2 mW cm−3 (50 mT/100 kHz), high effective permeability of 92, and cut‐off frequency as high as 40 MHz. This study provides an efficient route for high performance SMCs and broadens high frequency application of soft magnetic devices. [ABSTRACT FROM AUTHOR]

In this paper, we embark on a captivating exploration of the stabilization of locally transmitted problems within the realm of two interconnected wave systems. To begin, we wield the formidable Arendt-Batty criteria (Trans. Am. Math. Soc. 306(2) (1988) 837–852) to affirm the resolute stability of our system. Then, with an artful fusion of a frequency domain approach and the multiplier method, we unveil the exquisite phenomenon of exponential stability, a phenomenon that manifests when the waves of the second system synchronize their propagation speeds. In cases where these speeds diverge, our investigation reveals a graceful decay of our system’s energy, elegantly characterized by a polynomial decline at a rate of t − 1 . [ABSTRACT FROM AUTHOR]

The transmission end of large-scale wind power generation bases faces challenges such as high AC-DC coupling strength, low system inertia, and weak voltage support capabilities. Deploying distributed synchronous condensers (SCs) within and around wind farms can effectively provide transient reactive power support, enhance grid system inertia at the transmission end, and improve dynamic frequency support capabilities. However, the high investment and maintenance costs of SCs hinder their large-scale deployment, necessitating the investigation of optimal SC configuration strategies at critical nodes in the transmission grid. Initially, a node inertia model was developed to identify weaknesses in dynamic frequency support, and a critical inertia constraint based on node frequency stability was proposed. Subsequently, a multi-timescale reactive power response model was formulated to quantify the impact on short-circuit ratio improvement and transient overvoltage suppression. Finally, a two-stage optimal configuration strategy for distributed SCs at the transmission end was proposed, considering dynamic frequency support and transient voltage stability. In the first stage, the optimal SC configuration aimed to maximize system inertia improvement per unit investment to meet dynamic frequency support requirements. In the second stage, the configuration results from the first stage were adjusted by incorporating constraints for enhancing the multiple renewable short-circuit ratio (MRSCR) and suppressing transient overvoltage. The proposed model was validated using the feeder grid of a large energy base in western China. The results demonstrate that the optimal configuration scheme effectively suppressed transient overvoltage at the generator end and significantly enhanced the system's dynamic frequency support strength. [ABSTRACT FROM AUTHOR]

Current Differencing Buffered Amplifiers (CDBAs) are a critical class of analog circuit components capable of handling both current and voltage signals with minimal power consumption. Due to their low impedance voltage output, they play a significant role in modern electronics for developing high-performance, high-precision analog and mixed-signal circuits. But, designing and characterizing CDBAs pose several challenges, such as ensuring stability at high frequencies, minimizing noise impact for high-precision applications, and enhancing adaptability. Integrating CDBAs with other analog components to create multifunctional integrated circuits opens many opportunities in the analog signal-processing domain. This paper reviews the evolution and applications of CDBAs in analog signal processing. Various implementation schemes, including those using commercial Current Feedback Amplifiers (CFAs) and novel CMOS configurations, are analyzed for their performance metrics such as supply voltage, power dissipation, input/output impedances, and technology node. Future trends and challenges in advancing CDBA technology towards higher integration and lower-voltage operation are discussed, highlighting potential applications in next-generation electronics. [ABSTRACT FROM AUTHOR]

Atoms confined in the optical lattice can be interrogated with Doppler- and recoil-free operation. However, if not properly controlled, the optical lattice may limit clock accuracy. To improve the lattice-light-shift uncertainty, the cooling and trapping lasers' frequency stability is optimized, and the atom's signal stability is enhanced. A ring-cavity Ti:sapphire laser is locked to the optical frequency comb, which is referenced to a 578 nm ultra-stable laser, and the beat note's stability is on the order of 10−16. Using a 10 cm Fabry–Pérot cavity referenced to the Ti:sapphire laser, the optical frequency stability is transferred to the 399 nm cooling laser, creating favorable conditions for evaluating the lattice-light-shift accurately. We reevaluate lattice-light-shift in our 171Yb optical lattice clock with an uncertainty of 8.1 × 10−18, which is an order lower than our previous result, and the magic frequency is determined to be 394 798 266.6(1.3) MHz. [ABSTRACT FROM AUTHOR]

