Hasil untuk "Electricity and magnetism"

Keyun LI, Ning ZHANG, Le ZHAO et al.

Under “dual-carbon” goals, the carbon emission accounting for power transmission and transformation projects can provide important data reference for carbon reduction of power projects. At the present stage, the field of carbon emission accounting in power transmission and transformation projects is facing the problems including the lack of standards and weak research foundation, thus it is significant to establish specific methodology and models. This paper is oriented to the application scenario of upstream carbon reduction in the supply chain of power transmission and transformation projects. Firstly, the paper defines the scope of carbon emission accounting from perspectives of carbon accounting objects and system boundary; secondly, the paper analyzes the carbon emission activities of key equipment and materials during raw material acquisition and manufacturing stages, researches the way of collecting and converting activity data with limited raw data from the pre-engineering stage, and constructs carbon emission accounting models for key equipment and materials in power transmission and transformation projects; finally, the paper conducts a case study for an ultra-high voltage direct current transmission and transformation project, and calculates the carbon emissions of seven key electric equipment and materials during raw material acquisition and manufacturing stages based on the limited data sources from the preliminary design stage. The research results show that wires, tower materials and transformers are the main components of the total carbon emissions, thus it is essential to focus on carbon emissions of the equipment, and promote the research on carbon reduction in electrical equipment and materials.

Xiaoyu LAN, Jiyan HU, Mingshen LIANG et al.

Aiming to address the problem of increased radar jamming in complex electromagnetic environments and the difficulty of accurately estimating the target signal close to a strong jamming signal, this paper proposes a sparse Direction of Arrival (DOA) estimation method based on Riemann averaging under strong intermittent jamming. First, under the extended coprime array data model, the Riemann averaging is introduced to suppress the jamming signal by leveraging the property that the target signal is continuously active while the strong jamming signal is intermittently active. Then, the covariance matrix of the processed data is vectorized to obtain virtual array reception data. Finally, the sparse iterative covariance-based estimation method, which is used for estimating the DOA under strong intermittent interference, is employed in the virtual domain to reconstruct the sparse signal and estimate the DOA of the target signal. The simulation results show that the method can provide highly accurate DOA estimation for weak target signals whose angles are closely adjacent to strong interference signals when the number of signal sources is unknown. Compared with existing subspace algorithms and sparse reconstruction class algorithms, the proposed algorithm has higher estimation accuracy and angular resolution at a smaller number of snapshots, as well as a lower signal-to-noise ratio.

Shanshan ZHAO, Fei Gao, Yajie LI et al.

To fully leverage the coordination control of the soft open point (SOP) for distributed power generation, electric vehicles, energy storage, and other diversified micro groups, this paper investigates the coordinated optimization control strategy for flexible distribution networks with microgrid groups. The functions of different types of SOP access and the operation control modes of S are analyzed. Considering the load balancing and peak-valley shifting effects of SOP access and the economy of power grid operation, a multi-objective optimization model with the minimization of load variance, load rate variance, and active power network loss is established. Considering the complexity of the flexible distribution network, an improved memetic algorithm is proposed to solve the multiobjective optimization problem. Through simulation verification, it can be known that the proposed optimization model can reduce network loss and balance load by controlling SOP.

Yang Zhou, Yongzhong Zhu, Xiaoyu Liu et al.

ABSTRACT This paper proposes a novel phased array which has outstanding advantage of broadband, miniaturisation and wide‐angle scanning. First, leveraging a conventional antipodal Vivaldi structure enhanced with microstrip line side‐feeding, resistive loading techniques and top‐loaded radiating patches. Then, wide‐angle impedance matching and stable scanning performance are realised by incorporating a dielectric matching layer above the radiating element and introducing dummy elements at the array edges. Additionally, elliptical parasitic patches are integrated to suppress gain fluctuations during beam scanning. Finally, a miniaturised 6 × 10 finite array is fabricated and measured. Both simulated and measured results indicate that the array maintains an active voltage standing wave ratio (VSWR) below 2.5 across a 4:1 bandwidth (2.1–8.4 GHz), supporting scan coverage up to ± 60° in the E‐plane and ± 50° in the H‐plane. The gain fluctuations at key frequencies is constrained within 3 dB throughout the scan range. Therefore, the design achieves a comprehensive property of low cost, compact size, ultra‐wideband operation, wide‐angle impedance matching and wide‐angle scanning. This design demonstrates great potential for space‐constrained applications, particularly in airborne multifunction radar systems.

