Electromagnetic Model Research Articles

Automated shot-to-shot optimization of the plasma start-up scenario in the TCV tokamak

Plasma start-up is typically achieved manipulating poloidal magnetic fields, gas injection and possibly auxiliary heating. Model-based design techniques have been gaining increasing attention in view of future large tokamaks which have more stringent constraints and less room for trial-and-error. In this paper, we formulate the tokamak start-up scenario design problem as a constrained optimization problem and introduce a novel shot-to-shot correction algorithm, based on the Iterative Learning Control concept, to compensate for unavoidable modeling errors based on experimental data. The effectiveness of the approach is demonstrated in experiments on the TCV tokamak showing that the target ramp-up scenario could be obtained in a small number of shots with a rough electromagnetic model.

Droop Frequency Limit Control and Its Parameter Optimization in VSC-HVDC Interconnected Power Grids

With the gradual emergence of trends such as the asynchronous interconnection of power grids and the increasing penetration of renewable energy, the issues of ultra-low-frequency oscillations and low-frequency stability in power grids have become more prominent, posing serious challenges to the safety and stability of systems. The voltage-source converter-based HVDC (VSC-HVDC) interconnection is an effective solution to the frequency stability problems faced by regional power grids. VSC-HVDC can participate in system frequency stability control through a frequency limit controller (FLC). This paper first analyses the basic principles of how VSC-HVDC participates in system frequency stability control. Then, in response to the frequency stability control requirements of the sending and receiving power systems, a droop FLC strategy is designed. Furthermore, a multi-objective optimization method for the parameters of the droop FLC is proposed. Finally, a large-scale electromagnetic transient simulation model of the VSC-HVDC interconnected power system is constructed to verify the effectiveness of the proposed droop FLC method.

Simulation analysis of overvoltage caused by grounded short circuit in the collection system of far-offshore wind farms

Abstract As the distance from the shore of offshore wind farms increases, MMC-HVDC technology is gradually gaining attention in its grid connection schemes. A broadband electromagnetic transient model of offshore wind farms with a total capacity of 800 MW connected to the grid via a flexible direct current transmission system is developed. After three types of grounded short circuit faults occur at different fault positions within the power collection system, the characteristics of overvoltage are obtained and they are analyzed on the basis of considering the low voltage ride-through capability of the direct-drive permanent magnet wind power generator. Combining the two factors of range and amplitude, the results show that the overvoltage phenomenon is the most serious when a two-phase grounded short circuit occurs at the converging busbar, which can be the focus of the study when setting up overvoltage protection.

Black-box modeling of PMSG-based wind energy conversion systems based on neural ODEs

Abstract Integrating renewable energy sources like wind power into the power grid enhances the dynamic interactions among renewable energy-producing equipment, leading to new technological issues for the power grid. Modeling and simulation are essential to ensure the stability of the emerging power grid, but they require precise dynamic component modeling, which is often unavailable due to technical confidentiality and other factors. Conventional hardware-in-the-loop (HIL) simulation can accurately simulate the dynamics of a single renewable energy device, but not the complex dynamics of multiple devices. This research introduces a method that combines classical mechanism modeling and differential neural network modeling to create accurate wind turbine models utilizing equipment measurement data or HIL simulation data. A realistic wind turbine electromagnetic transient simulation model of a specific type is developed and validated by connecting it to the IEEE-39 node system, confirming the model’s accuracy.

Research on the impact of train speed on the uplink performance of balise transmission system

Abstract In the CTCS system, the balise plays an important role in supporting the normal operation of trains. Based on this, this article studies the performance of the uplink of the balise transmission system under different speed conditions from three perspectives: theory, simulation, and measurement. Based on an in-depth analysis of the energy and data transmission process between the vehicle antenna and the ground balise, relevant electromagnetic theoretical models such as the input and output characteristics of the balise and the antenna magnetic field distribution are established. An electromagnetic field model of the balise transmission system is established using Maxwell software, and the simulation results are obtained. An experimental environment is built using responder products and the simulation results are analyzed. Methods are explored to improve the adaptability of responder transmission systems under high-speed operating conditions.