Microgrids (MGs) play a crucial role in modern power distribution systems, particularly in ensuring reliable and efficient energy supply, integrating renewable energy sources, and enhancing grid resilience. Voltage and frequency stability are paramount for MG operation, necessitating advanced control frameworks to regulate key parameters effectively. This research introduces a multilayer interactive control framework tailored for MGs utilizing distributed energy resources (DERs). The framework comprises primary control layers, integrating internal voltage and current controller loops, and secondary layers employing distributed finite‐time control (DFTC) strategies. Through simulation studies and comparative analyses with traditional proportional‐integral (PI) controllers, the effectiveness of DFTC controllers in reducing initial oscillations and improving stability is demonstrated. Major findings include the superior performance of DFTC controllers in stabilizing voltage and frequency parameters, optimizing power output, and enhancing overall operational efficiency. Additionally, insights into the operational dynamics of MG systems highlight the significance of advanced control strategies in mitigating fluctuations and ensuring system stability. Furthermore, the proposed method demonstrates significant efficacy improvements over conventional approaches. Voltage stability is enhanced with oscillation amplitudes less than 0.01 pu, active power control achieves a stable level of 0.93 pu, and frequency fluctuations are reduced to 0.004 Hz and effectively recovered to 0.002 Hz. These improvements suggest that the proposed method enhances system stability and control precision by approximately 95% compared to conventional methods, as it achieves much tighter control over voltage, active power levels, and frequency fluctuations. [ABSTRACT FROM AUTHOR]

In this work, 0.88BaTiO 3 -0.12Bi(Mg 1/2 Ti 1/2)O 3 -xmol% NaNbO 3 (x = 0, 0.5, 1, 1.5, 2) ceramics have been synthesized by using the traditional solid-state route. The effects of NaNbO 3 on the phase structure, microstructure, dielectric, ferroelectric, and energy storage properties of the 0.88BaTiO 3 -0.12Bi(Mg 1/2 Ti 1/2)O 3 ceramics have been studied in detail. The ceramic doped with 1.5 mol% NaNbO 3 exhibited a releasable energy storage density of 2.287 J/cm3, significantly higher than the undoped sample (1.194 J/cm3). The breakdown strength increases from 130 kV/cm for the undoped sample to 210 kV/cm for the sample doped with 1.5mol% NaNbO 3. The enhanced breakdown strength of the 0.88BaTiO 3 -0.12Bi(Mg 1/2 Ti 1/2)O 3 -xmol% NaNbO 3 ceramics is primarily due to NaNbO 3 doping, which produces a wider bandgap, smaller grain size, and higher specific resistance. The 0.88BaTiO 3 -0.12Bi(Mg 1/2 Ti 1/2)O 3 -xmol% NaNbO 3 ceramic's energy storage performance exhibits great temperature stability, frequency stability, and cycle stability at 120 kV/cm. [ABSTRACT FROM AUTHOR]

With the large-scale distributed energy resources (DERs) interfaced by power electronic converters connected to the power grid, the traditional synchronous generation is gradually replaced, and the inertia and primary frequency regulation capability of the power system is weakened, which seriously threatens the frequency security of the power grid. In view of the above problems, a hierarchical control strategy by coordinating the distributed wind turbine (WT) and photovoltaic (PV) is presented to improve the transient frequency (TF) and steady-state frequency (SSF). For the system control level, the optimal frequency regulation coefficients of multiple WTs and PVs clustering systems are determined by the optimal control principle with minimum frequency regulation energy, while considering the constraints of TF and SSF. For the WT/PV control level, the frequency regulation coefficients of WTs and PVs are solved by the model predictive controller (MPC) and alternating direction method of multipliers (ADMM), with the minimum control cost of WT and PV. It achieves the optimal allocation of frequency regulation power and improves the computing efficiency. Finally, the validity of the proposed method is tested in the modified IEEE 10-machine 39-bus system. [ABSTRACT FROM AUTHOR]

