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The present work investigates the energy performance analysis of a heptad‐based multiple‐stage evaporator (MSE) under steady and transient conditions, integrated with different energy reduction schemes (such as steam split, feed split, and feed preheater). The steady‐state analysis was performed to optimize the steam economy subjected to the developed steady‐state energy models as the equality constraints. The simulated optimization is a maximization problem and is solved by Interior‐Point Optimizer and Gray Wolf Optimizer on two different platforms, GAMS and MATLAB, respectively. Further, transient and stability analyses were performed by developing and representing the nonlinear dynamic energy models to the state‐space representation using linearization. [ABSTRACT FROM AUTHOR]

Mass-impregnated (MI) cables have been used for many years as cables in high-voltage direct current (HVDC) systems. In line commutated converter (LCC) HVDC systems, polarity reversal for power flow control can induce significant electrical stress on MI cables. Furthermore, the mass oil and kraft paper comprising the impregnated insulation have significantly different coefficients of thermal expansion. Load fluctuations in the cable lead to expansion and contraction of the mass, creating pressure within the insulation and causing redistribution of the impregnant. During this process, shrinkage cavities can form within the butt gaps. Since the dielectric strength of the cavities is lower than that of the surrounding impregnation, cavitation phenomena in impregnated paper insulation are considered a factor in degrading insulation performance. Consequently, this study analyzes the electrical conductivity of thermally aged materials and investigates the transient electric field characteristics within the cable. Additionally, it closely analyzes the formation and dissolution of cavities in MI cables during polarity reversal based on a numerical model of pressure behavior in porous media. The conductivity of the impregnated paper indicates that it has excellent resistance to thermal degradation. Simulation results for various load conditions highlight that the interval of load-off time and the magnitude of internal pressure significantly influence the cavitation phenomenon. Lastly, the study proposes stable system operation methods to prevent cavitation in MI cables. [ABSTRACT FROM AUTHOR]

This work evaluates the effect of self‐alignment on the performance of bottom‐gate IGZO TFTs for AMOLED backplanes via SPICE simulation. Transient simulations are used to evaluate the row and column scaling of self‐aligned and non‐self‐aligned IGZO TFT to make quantitative comparisons in terms of line, settle and discharge time. Essentially, this work addresses the following questions: (1) given that self‐aligned TFTs have lower mobility than non‐self‐aligned TFTs due to large differences in contact resistance, does the lower overlap capacitance of self‐aligned TFTs always lead to better transient performance than non‐self‐aligned TFTs? and (2) Under what condition(s) do non‐self‐aligned TFTs become comparable to self‐aligned TFTs in terms of transient performance? [ABSTRACT FROM AUTHOR]

This paper introduces a new model for transient moisture equilibrium in oil-paper insulation, easily applicable even in a continuous way, based on Fick's second law. According to the model, the moisture concentration in paper follows step response function, but the equilibration time constant changes with time since it depends on temperature, paper thickness, equilibration moisture in oil-paper insulation, and number of oil-paper interfaces. The model is validated against experimental data. [ABSTRACT FROM AUTHOR]

• At steady-state excitation, the transient electric field distribution in typical multi layer oil-paper insulation at different aging stages was obtained. • The equivalent model of polarization conductivity was proposed, which characterized the nonlinear phenomena at different polarization voltages. • Based on the charge escape trap model, the mechanism of the nonlinear phenomenon of response current in the process of dielectric polarization was revealed. The oil-immersed transformer plays a pivotal role in the power network. Its insulation stability is essential. At present, the application of time-domain dielectric response technology in insulation detection of oil-immersed equipment is relatively mature. However, there is a contradiction between increasing the test excitation amplitude to improve the test accuracy and the nonlinear response characteristics of the test dielectric at high-voltage excitation. The assessment theories all depend on the laboratory test results, and inaccurate test results will affect the assessment results. Therefore, this paper prepared several groups of insulation-scaled aging models in the laboratory and studied the effects of temperature and test excitation amplitude on the polarization and depolarization characteristics of the models. During the polarization process, the electric intensity variation was calculated. Meanwhile, at the time-varying electric field, the influence mechanism of electric intensity on the response current caused by the charge escaping from the trap during the polarization process was obtained. This paper quantified the relationship between the aging state and the height of the interfacial polarization barrier. The study of nonlinear dielectric response in the time domain will help to improve the accuracy of test results when diagnosing the insulation performance of oil-immersed transformers. [ABSTRACT FROM AUTHOR]

The effect of HV impulses on surface and cavity partial discharges (PD) of oil-impregnated paper (OIP) is investigated in this work, by subjecting specimens to impulse voltages superimposed on a continuous AC voltage. The superposition of transient and AC voltage is relevant to insulation systems in power-system equipment, which is exposed to transients such as lightning and switching impulses during its operation. For several different PD-generating defects in oil-impregnated paper, the PD behaviors before and after the impulse are compared. The influence of moisture content is studied by using OIP with moisture content <0.5%, 3.0% and 5.5%. The results show a distinctive behavior of PD due to the impulse for each defect and insulation condition, either by change in the PD rate and magnitude or by causing PD inception or extinction. Recordings of the voltage signals and associated PD measurements during and after the incidence of a high voltage transient are of potential use for condition assessment of the insulation of power transformers and their bushings, as a form of online diagnostics. [ABSTRACT FROM AUTHOR]

The Buck converter is a commonly used voltage regulator (VR) structure that supplies power to the load devices and responds to load transients. In most of the applications, the VR is controlled by voltage or current mode control, and some nonlinear approaches are used to improve the transient response which brings more complexities to the closed loop design. To achieve a fast transient response without over-regulation under a load step transient, this paper proposes a digital single-cycle regulation (SCCR) controller, which comprised a fast path, a slow path, and a neutralization path. Unlike the conventional PID control, the neutralization path of the SCCR controller is used to offset the excessive energy change in the first cycle after a load step occurs, which makes the inductor current reach its new static condition in a shorter period of time. The mathematical model of the SCCR control is established in this paper and a scanning algorithm is proposed for the design of the compensator parameters. Experimental results are presented to verify the improvement of the transient response when compared to the conventional and nonlinear PID control, the recovery time is decreased by 64.3% and 43% for load step-up and step-down when compared with nonlinear PID control. [ABSTRACT FROM AUTHOR]