Chung-Tao Chou, Eugene Park, Josep Ingla-Aynes et al.

A spin version of transistor, where magnetism is used to influence electrical behaviors of the semiconductor, has been a long-pursued device concept in spintronics. In this work, we experimentally study a field-effect transistor with CrSBr, a van der Waals (vdW) antiferromagnetic semiconductor, as the channel material. Unlike the weak magnetic tunability of in-plane currents previously reported in vdW magnets, the channel current of our transistor is efficiently tuned by both gate voltage and magnetic transitions, achieving a magnetoresistance ratio as high as 1500%. Combining measurement and theoretical modeling, we reveal magnetically modulated carrier concentration as the origin of the large magnetoresistance. The strategy of using both magnetic ordering and electric field in the same device to control ON/OFF states of a transistor opens a new avenue of energy-efficient spintronics for memory, logic and magnetic sensing applications.

Yousef Alharbi, Ahmed Darwish, Xiandong Ma

Mismatched power generation is a serious issue in PV systems, resulting from unequal power generation between PV components. Solutions have been proposed to reduce or eliminate the mismatch concern. One practical strategy is individually harvesting the maximum power from each PV component; the more distributed MPPT is applied to a finer level, the more power can be obtained. This study proposes three-input single-output boost converters that are employed to effectively increase PV power generation and significantly reduce mismatch issues between the PV submodule (PV SM). Each boost converter will be controlled to harvest the maximum power from a group of PV cells inside a single PV module. The outputs of the three boost converters are connected in series to provide higher output voltage for grid integration. The cascaded power converters are linked with a forwarding diode to provide a protection feature for the system and prevent the reverse current from harming the PV module. On the grid side, a single-phase Voltage Source Inverter (VSI) is used to convert the DC power from the PV module to sinusoidal AC power. The performance of the suggested inverter has been confirmed through experimental tests.

Qi Yuan, Tingting Sun, Bo Tang et al.

Abstract The authors present the design of a rectangular micro‐coaxial line (RMCL) to ground‐to‐ground (GSG) probe pad transition for broadband millimetre‐wave (mmW) probe testing. The proposed transition is designed to effectively operate across the frequency range from DC to 170 GHz, providing the capability to convert non‐50 Ω RMCL ports to 50 Ω GSG ports. To validate the design methodology, the back‐to‐back model of the transition is fabricated and experimentally characterised. The fabricated transition exhibits a remarkable return loss exceeding 18 dB, along with an insertion loss below 0.4 dB within the frequency span of 0–75 GHz. With this transition, on‐chip measurement of non‐50 Ω ultra‐wideband millimetre‐wave chips becomes feasible.

Gauthier Philippe, Mathieu Moalic, Jarosław W. Kłos

We demonstrate that the spin wave Cherenkov effect can be used to design the unidirectional spin wave emitter with tunable frequency and switchable direction of emission. In our numerical studies, we propose to use a pair of traveling profiles of the magnetic field which generate the spin waves, for sufficiently large velocity of their motion. In the considered system, the spin waves of shorter (longer) wavelengths are induced at the front (back) of the moving profiles and interfere constructively or destructively, depending on the velocity of the profiles. Moreover, we showed that the spin waves can be confined between the pair of traveling profiles of the magnetic field. This work opens the perspectives for the experimental studies in hybrid magnonic-superconducting systems where the magnetic vortices in a superconductor can be used as moving sources of the magnetic field driving the spin waves in the ferromagnetic subsystem.

Manh-Huong Phan

The recent discovery of two-dimensional (2D) van der Waals (vdW) magnetic materials has provided new, unprecedented opportunities for both fundamental science and technological applications. Unlike three-dimensional (3D) magnetic systems, the electric manipulation of vdW magnetism (e.g., magnetization state, magnetic anisotropy, magnetic ordering temperature) down to the monolayer limit at ambient conditions enables high efficiency operation and low energy consumption, which has the potential to revolutionize the fields of spintronics, spin-caloritronics, and valleytronics. This article provides an in-depth analysis of the recent progress, emerging opportunities, and technical challenges in the electric manipulation of magnetic functionalities of a wide variety of 2D vdW magnetic systems ranging from metals to semiconductors and heterostructures. The state-of-the-art understanding of the mechanisms behind the electric modulation of magnetism in these 2D vdW magnetic systems will drive future research towards novel applications in spintronics, spin-caloritronics, valleytronics, and quantum computation.