The rapidly increasing proportion of renewable energy sources has led to a reduction in the relative share of synchronous units, which has resulted in a decline in the inertia of the power system and a decrease in its voltage support capacity. This has led to several issues related to the frequency and voltage stabilities of the power system. To ensure these frequency and voltage stabilities, it is necessary to maintain a number of synchronous units online in the day-ahead generation schedule. First, the dynamic frequency change process after a power system fault is discussed, and a linear expression is derived for the frequency stability constraints involving energy storage systems and wind turbines. Second, the short-circuit capacity of the bus is characterized to describe the strength of voltage support, and the minimum short-circuit capacity requirement of the bus is solved based on the transient voltage recovery problem after clearance of the short-circuit faults. The total short-circuit capacity provided by the unit to the bus is then calculated through the network reactance matrix to establish the voltage stability constraint. Subsequently, the security-constrained unit commitment model considering frequency and voltage stabilities (FVS-SCUC) is established. Finally, the effectiveness of the proposed model is demonstrated through a numerical simulation of the IEEE-39 system comprising storage and wind turbines. The model ensures the frequency and voltage securities of the system, and the renewable energy output is improved upon considering energy storage. Thus, the overall system cost was reduced by nearly 30% by considering the frequency regulation effects of the energy storage system and wind turbine as well as the voltage regulation effects of the energy storage system. [ABSTRACT FROM AUTHOR]

Low inertia poses a significant challenge to the widespread integration of photovoltaic (PV) systems into the grid, particularly affecting frequency stability. This paper addresses this challenge by proposing an advanced hybrid inertia (AHI) approach, characterized by the integration of real and virtual inertia, combined with the application of intelligent control techniques, to enhance the primary frequency response of a PV system. Internal inertia is provided by a synchronous generator (SG) acting as a compensator, while virtual inertia is generated through a real-time deloading strategy in the PV plant. The AHI is implemented on an isolated grid, utilizing various intelligent control techniques to improve frequency stability. The intelligent techniques employed include genetic algorithms (GA) and fuzzy logic controllers (FLC), which do not require mathematical modeling. This allows them to overcome the nonlinear dynamics of the PV plant and the uncertainties associated with climatic changes. These techniques are applied to the nonlinear components on the generator side, including the governor loop, DC-DC converter loop, and power reserve injection management loop. A frequency fluctuation scenario, induced by generating power perturbations in the proposed system, demonstrates and validates the improvement in frequency stability achieved by the HI and intelligent techniques. All tests are conducted using MATLAB Simulink. Various simulation results show a significant improvement in frequency stability through the incorporation of HI and intelligent control techniques. [ABSTRACT FROM AUTHOR]

In order to solve the problem of frequency modulation power deviation caused by the randomness and fluctuation of wind power outputs, a method of auxiliary wind power frequency modulation capacity allocation based on the data decomposition of a "flywheel + lithium battery" hybrid-energy storage system was proposed. Firstly, the frequency modulation power deviation caused by the uncertainty of wind power is decomposed by the successive variational mode decomposition (SVMD) method, and the mode function is segmented and reconstructed by high and low frequencies. Secondly, a mathematical model is established to maximize the economic benefit of energy storage considering the frequency modulation mileage, and quantum particle swarm optimization is used to solve the target model considering the charging and discharging power of energy storage and the charging state constraints to obtain the optimal hybrid-energy storage configuration. Finally, the simulation results show that, in the step disturbance, the Δfmax of the hybrid-energy storage mode is reduced by 37.9% and 15.3%, respectively, compared with single-energy storage. Under continuous disturbance conditions, compared with the single-energy storage mode, the Δfp_v is reduced by 52.73%, 43.72%, 60.71%, and 47.62%, respectively. The frequency fluctuation range is obviously reduced, and the frequency stability is greatly improved. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to provide an overview of the methodology used to estimate radiation genetic risks and quantify the risk of hereditary effects as outlined in the ICRP Publication 103. It aims to highlight the historical background and development of the doubling dose method for estimating radiation-related genetic risks and its continued use in radiological protection frameworks. Results: This article emphasizes the complexity associated with quantifying the risk of hereditary effects caused by radiation exposure and highlights the need for further clarification and explanation of the calculation method. As scientific knowledge in radiation sciences and human genetics continues to advance in relation to a number of factors including stability of disease frequency, selection pressures, and epigenetic changes, the characterization and quantification of genetic effects still remains a major issue for the radiological protection system of the International Commission on Radiological Protection. Conclusion: Further research and advancements in this field are crucial for enhancing our understanding and addressing the complexities involved in assessing and managing the risks associated with hereditary effects of radiation. [ABSTRACT FROM AUTHOR]