Broadband Terahertz Characterization and Electromagnetic Models for Fishnet Metasurfaces: From the Homogenization to the Resonant Regime

Broadband Terahertz Characterization and Electromagnetic Models for Fishnet Metasurfaces: From the Homogenization to the Resonant Regime

The damping factor improved the algorithm in semi-airborne transient electromagnetic modelling based on accelerated FDTD

3D modelling plays a crucial role in analysing semi-airborne transient electromagnetic fields, how to accurately and efficiently calculate electromagnetic response has become a significant issue. In this paper, a damping factor improved algorithm of the accelerated finite difference time domain (AFDTD) is proposed for semi-airborne transient electromagnetic modelling. Differing from the previous research, we introduce a novel function to redefine the damping factor, allowing for adaptive adjustment and enhancing calculation accuracy within the finite difference time domain (FDTD) iterative process. To verify the effectiveness of our approach, we conduct tests using homogeneous half-space models, which demonstrate that the improved damping factor significantly enhances calculation accuracy without a notable reduction in efficiency. Furthermore, we apply our improvement to typical conductivity models and polarisable conductivity models, and the results indicate that our approach achieves high accuracy in accelerated semi-airborne transient electromagnetic modelling.

Temperature Is Likely an Important Omission in Interpreting Vegetation Optical Depth

AbstractVegetation optical depth (VOD) satellite microwave retrievals provide significant insights into vegetation water content and responses to hydroclimatic changes. While VOD variations are commonly linked to dry biomass and live fuel moisture content (LFMC), the impact of canopy temperature (Tc) remains overlooked in large‐scale studies. Here, we investigated the impact of Tc on L‐band (1.4 GHz) and X‐band (10.7 GHz) VOD at diurnal and seasonal timescales. Synthetic benchmark VOD was created using realistic fields of Tc, LFMC, and biomass in an electromagnetic model. Perturbation experiments revealed that Tc strongly affects diurnal VOD variations at both L‐band and X‐band. Seasonally, while biomass emerges as the largest contributor to VOD variations in 70% (at X‐band) and 90% (at L‐band) of our study region, Tc and LFMC still play substantial roles. The findings stress the importance of refining retrieval algorithms to distinguish Tc, LFMC, and biomass effects for future VOD applications in ecohydrology.

Aggregate data‐driven dynamic modeling of active distribution networks with DERs for voltage stability studies

AbstractElectric distribution networks increasingly host distributed energy resources based on power electronic converter (PEC) toward active distribution networks (ADN). Despite advances in computational capabilities, electromagnetic transient models are limited in scalability because of their reliance on exact data about the distribution system and each of its components. Similarly, the use of the DER_A model, which is intended to examine the combined dynamic behavior of many DERs, is limited by the difficulty in parameterization. There is a need for improved dynamic models of DERs for use in large power system simulations for stability analysis. This paper proposes an aggregate model‐free, data‐driven approach for deriving a dynamic partitioned model (DPM) of ADNs. Detailed residential distribution feeders were first developed, including PEC‐based DERs and composite load models (CMLDs), from which the aggregated DPM was derived. The performance was evaluated through various case studies and validated against the detailed ADN model and state‐of‐the‐art DER_A model with CMLD. The data‐driven DPM achieved a of over 90%, accurately representing the aggregated dynamic behavior of ADNs. Furthermore, the DPM significantly accelerated the simulation process with a computational speedup of 68 times compared to the detailed ADN and a 3.5 times speedup compared to the DER_A CMLD model.

