Hasil untuk "Electricity and magnetism"

Feiyue Yan, Jiangjun Ruan, Yufei Liu et al.

ABSTRACT In this paper, a model‐aided state parameter inversion identification method based on the coil current (CC) of electromagnetic trip device (ETD) is proposed to realise the state parameter inversion online and the quantitative description of defects. Firstly, the inductance calculation model (ICM) considering flux saturation is established based on the magnetic circuit model, and the electromagnetic dynamic coupling model of ETD is constructed and the models are verified by experiments. Subsequently, the state parameter vector space, which can be used to describe the typical defect types is constructed, and the corresponding dataset is created by the electromagnetic dynamics model. Afterwards, the parameter inversion model with CC features as input and state parameter vector as output is obtained by the convolutional neural network (CNN). The accuracy of the parameter inversion model and the validity of the inversion method are verified. Compared with the traditional state classification method based on CC features, the state parameter inversion method proposed can realise the physical quantitative description of the mechanical state, has more explicit physical interpretability and provides a new way to conduct state evaluation and defect diagnosis.

Olanrewaju Lasabi, Mohamed Khan, Andrew Swanson et al.

The rapid integration of renewable energy sources has accelerated the adoption of DC microgrids as an effective platform for flexible and reliable power generation and management. However, conventional droop-based control suffers from inherent limitations, particularly voltage deviations at the DC bus, which compromise stability, power-sharing accuracy, and overall system performance. To address these challenges, this paper presents a distributed secondary control framework for a standalone PV battery-based DC microgrid that achieves bus voltage regulation, precise power distribution, and state-of-charge (SoC) balancing across multiple energy storage units (ESUs). At the primary level, an adaptive mechanism is introduced that dynamically adjusts droop coefficients in response to the real-time SoC of each ESU, promoting balanced utilization of storage resources. At the secondary level, the strategy leverages limited peer-to-peer communication to exchange only aggregate power information, thereby enabling accurate load sharing while preserving scalability and plug-and-play capability. The control architecture further incorporates voltage and current error compensation, with parameters tuned using a Whale Optimization Algorithm to enhance dynamic response. Validation is carried out through a real-time simulation environment developed in MATLAB/Simulink R2024b and executed on a Speedgoat^TM platform. The results demonstrate robust SoC equalization, improved bus voltage stability, and reliable cooperative coordination, positioning the scheme as a practical solution for next-generation DC microgrids.

Hui WANG, Yucheng DONG, Yuqi XIA et al.

To address the issues of low renewable energy accommodation rates, high carbon emissions, and poor operational economy in mining areas of Northwest China, this paper proposes an optimal scheduling model for coal mine integrated energy system (CMIES) that incorporates the mutual recognition of stepped carbon and green certificates, as well as gravity energy storage. Initially, the basic CMIES model was developed by considering the diverse utilization of mine resources, including coalbed methane and gravity energy storage of abandoned mines. Subsequently, to enhance the economic efficiency and energy utilization rate of the CMIES, coupling equipment such as carbon capture, power-to-gas, and combined cooling, heating, and power units was incorporated into the system. Additionally, a flexible load model for electricity, heat, and cooling was established to improve the system's operational flexibility. Furthermore, a mutual recognition mechanism for stepped carbon and green certificates was introduced to encourage the utilization of renewable energy equipment through market interactions. Finally, a mixed-integer programming model was formulated to minimize the total operating cost of the system and was solved using Cplex. The simulation results demonstrate that the proposed model significantly enhances the renewable energy accommodation rate in mining areas while reducing system carbon emissions, striking a balance with operational economics, thereby providing a theoretical foundation for the low-carbon and economically viable transition of CMIES.

Guanjun Wang, Xusheng Tang, Fengyi Huang et al.

ABSTRACT This paper proposes a polarisation‐insensitive absorptive metamaterial unit cell that achieves a perfect absorption of circularly polarised (CP) incident waves. To overcome the miniaturisation limitations inherent in conventional metamaterial designs, an innovative approach employing a sandwiched configuration with cladding layers is introduced. This approach approximates perfect electric conductor (PEC) boundary conditions, enabling the truncation of the bulky periodic structure into a one‐dimensional wall‐type absorptive metamaterial (WAM). To mitigate mutual coupling under stringent aperture constraints, four WAM screens are integrated concentrically around the central element of a compact five‐element array antenna featuring sub‐wavelength element spacing (0.4λ) at the GPS L1 frequency. Both simulations and experimental results demonstrate inter‐element mutual coupling suppression of less than −23 dB between the central and peripheral elements, alongside a peak realised gain improvement exceeding 3 dB for the central element. The WAM‐enhanced adaptive five‐element array achieves a maximum improvement of 4 dB in anti‐jamming capability.