This paper attempts to elucidate the transformative integration of computational techniques within power systems, underscoring their critical role in enhancing system modeling, control, and the efficient integration of renewable energy. It breaks down the two-sided nature of technological progress, highlighting both gains in operational efficiency and new challenges such as real-time processing, data management, and cybersecurity. Through meticulous analysis of query-based research patterns and mathematical frameworks, this study delves into the balancing act between specificity and breadth in scholarly inquiries while evaluating the impact and evolution of research trends through citation analysis. The convergence of interests and transient research trends is evident, particularly in Artificial Intelligence and optimization. This comprehensive narrative anticipates a sophisticated trajectory for power systems, advocating for continuous innovation and strategic research to foster sustainable, resilient, and intelligent energy networks. [ABSTRACT FROM AUTHOR]

Lightning strikes can cause equipment damage and power outages, so the distribution system's reliability in withstanding lightning strikes is crucial. This research paper presents a model that aims to optimise the configuration of a lightning protection system (LPS) in the power distribution system and minimise the System Average Interruption Frequency Index (SAIFI), a measure of reliability, and the associated cost investment. The proposed lightning electromagnetic transient model considers LPS factors such as feeder shielding, grounding design, and soil types, which affect critical current, flashover rates, SAIFI, and cost. A metaheuristic algorithm, PSOGSA, is used to obtain the optimal solution. The paper's main contribution is exploring grounding schemes and soil resistivity's impact on SAIFI. Using 4 grounding rods arranged in a straight line under the soil with 10 Ωm resistivity reduces grounding resistance and decreases SAIFI from 3.783 int./yr (no LPS) to 0.146 int./yr. Unshielded LPS has no significant effect on critical current for soil resistivity. Four test cases with different cost investments are considered, and numerical simulations are conducted. Shielded LPSs are more sensitive to grounding topologies and soil resistivities, wherein higher investment, with 10 Ωm soil resistivity, SAIFI decreases the most by 73.34%. In contrast, SAIFIs for 1 kΩm and 10 kΩm soil resistivities show minor decreases compared to SAIFIs with no LPS. The study emphasises the importance of considering soil resistivity and investment cost when selecting the optimal LPS configuration for distribution systems, as well as the significance of LPS selection in reducing interruptions to customers. [ABSTRACT FROM AUTHOR]

The data-driven transient stability assessment (TSA) of power systems can predict online real-time prediction by learning the temporal features before and after faults. However, the accuracy of the assessment is limited by the quality of the data and has weak transferability. Based on this, this paper proposes a method for TSA of power systems based on an improved extreme gradient boosting (XGBoost) model. Firstly, the gradient detection method is employed to remove noise interference while maintaining the original time series trend. On this basis, a focal loss function is introduced to guide the training of the XGBoost model, enhancing the deep exploration of minority class samples to improve the accuracy of the model evaluation. Furthermore, to improve the generalization ability of the evaluation model, a transfer learning method based on model parameters and sample augmentation is proposed. The simulation analysis on the IEEE 39-bus system demonstrates that the proposed method, compared to the traditional machine learning-based transient stability assessment approach, achieves an average improvement of 2.16% in evaluation accuracy. Specifically, under scenarios involving changes in topology structure and operating conditions, the accuracy is enhanced by 3.65% and 3.11%, respectively. Moreover, the model updating efficiency is enhanced by 14-15 times, indicating the model's transferable and adaptive capabilities across multiple scenarios. [ABSTRACT FROM AUTHOR]

Presents a study that examined the aging process of mineral oil-impregnated-high density kraft paper capacitor bushing models subjected to voltage switching surges. Effects of the removal of electrical impulse stress over a finite time period; Thickness of the insulating system of the model capacitor bushing; Implication of the partial discharged inception stress characteristics for the doubled insulation specimen.

In traditional diamond cutting, the cutting force is usually large and it will affect tool life and machining quality. Elliptical vibration cutting (EVC) as one of the ultra-precision machining technologies has a lot of advantages, such as reduces cutting force, extend tool life and so on. It’s difficult to predict the transient cutting force of EVC due to its unique elliptical motion trajectory. Study on chip formation will helpfully to predict cutting force. The geometric feature of chip has important effects on cutting force, however, few scholars have studied the chip formation. In order to investigate the time-varying cutting force of EVC, the geometric feature model of chip is established based on analysis of chip formation, and the effects of cutting parameters on the geometric feature of chip are analyzed. To predict transient force quickly and effectively, the geometric feature of chip is introduced into the cutting force model. The calculated results show that the error between the predicted cutting force in this paper and that in the literature is less than 2%, which proves its feasibility. [ABSTRACT FROM AUTHOR]

When the electromagnetic transient simulation of a large-scale power grid is carried out, because the simulation is limited by the scale of simulation software, it is necessary to divide the grid into internal and external grids, and the external grid is modeled with equivalent simplification. Aiming at resolving the difficulties of the traditional grid equivalence method, such as a cumbersome calculation process and harsh calculation conditions, a static grid equivalence method based on the genetic algorithm is proposed in this paper. The method first constructs an external grid equivalence network, which includes coupling branches between boundary nodes, and each boundary node is connected to the external grid equivalence power supply through the branches. Then, the external grid equivalence model is used to establish an optimization model for solving the equivalence network parameters based on the information of the internal network, the difference of the power input from the external grid to the boundary nodes before and after equivalence is used as the objective function, and the genetic algorithm is used to realize the iterative optimization of the objective function to obtain a set of optimal post-equivalence network model parameters so that the state variables of the internal power grid before and after the equivalence are matched. The accuracy and effectiveness of the proposed method are verified through simulation with the CERPI36V7 node system. [ABSTRACT FROM AUTHOR]