Optimization Design of Cogging Torque for Electric Power Steering Motors

Excessive cogging torque can cause torque fluctuations, noise, and vibration in electric power steering (EPS) motors, which is a key factor in the high-precision and high-performance optimization design of EPS motors for electric vehicles. This article takes a 12-slot 10-pole electric power steering motor for a certain car as an example. By establishing the corresponding electromagnetic field model and theoretical analysis of the motor, the influence of the pole arc coefficient and eccentricity parameters of the permanent magnet on the cogging torque of the electric power steering motor is explored. A comprehensive optimization scheme for reducing the cogging torque of the motor structure is proposed. The effectiveness of the designed scheme was verified through finite-element simulation and experimental testing of motor electromagnetism. Compared with the original design, the optimized structure of the EPS motor resulted in an 86.62% reduction in cogging torque during experimental testing.

LibEMMI_MGFD: A program of marine controlled-source electromagnetic modelling and inversion using frequency-domain multigrid solver

We develop a software package libEMMI_MGFD for 3D frequency-domain marine controlled-source electromagnetic (CSEM) modelling and inversion. It is the first open-source C program tailored for geometrical multigrid (GMG) CSEM simulation. An volumetric anisotropic averaging scheme has been employed to compute effective medium for modelling over uniform and nonuniform grid. The computing coordinate is aligned with acquisition geometry by rotation with the azimuth and dip angles, facilitating the injection of the source and the extraction of data with arbitrary orientations. Efficient nonlinear optimization is achieved using quasi-Newton scheme assisted with bisection backtracking line search. In constructing the modularized Maxwell solver and evaluating the misfit and gradient for 3D CSEM inversion, the reverse communication technique is the key to the compaction of the software while maintaining the computational performance. A number of numeric tests demonstrate the efficiency of the modelling while preserving the solution accuracy. A 3D marine CSEM inversion example has been examined for resistivity imaging. Program summaryProgram Title: libEMMI_MGFDCPC Library link to program files:https://doi.org/10.17632/mpk7xrd38m.1Developer's repository link:https://github.com/yangpl/libEMMI_MGFDLicensing provisions: GNU General Public License v3.0Programming language: C, ShellSoftware dependencies: MPI [1]Nature of problem: 3D Controlled-source electromagnetic modelling and inversion.Solution method: Frequency-domain modelling on staggered grid; Geometrical multigrid (GMG) method as an iterative solver; Quasi-Newton method for nonlinear minimization; Bisection-based backtracking line search.

Ways to overcome the barrier during the transition of asynchronous motors to the energy efficiency class IE5

Purpose. To provide a comprehensive analytical review on ways to increase the energy efficiency of induction motors and identify those suitable for transitioning fixed speed induction motors to IE5 level. Methodology. A thorough study of research and development in the field of increasing the energy efficiency of induction motors for various purposes was conducted. The experience of the development of traction induction motors of electric vehicles as dynamically developing is extrapolated. Results. It was established that the main limiting factor in increasing the energy efficiency of induction motors to the IE5 level is its thermal state. Analysis of ways to improve the efficiency of induction motors indicates the need for their complex application. It is most expedient to optimize and improve the elements of the air-cooling system of induction motors. To carry out the research, it is necessary to comprehensively apply electromagnetic and temperature field modeling systems of induction motors. Given certain shortcomings of thermal models of induction motors, it is necessary to combine modeling with experimental studies using both classical temperature sensors and the method of thermography. Originality. The combination of modern methods of modeling the thermal state of induction motors and experimental studies makes it possible to determine reserves for increasing the efficiency of existing motors. Using these results, it is possible to improve induction motors to the IE5 efficiency level. Practical value. Manufacturers and researchers see difficulties with the transition of induction motors of industrial purpose to the IE5 efficiency level, so they focused their attention on synchronous electric motors. The results of our research prove that, despite certain barriers, this transition can be made, albeit with certain difficulties.

Adaptive Internal Model Backstepping Control for a Class of Second-Order Electromagnetic Micromirror with Output Performance Constraints and Anomaly Control.