Seong Joo Maeng, Suk-Jin Kim, Jung-Hwan Lim et al.

This paper analyzes the performance of the bistatic staring spotlight mode in a low-orbit satellite environment and then compares it with the performance of the monostatic staring spotlight mode. The staring spotlight mode provides high-resolution images by continuously stare at the target via azimuth beam steering. However, monostatic synthetic aperture radar (SAR) systems may not achieve the desired performance in this mode owing to the geometric limitations of performing missions using a single satellite. To overcome these limitations, a bistatic SAR system that uses two satellites is considered in this study. By using two satellites, uncertain ground structures can be handled with flexibility. Moreover, a strategically planned design for a bistatic SAR system can help achieve a wider range and better performance than a monostatic SAR system. By applying this design to the staring spotlight mode, a SAR system that offers both high-resolution images and good performance is proposed.

Jinyue Peng, Yuxuan Yang, Yang Zhang et al.

Large-size electronic-grade polycrystalline silicon is an important material in the semiconductor industry with broad application prospects. However, electronic-grade polycrystalline silicon has extremely high requirements for production technology and currently faces challenges such as carbon impurity breakdown, microstructure and composition nonuniformity and a lack of methods for preparing large-size mirror-like polycrystalline silicon samples. This paper innovatively uses physical methods such as wire cutting, mechanical grinding and ion thinning polishing to prepare large-size polycrystalline silicon samples that are clean, smooth, free from wear and have clear crystal defects. The material was characterized at both macroscopic and microscopic levels using metallographic microscopy, scanning electron microscopy (SEM) with backscattered electron diffraction (EBSD) techniques and scanning transmission electron microscopy (STEM). The crystal structure changes from single crystal silicon core to the surface of the bulk in the large-size polycrystalline silicon samples were revealed, providing a technical basis for optimizing and improving production processes.

Fengliang XU, Keqian WANG, Wenhao WANG et al.

With the high penetration rate of distributed photovoltaic access and the promotion of re-electrification and electrical energy substitution, the volatility of the system source and load is intensified, and the traditional distribution network planning methods are difficult to adapt to the requirements of the new power system development. To address this problem, an optimal allocation model for hybrid energy storage in low-voltage distribution networks considering incentive-based demand response is firstly established. Then, based on the characteristics of energy storage devices and incentive-based demand-side response resources at different time scales, it is proposed to use the improved VMD algorithm to make a multi-scale decomposition and combined reconstruction of the net load curves, and the improved whale optimization algorithm is used to solve the optimal allocation model with the objective of the minimum sum of the total system cost and active power fluctuation value. Finally, the effectiveness of the proposed scheme is verified with practical examples.

Jian GUAN, Ningbo LIU, Guoqing WANG et al.

Marine target detection and recognition depend on the characteristics of marine targets and sea clutter. Therefore, understanding the essential features of marine targets based on the measured data is crucial for advancing target detection and recognition technology. To address the issue of insufficient data on the scattering characteristics of marine targets, the Sea-Detecting Radar Data-Sharing Program (SDRDSP) was upgraded to obtain data on marine targets and their environment under different polarizations and sea states. This upgrade expanded the physical dimension of radar target observation and improved radar and auxiliary data acquisition capabilities. Furthermore, a dual-polarized multistate scattering characteristic dataset of marine targets was constructed, and the statistical distribution characteristics, time and space correlation, and Doppler spectrum were analyzed, supporting the data usage. In the future, the types and quantities of maritime targets will continue to accumulate, providing data support for improving marine target detection and recognition performance and intelligence.

Zezhou WANG, Mingming ZHANG, Fengqiang QIAN et al.

With increasing PV connected to MV distribution network, the problem of node voltage fluctuation and network loss is becoming more and more serious. Taking the communication conditions and calculation capabilities of MV distribution networks into account, a centralized regulation optimization strategy for distributed PV connected to MV distribution network is proposed to realize the suppression of voltage fluctuation and excessive network loss. Firstly, the impacts of PV integration on node voltage and network loss are analyzed. Then, a multi-objective optimal control model is established, with the power flow balance equation, node voltage, branch current and system operation as constrains, and with the minimal network loss, minimal voltage fluctuation and maximum consumption of DGs as objective. In addition, the commercial CPLEX is used to solve the model. Finally, the effectiveness of the proposed model is verified through case simulation. The results show that the proposed model can effectively reduce the voltage fluctuation and network loss, reasonably allocate the output of DGs and ensure the utilization of PV in a reasonable range.