The synchronous virtualmachine uses inverter power to imitate the performance of the conventional synchronous machine. It also has the same inertia, damping, frequency, voltage regulation, and other external performance as the generator. It is the key technology to realize new energy grid connections' stable and reliable operation. This project studies a dynamic simulation model of an extensive new energy power system based on the virtual synchronous motor. A new energy storage method is proposed. The mathematical energy storage model is established by combining the fixed rotor model of a synchronous virtual machinewith the charge-discharge power, state of charge, operation efficiency, dead zone, and inverter constraint. The rapid conversion of energy storage devices absorbs the excess instantaneous kinetic energy caused by interference. The branch transient of the critical cut set in the system can be confined to a limited area. Thus, the virtual synchronizer's kinetic and potential energy can be efficiently converted into an instantaneous state. The simulation of power system analysis software package (PSASP) verifies the correctness of the theory and algorithm in this paper. This paper provides a theoretical basis for improving the transient stability of new energy-connected power grids. [ABSTRACT FROM AUTHOR]

Independent lightning rods are often installed in substation grounding systems for lightning protection. The concentrated discharge channel formed when a lightning current flows to the ground through a grounding electrode will cause electromagnetic interference to the directly buried secondary cable. And the three-dimensional structure of the discharge channel will affect the transient electromagnetic field distribution, thereby affecting the electromagnetic transients on cable shields. In order to explore the influence of soil discharge phenomena on the electromagnetic interference of the directly buried secondary cable, in this paper, we carried out experiments on cables in two different grounding modes, single-ended and double-ended grounding, and captured image of soil discharge channels. The results show that the cable grounding mode will affect the coupling mode that causes the shielding layer current. The relative spatial position of the soil discharge channel and the cable has a significant impact on the magnitude of the shielding layer current under both grounding modes. The water content and salt content of the soil also have different degrees of influence on the coupling current of the shielding layer in different grounding modes. [ABSTRACT FROM AUTHOR]

The transient stability assessment based on machine learning faces challenges such as sample data imbalance and poor generalization. To address these problems, this paper proposes an intelligent enhancement method for real-time adaptive assessment of transient stability. In the offline phase, a convolutional neural network (CNN) is used as the base classifier. A model training method based on contrastive learning is introduced, aiming to increase the spatial distance between positive and negative samples in the mapping space. This approach effectively improves the accuracy of the model in recognizing unbalanced samples. In the online phase, when real data with different distribution characteristics from the offline data are encountered, an active transfer strategy is employed to update the model. New system samples are obtained through instance transfer from the original system, and an active sampling strategy considering uncertainty is designed to continuously select high-value samples from the new system for labeling. The model parameters are then updated by fine-tuning. This approach drastically reduces the cost of updating while improving the model's adaptability. Experiments on the IEEE39-node system verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

High altitude electromagnetic pulse (HEMP) couples to cables and introduces interference into the connected electronic equipment. Responses arising from the transient electromagnetic field typically follow an exponentially damped sinusoid behavior. Thus, damped sinusoids with different parameters are recommended in the International Electrotechnical Commission (IEC) standards as typical injected waveforms for HEMP conducted immunity test. To guarantee the compliance of the injected pulse, accurate measurement of the injected pulse is needed. Wideband proportional current sensors are often applied to measure the injected damped sinusoid. However, bandwidth requirements of wideband proportional current sensor for damped sinusoid measurement are not specified. In this paper, two formulae are deduced to establish the relationships between the bandwidth requirements and the fundamental resonance frequency of the damped sinusoid to be measured. It is convenient and simple for the on-site engineers to check whether the bandwidth of the proportional current sensor is suitable by the formulae. Monte-Carlo simulation is conducted in support of the recommended formulae. [ABSTRACT FROM AUTHOR]

The large integration of inverter-based resources will significantly alter grid dynamics, leading to pronounced stability challenges due to fundamental disparities between inverter-based and traditional energy systems. While grid-following inverters (GFLIs) dominate current inverter configurations, their increased penetration into the grid can result in major stability issues. In contrast, grid-forming inverters (GFMIs) excel over GFLIs by offering features like standalone operation, frequency support, and adaptability in weak grid scenarios. GFMIs, unlike GFLIs, control the AC voltage and frequency at the common coupling point, impacting the inverter dynamic response to grid disturbances and overall stability. Despite the existing literature highlighting differences between GFLIs and GFMIs and their control strategies, a comprehensive review of GFMIs' stability and the effects of their control schemes on grid stability is lacking. This paper provides an in-depth evaluation of GFMIs' stability, considering various control schemes and their dynamics. It also explores different types of power system stability, introduces new stability concepts that correspond to power grids with integrated inverters, i.e., resonance and converter-driven stability, and reviews small-signal and transient stability analyses, which are the main two types of GFMI stability studied in the literature. The paper further assesses existing studies on GFMI stability, pinpointing research gaps for future investigations. [ABSTRACT FROM AUTHOR]

This paper aims at estimating the life of extruded HVDC cable insulation subjected to fast and slow voltage polarity reversals (VPRs). An ad hoc MATLAB code is used for the transient electric field simulation in the cable insulation thickness by solving numerically Gauss, ohm, and current continuity equations beside a macroscopic conductivity equation. A transient temperature is also considered during slow VPR transients. The results show a significant localized reduction in the life of the inner insulation, making the life distribution non-monotonous inside the insulation thickness. The results show that fast VPRs are the most stressing transients in this study. The longer the duration of the zero-voltage period in slow VPR, the less stressed the insulation, hence, the longer the local life in the inner insulation of the cable. The latter is justified by the charge relaxation during slow VPRs. [ABSTRACT FROM AUTHOR]

In this paper, a new model predictive control termed as intelligent model predictive control (IMPC) combined with an improved new competitive swarm optimizer (CSO) is designed. The analytical predictive model is not necessarily established a priori in the proposed IMPC algorithm, and the control plant can be used directly as the predictive model to reduce the complexity of the algorithm. In addition, two new techniques, dynamic initialization and back steps methods, are proposed and utilized to improve the traditional CSO to realize constraints management during the optimization process. An application to aeroengine transient-state control is studied to verify the effectiveness of the presented IMPC algorithm. It is shown that, benefitting from the IMPC algorithm, the control task is well completed and all the constraints are satisfied. Practical Applications: This paper proposes a new optimization algorithm to solve some complex optimization problems with constraints. The designed new optimization algorithm is simple and easy to implement and it is more suitable for applications with black-box models or complex optimization objective functions compared with some existing optimization algorithms. This paper may provide some help to researchers who are interested in model predictive control or metaheuristic algorithms and to people whose work contains some complex optimization problems. This paper also provides a design method of aeroengine transient-state control plans. The simulation results showed that compared with some existing control methods or optimization algorithms, the aeroengine could accelerate to the desired steady-state point with shorter transient time and all constraints are satisfied when utilizing the proposed new optimization algorithm. [ABSTRACT FROM AUTHOR]