This study employed a stepwise optimization strategy, including doping Sr(Ga 0.5 Nb 0.5)O 3 (SGN) into 0.65Na 0.5 Bi 0.5 TiO 3 -0.35Sr 0.7 Bi 0.2 TiO 3 (NBT-SBT) ceramics to modify the composition and a further processing improvement. By introducing Ga3+ and Nb5+ ions with high ionic polarization rates into the B-site, the average polarization of the unit cell was maintained while further inducing local disordered fields and promoting polar nanoregions. The high activity of the polar nanoregions was confirmed using piezoelectric microscopy. The effective energy storage density (W rec) of 2.73 J/cm³ was obtained when the SGN doping was 6.5 %. Subsequently, the densification of ceramics was improved through viscous polymer processing, thereby enhancing the breakdown strength (BDS). A combined approach of finite element simulation and experimental studies was further utilized to investigate the impact of grain size on the BDS. The stepwise optimization strategy enabled the NBT-SBT-6.5SGN VPP ceramics to achieve the W rec of 5.2 J/cm3 and efficiency (η) of 85 % under 350 kV/cm. Additionally, the ceramics developed by this strategy possess excellent temperature and frequency stability and pulse discharge performance, making them potential candidates for practical applications. [ABSTRACT FROM AUTHOR]

The demand for cost–effective materials for thick film resistors has driven the exploration of alternative functional materials to replace the traditionally used ruthenium oxides. This study investigates the synthesis and properties of copper–substituted La 0.5 Sr 0.5 CoO 3 (La 0.5 Sr 0.5 Co 1-x Cu x O 3 , LSCCu, x = 0.02–0.10) ceramics as a potential economical substitute. The crystal structure, electrical performance, and sintering behavior of LSCCu with varying Cu2+ contents were characterized through solid–state reactions and first–principles simulations. The results indicate that the perovskite structure is maintained with increasing Cu2+, while the densification temperature, crystallinity, and conductivity decrease. Moreover, Cu2+ substitution reduced the DOS across the Fermi level and weakened the electron transport in LSCCu. The sample with x = 0.06 exhibited a promising conductivity of 2609 S/cm after sintering at 1150 °C, comparable to commercial thick film resistor materials. The temperature coefficient of resistance (TCR) of LSCCu showed a metallic behavior with a low value of 1148 ppm/°C for the x = 0.06 sample. Additionally, the LSCCu ceramics possess good long–term stability and frequency stability of resistance. These findings suggest that LSCCu ceramics are a promising economical material for thick film resistor applications. [ABSTRACT FROM AUTHOR]

As the share of renewable energy sources in the power system keeps growing, a new issue with frequency stability – diminishing and changing inertia – has emerged. Estimating power system inertia has received a lot of attention lately in order to market design of synthetic inertia as an additional service and implement timely corrective steps for robust frequency control. Curve fitting technique has emerged as one of the promising techniques for estimation of power system inertia, however, many challenging aspects need to be addressed for its practical applications. This study aims to systematically assess the effectiveness of the curve fitting method under a range of operational parameters and conditions, such as the curve fitting order, the length of data to be used for curve fitting after an event begins, and the length of the moving average filter applied to the frequency data to remove oscillatory and noise from the frequency transient. The simulation studies have been performed on DIgSILENT and MATLAB platforms. The results show that very high and very low order curve fitting results are high errors and the 5th order model with mean error in estimated value of inertia less than 1% has outperformed others. The analysis on various window width of moving average filter found that increasing the window width results in more error. For IEEE-9 bus system, a filter up to 850 ms width has a mean percentage error below 1%. The analysis also revealed that the duration of the data used for curve fitting is not significant. For variation of the duration of the data used for the curve fitting from 50 ms to 500 ms, the estimated inertia values are found to be in a close range of 2.4881 s to 2.5262 s, for the single machine system with H = 2.5 s. The analysis presented in this study will be useful for effective application of curve fitting method in inertia estimation. [ABSTRACT FROM AUTHOR]

The paper deals with the structure of under-frequency load shedding (UFLS) relays in the interconnected power system (IPS) of Ukraine. The equivalent power system model to study the UFLS operation is developed, and UFLS configuration scenarios considering the requirements of ENTSO-E, are configured. The frequency stability for different scenarios of UFLS settings considering planned and emergency active power imbalances are studied. The plots illustrating the frequency change in the power system under these conditions are presented. [ABSTRACT FROM AUTHOR]