This paper investigates the asymptotic tracking problem for a class of second-order electromagnetic micromirror model with output performance constraints and anomaly control, which is subject to model parameter uncertainties and external disturbances. Specifically, this paper formulates the trajectory tracking control problem of an electromagnetic micromirror as a closed-loop control trajectory tracking problem based on the general solution framework of output regulation. Moreover, the extended internal model is introduced to reformulate the closed-loop control problem into a state stabilization problem of the augmented system. Based on the augmented system, an internal model backstepping controller is proposed by integrating the barrier Lyapunov Functions (BLF) and the Nussbaum gain function with the backstepping structure.This controller not only satisfies the output performance constraints of the micromirror, but also maintains the control performance in anomalous control situations. The final performance simulation demonstrates the efficacy of the proposed controller.

Transmissive and reflective type multi-nanolayer electro-optical modulators for chip-to-chip free space optical interconnection: wavelength-scale electromagnetic modelling by the method of single expression

Transmissive and reflective type multi-nanolayer electro-optical modulators for chip-to-chip free space optical interconnection: wavelength-scale electromagnetic modelling by the method of single expression

Changes of in vivo electrical conductivity in the brain and torso related to age, fat fraction and sex using MRI

This work was inspired by the observation that a majority of MR-electrical properties tomography studies are based on direct comparisons with ex vivo measurements carried out on post-mortem samples in the 90’s. As a result, the in vivo conductivity values obtained from MRI in the megahertz range in different types of tissues (brain, liver, tumors, muscles, etc.) found in the literature may not correspond to their ex vivo equivalent, which still serves as a reference for electromagnetic modelling. This study aims to pave the way for improving current databases since the definition of personalized electromagnetic models (e.g. for Specific Absorption Rate estimation) would benefit from better estimation. Seventeen healthy volunteers underwent MRI of both brain and thorax/abdomen using a three-dimensional ultrashort echo-time (UTE) sequence. We estimated conductivity (S/m) in several classes of macroscopic tissue using a customized reconstruction method from complex UTE images, and give general statistics for each of these regions (mean-median-standard deviation). These values are used to find possible correlations with biological parameters such as age, sex, body mass index and/or fat volume fraction, using linear regression analysis. In short, the collected in vivo values show significant deviations from the ex vivo values in conventional databases, and we show significant relationships with the latter parameters in certain organs for the first time, e.g. a decrease in brain conductivity with age.

Manufacturing trials of PFCs with low thermal conductivity features for limiters

In future demonstration fusion power plants, plasma facing components will face high steady state and ultra-high transient heat loads from the plasma. Introducing low thermal conductivity features to the component can reduce the peak temperatures seen by the coolant pipe during transient loads, but at the trade-off of a loss of steady-state performance. Producing low-conductivity tungsten by additive methods has been investigated elsewhere, so this trial investigates production through subtractive means i.e., conventional milling. This method preserves the original temperature limits and majority of the microstructure and is much higher Technology Readiness Level (TRL) so requires less development to reach series manufacture. In this trial, diamond drilling produced holes in monoblocks down to 0.6 mm and ligaments down to 0.7 mm, showing that this method is capable of producing small features in a controlled way. With the geometric design of lattice used in this trial, these samples achieved thermal conductivity reductions of 15% to 40%. One monoblock assembly was tested up to 1100 °C for 500 cycles in the Heating by Induction to Verify Extremes (HIVE) High Heat Flux test rig and showed no signs of ligament cracking or thermal degradation. Electromagnetic modelling has been validated against the experimental results, so future designs can be accurately modelled ahead of testing in HIVE.