A. Métioui

Magnetism is omnipresent in multiple natural and constructed phenomena we interact with daily. However, few students knew about the different explanations advanced relative to this mysterious magnetic force imperceptible by our senses before the advent of the discovery of the atomic and molecular aspects of matter. Unfortunately, the concepts associated with the study of magnetism presented in many textbooks do not consider the conceptual difficulties encountered by scientists and the false theories developed and abandoned following new experiments and theories. Towards the end of the 18th century, with the developments of classical physics, among others in mechanics, electrostatic, electricity, and measuring instruments, scientists pierced the secret of the magnet stone and the compass used in navigation for several centuries BC. On the other hand, the progress made in studying matter at the atomic scale at the beginning of the 20th century made it possible to explore the phenomenon of magnetism in greater depth and give it a quantum interpretation. It is impossible to present all the conceptual complexity concerning the development of magnetism in a few pages. Thus, we will limit to synthesizing the most discoveries related to magnetism from the ancient time, five centuries before Jesus Christ, to the beginning of the 20th century. Thus, we will mainly focus on the erroneous theories developed throughout history by renowned scientists and the conceptual difficulties related to the study of magnetism.

Bo Lin, Chijie Zhuang

Abstract Recently, a new framework to compute the photoionisation rate in streamer discharges accurately and efficiently using the integral model and the fast multipole method (FMM) was presented. This paper further improves the efficiency of this framework with adaptive strategies. The adaptive strategies are based on the magnitude of radiation and the electric field during the streamer propagation, and are applied to the selection of the source and target points. The accuracy and efficiency of this adaptive FMM are studied quantitatively for different domain sizes, pressures and adaptive criteria, in comparison with some existing efficient approaches to compute the photoionisation. It is shown that appropriate adaptive strategies reduce the calculation time of the FMM greatly, and maintain the high accuracy that the numerical error is still much smaller than other methods based on partial differential equations. The performance of the proposed adaptive method is also studied for a three‐dimensional positive streamer interacting problem with a plasma cloud, which shows that the FMM with proper adaptive strategies is even faster than the partial differential equation based methods with efficient boundary conditions for the ionisation calculation.

Guodong HAN, Peirong JI, Fei WANG

Considering the distributed market transaction mode, this paper proposes a two-layer optimization model that considers the coordination of optical storage and user load adjustment. Based on the transfer relationship between distribution network companies and optical storage investors, this paper proposes a market framework for distributed transactions. The market transaction model and solution algorithm are established, and the feasibility of the proposed method is verified based on the simulation example of the IEEE 33 bus distribution network system.

Quanliang Cao, Liangyu Xia, Xian Li et al.

Abstract Coil design and performance analysis are critical for the electromagnetic forming (EMF) process. However, previous studies have paid little attention to the coil conductivity, and the influence of eddy current effects in coil conductors on the forming process has not been well understood. This work aims to address these problems through numerical and experimental investigations. It is found that, due to the eddy current effects, the uneven current distribution appears in the coil conductors that should be considered when analysing the forming process, especially for the cases with large heights of coil conductors. Meanwhile, an important and interesting discovery is that the eddy current effects can greatly reduce the sensitivity of the coil conductivity with respect to the workpiece deformation, the Joule heating and the temperature rise in the coil. For instance, compared to a forming system with a copper coil, the forming height of the workpiece in the forming system with an AA5083‐O coil is reduced by less than 5 % under the same discharge energy, while the copper conductivity is 3.3 times that of the latter. These results are helpful to understand the EMF process and achieve the optimal design of coils.

A. V. Zarubin, F. A. Kassan-Ogly

In this paper, the frustration properties of the Ising model on a one-dimensional monoatomic equidistant lattice in an external magnetic field are investigated, taking into account the exchange interactions of atomic spins at the sites of the first, second, and third neighbors. Exact analytical expressions for the thermodynamic functions of the system are obtained by the Kramers--Wannier transfer-matrix method. A magnetic phase diagram of the ground state of such a spin system is constructed and studied thoroughly. The points and lines of frustrations of the system depending on the values and signs of exchange interactions and on an external magnetic field are found. The criteria for the occurrence of magnetic frustrations in the presence of competition between the energies of exchange interactions and an external magnetic field are formulated. The peculiar features are investigated and the values of entropy and magnetization of the ground state of this model are obtained in the frustration regime and beyond it. Various types of behavior of entropy, magnetization, and magnetic susceptibility depending on the model parameters are revealed.