Electric power generation is quickly transitioning toward nontraditional inverter-based resources (IBRs). Prevalent devices today are solar PV, wind generators, and battery energy storage systems (BESS) based on electrochemical packs. These IBRs are interconnected throughout the power system via power electronics inverter bridges, which have sophisticated controls. This paper studies the impacts and benefits resulting from the integration of grid forming (GFM) inverters and energy storage on the stability of power systems via replicating real events of loss of generation units that resulted in large load shedding events. First, the authors tuned the power system dynamic model in Power System Simulator for Engineering (PSSE) to replicate the event records and, upon integrating the IBRs, analyzed the system dynamic responses of the BESS. This was conducted for both GFM and grid following (GFL) modes. Additionally, models for Grid Forming Static Synchronous Compensator (GFM STATCOM), were also created and simulated to allow for quantifying the benefits of this technology and a techno-economic analysis compared with GFM BESSs. The results presented in this paper demonstrate the need for industry standardization in the application of GFM inverters to unleash their benefits to the bulk electric grid. The results also demonstrate that the GFM STATCOM is a very capable system that can augment the bulk system inertia, effectively reducing the occurrence of load shedding events. [ABSTRACT FROM AUTHOR]

This article explores the impact of electric vehicle (EV) charging on power systems and emphasizes the importance of careful analysis and planning. It discusses various topics related to EV charging, including EV hosting capacity, optimal placement of EVs and charging stations, technical impacts of Vehicle-to-Grid (V2G) technology, shared vehicle rental, decentralised collaboration frameworks, intelligent energy management schemes, EV demand response, and optimal sizing and siting of public EV charging stations. The article provides valuable insights and solutions for utilities, academia, and policymakers to address the challenges and opportunities associated with EV charging. Additionally, the article introduces a new approach for determining the limits of transformers and overhead lines in relation to EV charging, using Monte Carlo simulations and proposing new parameters for evaluating maximum demands. The authors stress the need for further analysis and attention to the impact of EVs on power systems. [Extracted from the article]

Geophysical inversion usually involves ill-posed problem. Regularization is the most commonly used method to mitigate this problem. There are many regularization parameter selection methods, among which the adaptive regularization method can automatically update parameters during iteration, reducing the difficulty of parameter selection. Therefore, it is widely used in linear inversion. However, there are very few studies on the use of adaptive regularization methods in stochastic optimization algorithms. The biggest difficulty is that in stochastic optimization algorithms, the search direction of any iteration is completely random. Data fitting term and stabilizing term vary in a wide range, making it difficult for traditional methods to work. In this paper, we consider the contributions of the data fitting term and the stabilizing term in the objective function and give an improved adaptive regularization method for very fast simulated annealing (VFSA) inversion for transient electromagnetic (TEM) data. The optimized method adjusts the two terms dynamically to make them in balance. We have designed several numerical experiments, and the experimental results demonstrate that the method in this paper not only accelerates the convergence, but also the inversion results are very little affected by the initial regularization parameter. Finally, we apply this method to field data, and the inversion results show very good agreements with nearby borehole data. [ABSTRACT FROM AUTHOR]

The information technology and communication (IT&C) market consists of computing and telecommunication technology systems, which also include a variety of audio devices. Preserving the confidentiality of transmitted information through these devices stands as a critical concern across various domains and businesses. Notably, spurious electromagnetic emanations emitted by audio devices can be captured and processed, potentially leading to eavesdropping incidents. The evaluation of electronic devices for potential security vulnerabilities often involves employing Transient Electromagnetic Pulse Emanation Standard (TEMPEST) technology. This paper introduces a novel approach to TEMPEST testing specifically tailored for audio devices. The outcomes of the proposed approach offer valuable insights into TEMPEST equipment testing, aiming to mitigate the potential risks posed by threats exploitable by eavesdroppers in everyday scenarios. The present work delves into the examination of two ubiquitous global electronic devices: a notebook and a pair of in-ear headphones. The symmetrical framework of this study arises from the intrinsic similarity that, despite belonging to distinct categories, both devices possess the capability to emit electromagnetic emissions that contain compromised audio signals. This assertion is substantiated by the measurement results presented herein. The proposed methodology involves the analysis of the audio amplitude modulation (AM) demodulated signal in the frequency domain. This innovative approach not only mitigates operator fatigue but also significantly reduces the testing time required for these devices and instrument running hours and leads to the development of new applications. [ABSTRACT FROM AUTHOR]

Modern power systems are large in size and complex in features; the data collected by Phasor Measurement Units (PMUs) are often noisy and contaminated; and the machine learning models that have been applied to the transient stability assessment (TSA) of power systems are not sufficiently capable of capturing long-distance dependencies. All these issues make it difficult for data mining-based power system TSA methods to have sufficient accuracy, timeliness, and robustness. To solve this problem, this paper proposes a power system TSA model based on the transformer and neighborhood rough set. The model first uses the neighborhood rough set to deal with the redundant features of the power system trend data and then uses the transformer model to train the TSA model, in which various normalization methods such as Batch Normalization and Layer Normalization are introduced in the process to obtain better evaluation performance and speed up the convergence rate of the model. Finally, the model is evaluated by two evaluation indicators, F 1 − measure and accuracy, with values of 99.61% for accuracy and 0.9972 for F 1 − measure , as soon as the tests on noise contamination and missing data test results on the IEEE39 system show that the NRS-Transformer model proposed in this paper is superior in terms of prediction accuracy, training speed, and robustness. [ABSTRACT FROM AUTHOR]