Electromagnetic Optimization of a High-Speed Interior Permanent Magnet Motor Considering Rotor Stress

High-speed interior permanent magnet (IPM) motors require highly reliable rotors. Some measures must be adopted to improve rotor safety, but its electromagnetic performance is seriously affected. It is a challenge to achieve excellent electromagnetic characteristics while satisfying mechanical strength. This paper presents an electromagnetic optimization design of high-speed IPM motors considering rotor stress. Firstly, the permanent magnet (PM) is segmented by adding stiffeners to improve stress distribution. The effects of the bridge and stiffener thickness on the rotor stress and electromagnetic performance are analyzed. Secondly, an electromagnetic optimization model is built based on a three-segment PM rotor structure, aiming for maximum efficiency and minimum rotor core losses. Then, the initial design and optimized scheme are compared, the results show that the efficiency, safety and temperature performance of the motor are improved. Finally, a 140 kW, 18,000 rpm prototype is manufactured and tested. The above analysis provides a valuable reference for the design and widespread application of high-speed IPM motors.

Electromagnetic torque modeling and validation for a permanent magnet spherical motor based on XGBoost

As a device characterized by multiple degrees of freedom in one driving unit, analytical electromagnetic torque modeling is needed for the rotor position tracking control of a Permanent Magnet Spherical Motor (PMSpM). In this paper, Extreme Gradient Boosting (XGBoost) was proposed to be employed for establishing the output relationship between the rotor position and the electromagnetic torque of PMSpM. The Finite Element Method (FEM) was applied to obtain train data and test data concerning the rotor position and electromagnetic torque of PMSpM. Particle Swarm Optimization (PSO) was applied to optimize partial parameters of XGBoost, which serves to enhance the modeling accuracy of electromagnetic torque via XGBoost. The predictive results of algorithms, including Random Forest (RF), Gradient Boosting Regression Tree (GBRT), Multi-task Gaussian Process (MTGP), and XGBoost, were compared with FEM results and experimental results over multiple indicators. The capability of XGBoost has been validated not only to perform modeling tasks within an abbreviated time span but also to generate models that display amplified accuracy and efficiency.

Integrated high gain linear leaky wave antenna

Formulation of the problem. In the microwave range, the implementation of radar systems for spatial surveillance, remote sensing and information transmission systems requires relatively simple and reliable low-profile antennas that have a narrow radiation pattern in one of the planes and a high gain. Purpose. Demonstrate the feasibility and efficiency of implementing a high-gain linear antenna based on a periodic leaky wave antenna with series feeding of an integrated aperture. Results. The possibility of effective implementation of an antenna system with a high gain based on a linear periodic leaky wave antenna in the range of 9.2-9.5 GHz is shown. The radiating aperture of the antenna contains a flat dielectric waveguide integrated with a metal periodic grating with rectangular grooves. The values of the geometric parameters of the emitting aperture are indicated. The results of mathematical modeling using an original 2D computational algorithm and full-wave 3D electromagnetic modeling are presented, confirming the effectiveness of the antenna design with the stated geometric parameters. Practical significance. The developed integrated periodic leaky wave antenna of the microwave range can be used to increase the azimuth resolution and range of radar systems, increase the energy potential of information transmission systems without increasing the transmitter power.

Magnetic Resonance Imaging-Compatible Electromagnetic Actuator: Design and Tests

This paper presents the detailed design, construction and tests of a protype iron-free MRI-compatible electromagnetic actuator. The originality of this proposal lies in the use of the homogeneous static magnetic field B0, present in the MRI bore, to ensure the electromechanical energy conversion. The armature is composed of three rectangular coils in a three-phase arrangement, which makes the actuator very light-weight and compact. The operating principle is that of an AC synchronous motor with a rotating armature. In order to design the actuator, a 3D analytical electromagnetic model is developed to predict the magnetic field produced by the armature winding. Then, a 3D finite element (FE) computation is performed to validate the analytically calculated magnetic field. The developed analytical model is then inserted into an optimization routine based on Genetic Algorithms (GAs) to obtain the prototype dimensions to be realized. Finally, the prototype is constructed and tested inside an MRI research scanner. The results indicate that the reduction in the Signal-to-Noise Ratio (SNR) and the geometrical distortion are less than 5% when the actuator is powered with a current of 10 times the rated one and when it is located very close to the subject to be imaged.