As China accelerates its transition to a low-carbon society, its power system is facing growing challenges in terms of maintaining adequacy amid a rapidly evolving energy structure. The concept of adequacy, traditionally focused on power capacity and generation, has broadened to include dimensions like flexibility and inertia. Against this backdrop, optimizing the integration of coal power and renewable energy to meet the system's needs for adequacy, flexibility, and frequency stability has become a critical research area. This paper introduces the concept of "Generalized Adequacy", expanding the traditional understanding of adequacy, and proposes an optimization model for the coordinated development of coal power and renewable energy based on this concept. This study examines the effects of extreme weather, renewable energy penetration, wind–solar ratios, and generalized adequacy constraints using a case study from a central region of China. The findings reveal that extreme weather conditions drive an increase in photovoltaic installations, while higher renewable energy penetration leads to more wind power installations. Accounting for generalized adequacy constraints can moderate the retirement of coal-fired plants, reducing unnecessary inertia support in normal conditions and ensuring dynamic frequency stability during extreme weather events. [ABSTRACT FROM AUTHOR]

Modern power systems are growing in complexity due to the installation of large generators, long transmission lines, the addition of inertialess renewable energy resources (RESs) with zero inertia, etc., which can all severely degrade the system frequency stability. This can lead to under-/over-frequency load shedding, damage to turbine blades, and affect frequency-sensitive loads. In this study, we propose a methodology to improve the two critical frequency stability indices, i.e., the frequency nadir and the rate of change of frequency (RoCoF), by formulating an optimization problem. The size and placement location of battery energy storage systems (BESSs) are considered to be the constraints for the proposed optimization problem. Thereafter, the optimization problem is solved using the three metaheuristic optimization algorithms: the particle swarm optimization, firefly, and bat algorithm. The best performing algorithm is then selected to find the optimal sizing and placement location of the BESSs. The analyses are all performed on the IEEE 9-bus and IEEE 39-bus test systems. Several scenarios which consider multiple generator outages, increased/decreased loading conditions, and the addition of RESs are also considered for both test systems in this study. The obtained results show that under all scenarios, the proposed method can enhance system frequency compared to the existing method and without BESSs. The proposed method can be easily upscaled for a larger electrical network for obtaining the optimized BESS size and location for the improvement of the system frequency stability. [ABSTRACT FROM AUTHOR]

In the context of frequency stability in a two-area microgrid, it is crucial to address the fluctuations in frequency caused by load disturbances. To achieve this, an effective loadfrequency control (LFC) system, which serves as the secondary control, must be implemented. However, the presence of renewable energy sources such as wind turbines and photovoltaic systems adds complexity to the operation of the LFC system due to their inherent uncertainty. To enhance the performance of the LFC system in the two-area microgrid, this paper proposes a reduction in the number of controllers employed, aiming for a less complex structure. Specifically, Model Predictive Control (MPC) is utilized for LFC, and the weight parameters of the MPC controller are determined using Crazinessbased Particle Swarm Optimization (CRPSO). The proposed method is compared with alternative approaches, including PID controller optimized with Social Spider Optimization (SSO), Fractional Order Fuzzy PI (FOFPI), and conventional MPC. The effectiveness of the proposed method is evaluated in various scenarios, considering load variations and the presence of distributed microgrid generation resources. The results demonstrate that the proposed method outperforms the other controllers in terms of speed of response, reduction of overshoot and undershoot, and overall complexity. Importantly, the proposed method significantly improves the frequency stability of the two-area microgrid. The simulation and analysis are conducted using MATLAB software, providing a comprehensive understanding of the system dynamics and the performance of the proposed controller. [ABSTRACT FROM AUTHOR]

Abstract As inverter‐based resources like wind turbines increase, grid inertia and stability decrease. Optimal placement and control of energy storage systems can stablise low‐inertia grids. This paper investigates how optimal battery energy storage systems (BESS) enhance stability in low‐inertia grids after sudden generation loss. The sitting, sizing and control of BESS are determined simultaneously in each genetic algorithm (GA) population, then voltage and frequency stability is evaluated based on the network simulation. This continues until the optimal solution is found. A network based on Kundur's four‐machine system is modelled for the first study and two of the four synchronous generators (SGs) have been replaced with wind farms. Then, the production of the third SG has been decreased by 13%. According to the results, addition of wind farms causes the frequency drop below 49.6 Hz for more than 5 min, indicating instability. It is also demonstrated that with optimal control parameters and placement, a 60 MW BESS can alleviate the voltage and frequency fluctuations, leading to enhanced stability. This method has also been tested on the IEEE 39‐bus network, where the installation of a BESS with a capacity of 9 MVA could restore the frequency stability.