The current existing problem of deep learning framework for the detection and segmentation of electrical equipment is dominantly related to low precision. Because of the reliable, safe and easy-to-operate technology provided by deep learning-based video surveillance for unmanned inspection of electrical equipment, this paper uses the bottleneck attention module (BAM) attention mechanism to improve the Solov2 model and proposes a new electrical equipment segmentation mode. Firstly, the BAM attention mechanism is integrated into the feature extraction network to adaptively learn the correlation between feature channels, thereby improving the expression ability of the feature map; secondly, the weighted sum of CrossEntropy Loss and Dice loss is designed as the mask loss to improve the segmentation accuracy and robustness of the model; finally, the non-maximal suppression (NMS) algorithm to better handle the overlap problem in instance segmentation. Experimental results show that the proposed method achieves an average segmentation accuracy of mAP of 80.4% on three types of electrical equipment datasets, including transformers, insulators and voltage transformers, which improve the detection accuracy by more than 5.7% compared with the original Solov2 model. The segmentation model proposed can provide a focusing technical means for the intelligent management of power systems. [ABSTRACT FROM AUTHOR]

The simulation of electric field transients in HVDC cables can be a fundamental tool to support insulation system design when operation dynamics, which includes voltage polarity inversions and load variation, becomes significant during the expected cable life. The field behavior during voltage and temperature transients is associated with intrinsic and extrinsic ageing processes that can affect the cable design life. Traditional models employed for electric field simulations consider only the non–linear, steady–state dependence of conductivity on temperature and field magnitude, but they neglect the transient behavior of permittivity and conductivity, that is, polarization and charge trapping phenomena. These processes impact on the duration of the field transient and thus ageing. This paper discusses the numerical implementation of an electro–quasistatic model that can be used to perform transient simulations of electric fields in HVDC cables insulation. With respect to the model traditionally employed, the presented one is extended with Debye's equations for dielectric polarization processes. The model is implemented numerically using finite differences, or the Occhini equivalent circuit: this paper demonstrates that the two approaches are equivalent. Numerical simulations show that, during transients, polarization processes slow down the electric field dynamics and reduce its maximum intensity. [ABSTRACT FROM AUTHOR]

The inherent constraints of grid‐forming converters affect their ability to maintain voltage source characteristics within a specific operational range. In response to these limitations, ongoing pilot projects involving grid‐forming technology have adjusted their current thresholds up to three times the rated current, significantly exceeding the traditionally threshold of 1.2 times the rated current. This paper aims to investigate the effects of current thresholds on the dynamic responses of grid‐forming converters under large disturbances, with the intention of identifying an optimal current threshold that meets the grid's demands for maintaining voltage source characteristics and overall stability. A novel power angle relationship is introduced, integrating current limits and anti‐windup voltage controls into the equivalent circuit models of these converters. Analytical expressions for stable and unstable equilibrium points are derived, improving insights into the converters' dynamic behaviour and their resilience to phase jumps across various current thresholds and short‐circuit ratios. Findings indicate that higher current thresholds substantially improve phase jump limits and withstand capabilities. The paper concludes with proposed configurations and optimization strategies for current thresholds, all supported by experimental validation. [ABSTRACT FROM AUTHOR]

This paper deals with the quasi-instantaneous determination (in a single-step response time) of apparent, active, and reactive (i.e., blind and distortion) power mean values including the total power factor, total harmonic distortion, and phase shift of fundamentals of a power electronic and electrical system (PEES) using the ip-iq method, which is the main contribution of the paper. The power components' mean values are investigated during the transient and steady states. The power components' mean values can be determined directly from phase current and voltage quantities, using an integral calculus over one period within the next calculation step and using moving average and moving rms techniques (or digital filtering). Consequently, the power factor can be evaluated with known values of a phase shift of fundamentals (using a Fourier analysis). The results of this study show how a distortion power component during transients is generated even under a harmonic supply and linear resistive–inductive load. The paper contains a theoretical base, modeling, and simulation for the three and single phases of the transients in power electronic systems. The worked-out results can be used to determine and size any PES. The presented approach brings a detailed time waveform verified by simulations in Matlab/Simulink 2022a and the Real-time HW Simulator Plecs RT Box 1. [ABSTRACT FROM AUTHOR]

Low carbon operation of power systems is a key way to achieve the goal of energy power carbon peaking and carbon neutrality. In order to promote the low carbon transition of energy and power and the coordinated and optimized operation of distributed energy sources in virtual power plants (VPP), this paper proposes a framework for collaborative utilization of pumped storage–carbon capture–power-to-gas (P2G) technologies. It also constructs a multi-time scale low carbon economic dispatch model for VPP to minimize the internal resource operation cost of VPP in each time period. During the intraday scheduling stage, the day-ahead scheduling results as the planned output and the energy flow is then dynamically corrected at a short-term resolution in the framework. This allows for the exploration of the low-carbon potential of each aggregation unit within the virtual power plant. The results of the simulation indicate that the strategy and model proposed in this paper can effectively encourage the consumption of renewable energy sources, promote the low-carbon operation of power system power, and serve as a valuable reference for the low-carbon economic operation of the power system. [ABSTRACT FROM AUTHOR]

The surge in electric vehicle adoption has resulted in a significant rise in end-of-life batteries, which are unsuitable for demanding EV applications. Repurposing these batteries for secondary applications presents a promising avenue to tackle environmental and economic challenges associated with their disposal. The second-life battery (SLB) approach emerges as a mechanism to manage this massive amount of retired EV batteries. However, this approach poses significant challenges in determining and monitoring battery degradation and performance. After evaluating different scenarios for reusing or recycling retired EV batteries, this paper examines the main challenges associated with SLBs, including techno-economic aspects, uncertainty from first life, safety, characterization and screening, battery-management systems, and secondary applications. A comprehensive review of current state-of-the-art SLB research and implementations is provided, particularly emphasizing battery characterization and the requisite evaluation processes for SLB eligibility. This paper explores diverse measurement techniques for assessing SLB performance, evaluating them based on accuracy, complexity, and time consumption, which are essential for achieving cost-effective SLB applications. The overarching objective is to thoroughly understand the principal challenges associated with repurposing EV batteries and delineate the research imperatives necessary for their successful implementation and prolonged lifespan. [ABSTRACT FROM AUTHOR]