Lena J-T Strömberg

Electro-magnetism for components and pot plants in interaction are studied with experiments and analysis. Experiments were done using a chamber for heat energy transduction in arrangements with battery electrodes in a pot. The process required heat to produce current and electric power together with the battery. This study also considered the performance in terms of more current and voltage. The largest device produced 0.16 mW. The function of the chamber is considered chamber amplification. This study also analyzed with Hamiltonian mechanics. An application outdoor was also presented to replace and understand the summer energy sources with electricity. By using this procedure, this study found that if a plant adapts, it develops durability of cold outside

Chenxi Zhao, Chong Xiao

Yanchun XU, Caicai ZHAO, Sihan SUN et al.

In view of the characteristics of distribution network with large-scale integration of distributed generation when single-phase grounding fault occurs, such as complex structure and operation mode, obscure electrical quantity after fault, weak fault characteristics and so on, this paper proposes a new fault location method for active distribution network based on improved local mean decomposition (ILMD) and energy relative entropy. Firstly, the mirror extension is used to extend the signals at both ends to eliminate the endpoint effect of LMD. At the same time, the adaptive noise is added to the signal to overcome the mode aliasing problem of LMD, and the ILMD is used to decompose the transient zero sequence current of each section. Then the energy relative entropy of all product functions (PF) after decomposition is calculated. The sum of relative energy entropy of all PF components is the relative energy entropy between sections. The fault section is judged by the positioning criteria set in this paper. Simulation results show that the proposed algorithm has high accuracy in fault location for 10 kV small current grounding system and improved IEEE 33 node system under different simulation conditions, which verifies the accuracy of the proposed method.

Feng LI, Huimin PENG, Huling YUAN et al.

Due to the lack of guide tools for UPFC real-time operation optimization, the powerful power flow control capability of UPFC cannot be played flexibly. An UPFC operation optimization decision-making application function is designed based on the smart grid dispatching control system. According to the power flow calculation characteristics of UPFC project under actual quota working mode, the sensitivity of the UPFC control measures is solved. Parallel computing of the UPFC multi-control target set is carried out using the rich online computing resources, and the UPFC static security control measures and power flow optimization control measures are obtained. The designed application function makes full use of the UPFC control capability to improve the flexibility of power grid operation, and provides decision-making support for dispatching operators. The calculation process for UPFC online operation optimization is illustrated through a case study of the 500 kV UPFC project of Suzhou southern power grid. The results show that the proposed method can effectively solve the static security problem of the region near UPFC and optimize the near region network loss.

Sabah Ibrahim Wais, Pirzheen Ageed Mohammed

The behavior of corona discharge was investigated in wire–cylinder electrodes under the effect of a crossed magnetic field. Townsend’s formula was used commonly with a modified empirical formula to evaluate the different parameters of corona discharge in positive and negative discharge. By using a least-squares fitting, the dimensional constants A, K, and the exponent n displayed a significant dependence on the applied magnetic field. An improvement of pre-breakdown has been achieved by using a crossed magnetic field. For both polarities, while the magnetic field is present, breakdown voltage V_B and corona inception voltage V₀ increased, whereas the corona current decreases. In addition, the corona inception voltage was greater in positive corona in the absence of a magnetic field, while the opposite occurred regarding the crossed magnetic field. Furthermore, the breakdown streamer demonstrated significant triggering in the negative corona by applying the magnetic field.

Xueyou HUANG, Jun XIONG, Yu ZHANG et al.

The traditional switchgear partial discharge pattern recognition methods lack certain generalization performance and have low recognition accuracy, so it is hard to apply them in practical engineering. A method for switchgear partial discharge pattern recognition based on residual convolutional neural network is proposed. A residual module is added to the network to solve the degradation problem after accuracy saturation caused by the deepening of network layer number, and the shallow and deep feature fusion learning of switchgear partial discharge data is integrated to achieve the pattern recognition. Based on the partial discharge simulation experiments of different insulation defect categories of switchgears and the field testing of distribution stations, a sample database of switchgear partial discharge data is constructed, and experimental analysis is conducted. The experimental results show that the recognition correct rate of the proposed method reaches 96.06%, at least 20.22% higher than that of the traditional recognition methods, and the recognition rate can be improved more with the increase of the number of samples in the training set. Through integrated use of the feature layer fusion module and residual module, the proposed model is significantly improved in the generalization performance and is more suitable for practical engineering.