A. Abramov, Y. Yue, V. Rumyantsev

The present work studied effects of transformation of refractive index periodicity on electromagnetic wave propagation through grating waveguides. In lieu of the standard refractive index periodicity, although its unit cell consists of two kinds of materials, we consider few such unit cells as a new supercell, where the material parameters in a standard unit cell are changed. It has been shown how by changing parameters of the periodicity to control the wavelength and intensity of resonant optical mode (guided mode resonance) arising inside grating area. High quality factor calculated for the specific angle of incidence and periodicity parameter. Thus, we demonstrated that transformation of refractive index provides additional tools of controlling the GMR, and that means the sample can be designed more functional in terms of real application.

Peng Wang, Chaofan Yu, Shakeel Akram et al.

Abstract Variation in air pressure severely affects the insulation of electric vehicle (EV) motors, hence weakening the reliability of EVs for safe operation. Nomex‐polyimide‐Nomex, a typical insulation material for EV motors, was used to investigate the motor insulation performance under different air pressures. The results show that the partial discharge inception voltage is significantly reduced for EV motors operated at lower air pressures, and the probability of partial discharge (PD) occurrence is increased. The macroscopic results reveal that the active area of the PD expands at low pressure, while the non‐corroded ring appears in the centre. Additionally, although the number and amplitude of the PD increase significantly with decrease in air pressure, the active area of the PD expands and electrical stress on the insulation per unit area increases slowly. Therefore, when the pressure decreased from 60 to 40 kPa, the endurance life does not show a significant downward trend. Furthermore, the dielectric constant and loss of the low‐pressure samples significantly change during the ageing process, which further indicates critical degradation of the insulation. The aforementioned investigations reveal that the air pressure at different altitudes has a significant impact on the performance of insulation materials.

A. Kade, Supriyatman Supriyatman, Darsikin Darsikin et al.

This research is based on the behavior of students who are confused about explaining a natural phenomenon when taking electricity and magnetism courses. The covid-19 pandemic, which requires online courses, adds to the problems in improving the quality of learning in electricity and magnetism courses. As prospective teachers, physics education students with low concept mastery are certainly very concerned because they will teach it to their students. So this research aims to identify difficulties and recommendations for learning electricity and magnetism. The qualitative descriptive method is used to obtain a description of the problem, and obtain recommendations for effective and efficient learning. Learning is done online through zoom meetings and LMS.fkip.untad.ac.id. Data was collected by testing the mastery of the concept of electricity and magnetism. The test was given online to 40 students and interviews with 5 students as respondents. The results showed that the biggest difficulty of students in applying the concept of the potential vector was about 70%, analysis on the application of Ampere's law was about 47.5%, applying the concept of the field in a cylinder about 30%, and applying the Biot-Savart law was about 25%. It can be concluded that there are still many students who have difficulty mastering the concepts of electricity and magnetism after participating in online learning

Johnatan M. Rodríguez‐Serna, Ricardo Albarracín‐Sánchez

Abstract Electrical trees are defects originated and driven by partial discharges (PD) activity and this is the reason why their modelling and simulation are fundamental for the ageing mechanisms comprehension and diagnosis analyses of insulation systems compound by solid dielectrics. This study presents a brief review of the different models implemented to simulate PD in electrical trees inside solid dielectrics. In addition, an improved deterministic model as well as a stochastic model are presented, which allow predicting adequately the PD pulses distribution, in magnitudes and phase, for non‐conducting electrical trees of different shape and length. Two case studies were simulated and their results exhibit good agreement when compared with measurements presented in the literature. It is concluded that the main parameters that state the PD behaviour in trees are the inception and extinction voltage magnitudes, including their probability distributions, and the tree geometry. The models can be used for prognosis analysis based on on‐line measurements.

Ke XIONG, Ruichen ZHANG, Rui WANG et al.