This work aims to review the state of the art of the most important circuit synthesis techniques of rational approximation of electromagnetic multiport systems in order to incorporate them into a circuit simulator. In particular, equivalent circuits for the state‐space or for the pole/residue representation of impedances, admittances, and scattering parameters are reviewed in details. Furthermore, a novel contribution is given to show how it is possible to migrate from a state‐space (S,Y,Z) representation to another one by applying different matrix transformations. The resulting equivalent circuits can then be connected to linear/nonlinear devices or lumped elements in a Spice‐like framework allowing to analyze mixed electromagnetic/circuit problems. The validity of all the presented equivalent circuits and state‐space transformation is tested through two pertinent numerical examples. Pseudocodes are provided in order to make the reader able to easily implement the revised synthesis techniques. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we describe electrophoresis of charged particles in a thin layer of a nonpolar liquid between two insulating substrates because this configuration is common in recently developed in-plane electronic paper. In the in-plane electrophoresis experiments a model system of charged inverse micelles in dodecane has been used which is well understood from studies of out-of-plane electrophoresis. The transient current due to drift and diffusion of charged inverse micelles is measured in thin in-plane devices upon application of a voltage step. For the modelling of the transient dynamics of charged inverse micelles without chemical reactions or convection a 1-dimensional approximation of the Poisson–Nernst–Planck (PNP) equations is developed. This approximation is valid for a sufficiently thin in-plane device and allows much faster calculations. Firstly, it is verified in the case of a sufficiently thin in-plane device and high applied voltage that the 1-dimensional approximation is in good agreement with the solution of the full 2-dimensional PNP equations with finite elements implementation. Then, the 1-dimensional approximation is used to study the transient current and trajectories of trace amounts of charged colloidal particles in different regimes depending on the screening of the electric field. Also a comparison is made to the well-studied case of out-of-plane electrophoresis. Finally, it is verified that for voltages much larger than the thermal voltage the experimental results are in good agreement with the 1-dimensional approximation, indicating that the charge transport dynamics of charged inverse micelles in the bulk are described well by the model. [Copyright &y& Elsevier]

The nearest level modulation (NLM) is used to automatically generate ac side voltages of sub‐modules in modular multilevel converter (MMC). Existing literature seldom presents models that describe complex NLM processes. This paper proposes an equivalent model of the NLM to simply describe and simulate the complex NLM process. The main contribution of this study is to build the model of NLM with fast simulation speed for the application focuses on the simulation accuracy at the millisecond level. The duty cycle of the average model generated by the NLM in sub‐modules of the MMC is divided into two components, which are the stable component for generating the bridge arm voltage and the fluctuation component for balancing the dc side voltage of sub‐modules, respectively. The stable component is generated by the modulation wave of the MMC control system. By adding a voltage control closed loop to the sub‐module, the fluctuation component for balancing the dc side voltages of sub‐modules can automatically adjust the ac side voltages of sub‐modules. The proposed equivalent model of NLM improves the simulation speed and has the same effect with the traditional NLM within the low‐frequency range or with the time step of millisecond level. [ABSTRACT FROM AUTHOR]

Multi‐terminal high‐voltage direct current technology based on voltage‐source converter stations (VSC‐MTDC) is expected to be one of the most important contributors to the future of electric power systems. In fact, among other features, it has already been shown how this technology can contribute to improve transient stability in power systems by the use of supplementary controllers. Along this line, this paper will investigate in detail how these supplementary controllers affect electromechanical oscillations, by means of small‐signal stability analysis. The paper analyses two control strategies based on the modulation of active‐power injections (P‐WAF) and reactive‐power injections (Q‐WAF) in the VSC stations which were presented in previous work. Both control strategies use global signals of the frequencies of the VSC‐MTDC system and they presented significant improvements on transient stability. The paper will provide guidelines for the design of these type of controllers to improve both large‐ and small‐disturbance angle stability. Small‐signal stability analysis (in Matlab) has been compared with non‐linear time domain simulation (in PSS/E) to confirm the results using CIGRE Nordic32A benchmark test system with a VSC‐MTDC system. The paper analyses the impact of the controller gains and communication latency on electromechanical‐oscillation damping. The main conclusion of the paper is that transient‐stability‐tailored supplementary controllers in VSC‐MTDC systems can be tuned to damp inter‐area oscillations too, maintaining their effectiveness. [ABSTRACT FROM AUTHOR]

The concept of the digital twin has been adopted as an important aspect in digital transformation of power systems. Although the notion of the digital twin is not new, its adoption into the energy sector has been recent and has targeted increased operational efficiency. This paper is focused on addressing an important gap in the research literature reviewing the state of the art in utilization of digital twin technology in microgrids, an important component of power systems. A microgrid is a local power network that acts as a dependable island within bigger regional and national electricity networks, providing power without interruption even when the main grid is down. Microgrids are essential components of smart cities that are both resilient and sustainable, providing smart cities the opportunity to develop sustainable energy delivery systems. Due to the complexity of design, development and maintenance of a microgrid, an efficient simulation model with ability to handle the complexity and spatio-temporal nature is important. The digital twin technologies have the potential to address the above-mentioned requirements, providing an exact virtual model of the physical entity of the power system. The paper reviews the application of digital twins in a microgrid at electrical points where the microgrid connects or disconnects from the main distribution grid, that is, points of common coupling. Furthermore, potential applications of the digital twin in microgrids for better control, security and resilient operation and challenges faced are also discussed. [ABSTRACT FROM AUTHOR]

Recently, the power systems with a high penetration of renewables and power electronics have come into being. In these power systems, complex system dynamics, emergency faults, and insufficient frequency regulation reserve pose threats to system frequency stability. Based on the clustering development of energy storage, to ensure the system frequency stability when emergency faults occur, this paper proposes a decentralized frequency emergency control (FEC) strategy considering the participation of energy storage clusters (ESCs). First, the overall framework of the optimal-droop-based FEC strategy is introduced, which achieves the coordination between FEC and conventional frequency regulation strategies. Second, to appropriately allocate the unbalanced power among the generators and ESCs, a general design method for optimal droop coefficients is proposed, which is applicable to various control objectives. The optimality of the droop coefficients is rigorously proven. This case study is carried out on an electromagnetic transient simulation platform, and the simulation results verify the effectiveness and optimality of the proposed FEC strategy. [ABSTRACT FROM AUTHOR]

The Hybrid Power Flow Controller (HPFC) has a simple design configuration, where the upgrading of the line functionality and controller can be performed in stages. This paper applies two HPFC configurations to a multi-machine power network. The first HPFC is a combination of two static synchronous series compensators (SSSC) connected in series, and a Static Var compensator (SVC). The second one consists of two shunt Static synchronous compensators (STATCOM) connected through a Thyristor controlled series compensator (TCSC), across a coupling transformer in a common DC link. The HPFC topologies are tested with a multi-machine power network with faults, in the presence of solar and wind energy sources. The overall model is simulated using SimPowerSystems toolbox and the performance of the two HPFC topologies is compared under various operating conditions. The comparison of simulation results shows that the second HPFC gives a better view than the first in analyzing the power system transient stability. [ABSTRACT FROM AUTHOR]

The work is based on a collaboration between Hiroshima University and Kure KOSEN College. This paper presents the design concept, hardware, and applications of a single-phase synchronous inverter (SSI), a specially designed grid-forming inverter (GFM) for single-phase micro-grid (SMGs). The SSI is designed for the conventional 100/200 V distribution network and is based on the concept of "Non-Interference Core (NIC) dynamic model". Novel contributions of this paper are: (1) A root mean square (RMS) model of NIC-SSI was developed, combined with the conventional power system model, and verified through the comparison with the hardware-in-the-loop (HIL) simulation and SSI hardware experiments; (2) using the developed RMS simulation tool, the stabilization effect of the SSIs was investigated in condition under which the SSIs are massively installed in a distribution system; (3) off-grid SMG operations using SSIs under various ill-conditioned loads were demonstrated. The results show that the SSI has the considerable ability of grid stability enhancements for frequency, transient, and small-signal stabilities. The proposed SMG using SSIs is promising. [ABSTRACT FROM AUTHOR]

Constructing a new energy-based power system is not only an important direction for the transformation and upgrade of China's power system, but also a key to achieving peak carbon and carbon neutrality. How to fully utilize situation awareness technology to adapt to diverse and differentiated scenarios has become a crucial breakthrough point for ensuring the reliable, safe, high-quality, low-carbon, and economical operation of the new power system. Starting from the distribution network demand resources, this paper proposes a dynamic aggregation method for load aggregators considering the user deviation quantity, to deal with the current situation that the adjustable load-side resource points are multi-faceted and wide, and the operating subjects are complex and difficult to participate directly in the grid dispatch. First, considering there is subjectivity in the electricity behavior of users under the jurisdiction of the load aggregator, a deviation amount may be generated during the actual aggregation process, which reduces the profit of the load aggregator. Therefore, a load aggregator-level user deviation dynamic volume forecasting method based on the Markov chain is proposed, which is used to predict the deviation quantity of users during the dispatch cycle and achieve a dynamic status estimate on the load side of the new power system. On this basis, a dynamic aggregation model for load aggregators based on the deviation volume was constructed with the objective of maximizing the revenue of load aggregators. The examples, by comparing the aggregation results of users under three scenarios, show the proposed method can effectively guarantee the income of load aggregators, verify the effectiveness of the proposed dynamic aggregation strategy, and provide technical support for the operation situation awareness of the load side of the new power system. [ABSTRACT FROM AUTHOR]

With the penetration of the high proportion of power electronics interfaced energy resources, the frequency stability issue in power systems is becoming increasingly prominent. This paper proposes a coordinated control strategy of multiple voltage source converter based high voltage direct current transmission (VSC‐HVDC) to simultaneously improve the transient frequency and steady‐state frequency after a severe disturbance. Firstly, a modified average system frequency response (MASFR) model is constructed with reserve power limitation, which takes into account the frequency responses of different types of generators (thermal, hydro and new energy resources). Secondly, according to the frequency stability requirements, the corresponding constraints, which consider the overload capacity of VSC‐HVDC, the AC transmission capacity and the frequency of AC grids on both sides of VSC‐HVDC, are formulated. Thirdly, for the transient frequency control, the coordinated optimization control model of multiple VSC‐HVDC is established, which aims to minimize the control energy considering the transient frequency threshold. For the steady‐state frequency control, the coordinated optimization control model is fomulated, which aims to minimize the control cost while considering the steady‐state frequency threshold. The two control schemes achieve seamless and smooth switching. Finally, the correctness and effectiveness of the proposed control strategy are verified in the improved IEEE 39 bus system. [ABSTRACT FROM AUTHOR]

This paper presents the dynamic voltage stability index based on the voltage oscillation loop for power systems integrated with multiple permanent magnet synchronous generators (PMSGs) to assess the dynamic interaction on voltage stability. First, the model of power systems integrated with multi-PMSGs using a Q--V sensitivity matrix as feedback to connect all PMSGs is established. The transfer function model between voltage and reactive power is derived, and the voltage oscillation loop can be derived, which exists in each PMSG. Next, the dynamic voltage stability index is theoretically derived and given, the impact of dynamic interaction among multi-PMSGs on voltage stability can be quantified, and the source of voltage oscillation can be identified and determined. Then, the voltage stability is recovered by shedding the trouble-making PMSG. The parameters of PMSGs could be tuned with the guidance of the dynamic voltage stability index to reduce the risk of voltage oscillation. Finally, the example of a test system with PMSGs is used to validate the correctness of the dynamic stability index. [ABSTRACT FROM AUTHOR]