As a combination of the Internet of Things and the smart grid, the Electricity Internet of Things (EIoT) could effectively integrate various communication resources and power resources to improve the informatization level of the power grid and the utilization of existing equipment. The EIoT would be a typical example of the Smart Energy Internet, which enjoys the features of comprehensive perception, efficient response, and flexible processing. The fifth-generation mobile communication network (5G) has the characteristics of "high rate, high capacity, high reliability, low latency and low energy consumption". The key technologies of 5G can satisfy the power grid requirements of "mass equipment access, mass power data transmission, power grid reliability, flexible cooperative response, and long equipment life". In this work, the basic concept of EIoT is presented. Then, the overall structure of EIoT based on 5G is constructed. Next, the 5G applications and its key technologies in EIoT are summarized. Finally, future research directions on 5G technology and EIoT are discussed.

He WANG, Yujia LI, Zhongdong YIN et al.

When multiple active power filters (APF) are incorporated into the regional distribution network, there are complex negative interaction effects among the control circuits, resulting in the decline of APF compensation performance and harm to the stability of power system. Firstly, a multi-APF grid-connected mathematical model under the condition of weak power grid is established based on NORTON equivalent circuit. And then, combined with the dynamic relative gain array (DRGA) principle, a quantitative analytical method is proposed for analyzing the interaction degree between multiple APF control circuits, which can analyze the quantitative relationship between the interaction degree, the control circuit parameters and the weak grid equivalent inductance based on different frequency intervals. Finally, the MATLAB/Simulink platform is used to build a grid-connected simulation system model. The time-domain simulation results are consistent with the theoretical analysis, which verifies the effectiveness of the proposed method.

Rosivaldo Carvalho Gama Junior, Ítalo Gabriel Neide

This work addresses the teaching of the indissociation of electricity and magnetism through the integration of experimental and computational activities. This paper is part of a professional master's study in teaching exact sciences, from the University of Vale do Taquari. The study was carried out at the University of the State of Amapá, municipality of Macapá. The objective of this research is to reflect about results obtained in the sequences of practical activities developed with academics from the 4th semester of the Natural Sciences Degree course through the integration of experimental and computational activities in the context with indissociation of electricity and magnetism. The research developed has a qualitative nature. For data collection and analysis, POE guides were applied during the development of pedagogical activities with the use of experimental and computational activities. The results of the experimental and computational activities showed the possibility of its integration, since academics were able to have a non-linear and holistic view of the indissociation of electricity and magnetism and a better understanding of the more specific contents of electromagnetism. It is concluded that the experimental activities and the computational activities aroused the interest, provided the social and intellectual interaction of the students.

Irina D. Yushina, Fedor V. Podgornov, Maxim Gavrilyak et al.

The dielectric properties of tetramethylammonium monoiodide and pentaiodide were investigated in broad temperature range (−150∘C till +50∘C). It was demonstrated that the structural organization of the polyiodide chain containing I…I charge-assisted halogen bonds influenced the parameters and the mechanism of electric conductivity of considered compound. The impedance spectroscopic measurements revealed that the direct current electric conductivity of pentaiodide salt is around four orders of magnitude higher than that of corresponding monoiodide. Moreover, pentaiodide demonstrates the hopping mechanism of conductivity.

Yawen Liu, Q. Ma, Yang Ming et al.

Bian XingMing, Zhu JunYu, Zhu JunYu et al.

The corona-generated space charge may vary in different air pressures, and the quantitative law between the corona-generated space charge density and air pressure has never been investigated. This work utilised computational approaches to explore the role of air pressure in the variation of negative corona-generated space charge. A negative fluid model in which the air pressure could be varied was built up to calculate the charged-particle density and electric field under different applied voltages. The continuity equations were solved by flux corrected transport algorithm and the Poisson equation was computed by the successive over relaxation method. The variations of important parameters due to air pressure were analysed. The particles densities of electrons, positive ions and negative ions at standard and low atmosphere pressures were computed, which increased markedly due to the decrease of atmosphere pressure. At fixed applied voltages, the exponential decay law between the maximal values of electron/positive ion densities at the head of the streamer and air pressure could be obtained. The quantitative law between the maximal values of electron/positive ion densities at the head of the streamer and the applied voltage, relative air density was also achieved.

Lin Ding, R. Chabay, B. Sherwood et al.

The Brief Electricity and Magnetism Assessment (BEMA), developed by Chabay and Sherwood, was designed to assess student understanding of basic electricity and magnetism concepts covered in college-level calculus-based introductory physics courses. To evaluate the reliability and discriminatory power of this assessment tool, we performed statistical tests focusing both on item analyses (item difficulty index, item discrimination index, and item point biserial coefficient) and on the entire test (test reliability and Ferguson's delta). The results indicate that BEMA is a reliable assessment tool.