Summary: In this paper, a multiphase digital control called digital integration constant on‐time (DICOT) control is proposed, which applies the concept of signal accumulation, solves the drawbacks of ripple‐based digital COT control that the switching frequency and transient performance are affected by the A/D sample delay and sampling noise. Besides, the multiphase interleaving approach of the proposed DICOT control is well‐suitable for digital control and no higher calculation frequency is required compared to single‐phase. In the aspect of the current balance, almost all existing researches work on analog COT current balance scheme and few works are investigating the resolution improvement of digital COT current balance. In this paper, the current balance model of multiphase COT control is derived and can be applied in the Buck system with an arbitrary number of phases, the delay‐line‐based high‐resolution COT current balance scheme is proposed to enhance the control resolution. Finally, the two‐phase DICOT control is tested on the multiphase Buck system, the transient performance is tested of 100 A load step with the slew rate of 1000 A/μs, and the voltage undershoot and overshoot are 20 and 36 mV, respectively. The current balance is tested and the errors are 0.01% and 0.11% at the light and heavy loads, respectively. [ABSTRACT FROM AUTHOR]

The advent of distributed generation has brought with it a plethora of challenges for the nascent power systems that are being deployed on a large scale. Firstly, the majority of power electronic converters connected to the grid are in current source mode, which results in a lack of inertia and an inability to provide effective inertia or achieve damping support during fluctuations in grid frequency. Secondly, the issue of power quality, caused by the presence of harmonics, is becoming increasingly severe. This is particularly problematic in microgrids or systems with high line impedance, where harmonics can be amplified, thereby further compromising the stability of the power system. To address the deficiency in system inertia, numerous scholars are currently utilizing grid-forming (GFM) technology to achieve virtual inertia. In order to address the issue of system harmonics, it is possible to install active power filter (APF) devices at the point of common coupling (PCC), which serve to mitigate the effects of harmonics. This paper puts forth a proposal for the implementation of an APF with virtual inertia, based on PR + RC composite control. This composite control mechanism serves to enhance the harmonic suppression capabilities of the APF. The introduction of a frequency droop enables the capacitor voltage amplitude to be adjusted during fluctuations in system frequency, thereby achieving virtual inertia and providing active support for system frequency. The experimental results demonstrate that this strategy not only reduces the total harmonic distortion (THD) by 13% in comparison to PI control, indicating excellent harmonic suppression performance, but also allows the system to be inert, achieving positive results in suppressing frequency fluctuations during transients. [ABSTRACT FROM AUTHOR]

Introduction. Insulation coordination requires accurate prediction of overvoltages at various points within a substation. Computer simulations of electromagnetic transients in real structures of substations become more precise due to the improvements of used models. Goal. This paper discusses in a first step the use of the modified ZnO arrester dynamic model alongside other substation equipment models, considering electrical phenomena like the corona model for reproducing the stresses that lightning can cause in an air-insulated substation and (method) then conducting a statistical approach based on the Monte Carlo method. The implemented MATLAB/ATP procedure estimates not only the substation Mean Time between Failures (MTBF), but also is used to select surge arresters or substation basic insulation levels (BILs). In this procedure ATP transients program is used to calculate lightning overvoltages and multicore environment for the calculations. Results. The obtained MTBF curves offer guidance for selecting appropriate insulation levels based on specific system requirements and conditions. The obtained results comply well with existing international insulation standards. This valuable approach significantly contributes to the field of lightning protection. References 31, tables 3, figures 10. [ABSTRACT FROM AUTHOR]

With the deep coupling between the cyber side and the physical side of power systems, the failure of any link of both sides may lead to power outages, so it is necessary to analyze their vulnerability and vulnerable links for targeted improvement of systems. By dynamically attacking the coupled network nodes, this paper proposes a multilevel model and node-to-edge cyber-physical power system and the corresponding indexes system to analyze the vulnerability of the coupled power grid and its key components. The results showed that in the order of the indexes proposed in this paper, attacking surviving power nodes and cyber nodes results in a network crash rate of 25.0% and 66.7% faster than that in the order of "betweenness" and that attacking surviving cyber nodes results in a network crash rate of 89.4% faster than that in the order of "degree." In terms of attacking power nodes, the index proposed in this paper has the same rate as "degree." Therefore, the proposed model can better describe the vulnerability of the power grid to withstand attacks. [ABSTRACT FROM AUTHOR]

The study on the scattering mechanism of breaking ship waves provides important theoretical basis to the ship detection and radar imaging in a marine environment. This paper presents a new procedure for evaluating the electromagnetic scattering field of breaking ship waves over a perfect electric conductor sea surface. In this paper, different forms of the near-field ship waves are obtained by the computational fluid dynamics (CFD) method, which provides a new means of analyzing a fully coupled fluid-structure interaction system in a detailed manner. Sufficient grids are used in the CFD numerical simulation to obtain the flow field information of the breaking waves. The accuracy of the breaking wave geometry has been improved obviously, which will lead to a better understanding of the electromagnetic scattering characteristics of breaking ship waves. Considering the multiple scattering between the ship hull and the breaking waves, the scattering field of the sea surface and the ship hull are evaluated by the forward–backward iterated physical optics algorithm. Both scattering characteristics of the breaking ship waves and distribution of the scattering coefficients are obtained. By comparing the bistatic scattering field in different situations, the numerical results show some important effects of the breaking ship waves, which are quite different from the effects of ship models. What is more, the time varying radar cross section of the breaking ship waves are presented based on the dynamic ship waves. [ABSTRACT FROM AUTHOR]

The paper presents a DSP-based design and control of a three-axis servo motion system that effectively divides control tasks between the master control terminal and four slave drives. The proposed architecture enhances the immediacy of platform positioning and the integration between software and hardware. The paper utilizes a high-accuracy encoder as a reference value for accuracy improvement and integrates firmware via the proposed embedded execution program, thereby reducing the accuracy error of the low-accuracy encoder. The main control core employs a digital signal processor (DSP) for input and output signal reading and writing, digital communication interface processing, and user interface. The slave controller utilizes four digital signal processors to accomplish servo position control in a digital way. The paper employs encoder calibration technology to upgrade the positioning accuracy of the surge axis. Finally, the paper validates the correctness and feasibility of the proposed method through experimental results from a set of adjustable experimental platforms of linear motion stroke and rotary motion stroke. In summary, the paper underscores the integration of hardware and software to attain high-precision and dependable control of the motion system. [ABSTRACT FROM AUTHOR]