Search Results (401)

Taking a typical high-power microwave power supply system as the research object, this paper quantitatively simulates and compares electromagnetic disturbance characteristics under multiple operating conditions, systematically investigates the influence mechanism of the system on EMI, and verifies the proposed simulation model via prototype experiments. Firstly, the typical equipment composition and three operating modes of the system are elaborated. Standardized high-frequency equivalent circuits of thyristors, capacitors, and inductors are established, and parasitic parameters are extracted to construct a system-level high-frequency coupling model. Different from traditional static parasitic extraction and separated field-circuit simulation methods, the proposed global collaborative optimization co-simulation method with voltage-dependent thyristor parasitic model significantly improves EMI prediction accuracy under full-cycle multi-mode operation. Secondly, based on the dynamic device characteristics under resonant charging, energy recovery and energy supplement modes, the generation mechanisms of EMI are clarified with quantitative data. During modeling, the electrical characteristics of thyristor body diodes and inter-electrode capacitances are fully incorporated with reference to actual component parameters. The EMC co-simulation based on CST field-circuit coupling is adopted to collaboratively optimize all parameters, which reduces the approximation error introduced by local modeling and greatly improves simulation accuracy. Combined with simulation and prototype experimental verification, this paper reveals the multi-path EMI coupling mechanism of pulsed power systems. The proposed parasitic parameter-based SPICE modeling and field-circuit co-simulation method can provide quantitative analysis tools and theoretical support for the EMC suppression design of high-power microwave power supplies. Full article

The article is aimed at studying the features of the hot rolling mill CWBRM-1700 of JSC “Qarmet”, which negatively affect the operation of the distribution network of the workshop. Such factors are frequent shock loads of technological mechanisms with high installed capacity of the equipment. Experimental studies of the distribution network of the rolling production on the buses of the 10 kV substation showed that shock loads of synchronous electric drives of roughing stands lead to periodic voltage drops of up to 13% lasting 5–6 s. Mathematical modeling in the MATLAB/Simscape/Electrical environment, the results of which coincide with the data of the experimental study, showed that the most significant factor affecting the quality of electricity are abrupt changes in the reactive power of the synchronous motor from −0.5 to +0.5 MVAR. To solve the problem, it is proposed to use a controlled filter-compensating device. Variants of circuit solutions for such devices are considered. The choice was made in favor of a three-phase adjustable LLC filter with diode–transistor keys. The article develops a method for calculating the electromagnetic parameters of such a filter and establishes that in order to reduce the level of harmonic distortion of voltage, it is necessary to use a triangle connection of the controlled reactive compensator and select the PWM frequency of the transistors, a multiple of the tripled frequency of the power grid. Two options for creating a closed-loop control system for energy modes are studied: a reactive power stabilization system and a voltage stabilization system in a distribution network node, which reduce the duration of transient processes to 0.5 s and reduce the voltage drop in the network node to −4 to + 1% in the first case and to −4 to + 3% in the second, also reducing reactive power consumption to 0.02 MVAR and 0.25 MVAR, respectively. The advantage of a closed-loop control system with voltage stabilization is the ability to use a technically less complex voltage sensor. Full article

Accurate extraction of single-diode model (SDM) parameters is essential for photovoltaic performance analysis, especially when only datasheet values or graphical I-V characteristics are available. This study presents a graphical–deterministic parameter extraction framework that combines calibrated curve digitization, local differential analysis, uncertainty-aware slope estimation, and analytical SDM closure. Unlike conventional datasheet-based analytical methods that operate directly from tabulated characteristic points, the proposed approach explicitly incorporates the graphical-to-numerical conversion stage and evaluates its impact on the estimation of the resistive parameters. The shunt and series resistances are obtained as effective local slope estimates near short-circuit and open-circuit conditions, respectively, while the photocurrent, saturation current, and ideality factor are determined from characteristic operating point equations. The ideality factor is solved through a deterministic scalar root procedure within the physically admissible interval $1\le \mathrm{n}\le 2$. The method was evaluated using four photovoltaic devices, including laboratory-scale cells and commercial modules. Normalized reconstruction errors of 0.82% and 0.88% were obtained for the RTC-France cell and the KC200GT module, respectively. The INAOE laboratory cell and the SP450M half-cut module showed higher sensitivity to graphical slope extraction and energetic closure. For the SP450M module, the use of an equivalent series cell number ${\mathrm{N}}_{\mathrm{S},\mathrm{e}\mathrm{q}}$ = 72 improved agreement with the digitized graphical I–V curve, although the reconstructed maximum power remained below the nominal datasheet value, revealing a graphical/datasheet consistency issue. These results show that the proposed framework is a transparent and reproducible alternative for SDM identification from graphical sources, while also defining its sensitivity limits when applied to low-resolution curves or half-cut high-power modules with complex equivalent electrical configurations. Full article

To establish quantitative criteria for selecting the operating frequency of diode rectifier unit (DRU)-based medium-frequency AC collection and DC transmission systems, this paper proposes a life-cycle frequency-selection method for far-offshore wind power. A power-flow model incorporating wind-turbine Q–f droop control and frequency-dependent submarine-cable parameters is developed to evaluate voltage distribution, reactive-power accumulation, power factor, and steady-state losses. An electromagnetic transient model is then used to quantify energy losses caused by single-phase and three-phase AC-side short-circuit faults. These electrical results are integrated with cable and converter investment costs in a multi-stage life-cycle economic model that accounts for equipment aging and loss growth. For the studied Rudong 500 MW case under the adopted baseline parameters, medium-frequency operation increases submarine-cable reactive-power accumulation and fault losses, while the total life-cycle cost first decreases and then increases with frequency. The minimum cost occurs at 180 Hz. The proposed framework links steady-state performance, transient fault losses, and long-term economics, providing a project-oriented basis for selecting the operating frequency of DRU-based offshore wind transmission systems. Full article

Efficient thermal management of high-power electronic components has become a critical engineering challenge as power densities grow and device geometries shrink. Conventional solutions based on passive heatsinks and mechanical fans are increasingly inadequate in applications where noise, reliability, and compactness are paramount. This paper presents a comprehensive Computational Fluid Dynamics (CFD) investigation of ionic wind—an Electro Hydro Dynamic (EHD) phenomenon in which a corona discharge between asymmetric electrodes generates a directed airflow without any moving part—as an energy-efficient alternative for cooling high-power electronics. A fully coupled 2D Multiphysics model is developed in COMSOL Multiphysics, integrating electrostatics, ion transport (Nernst–Planck), Navier–Stokes fluid dynamics, and convective heat transfer. The 2D formulation, while computationally efficient and consistent with prior EHD modeling studies, neglects lateral jet spreading inherent to a real three-dimensional needle configuration and is therefore expected to overestimate peak impingement velocities; quantitative comparisons with experimental temperatures are interpreted with this limitation in mind. The study focuses on a needle–collector configuration applied to a heated aluminum plate representative of a high-power electronic component such as a Light Emitting Diode (LED), a power transistor, or a microprocessor die. Simulation results are indirectly validated against experimental data obtained by Schlieren optics on a high-power (Chip-On-Board) COB LED system. The ionic wind reduces the maximum surface temperature by 8.1 K and substantially attenuates the central hotspot, redistributing heat laterally. A systematic parametric study reveals that applied voltage and needle height above the heat source are the dominant design parameters, while an energy balance shows that the EHD jet directly evacuates approximately 1.8% of the generated heat—acting primarily as a surface convection enhancer rather than a bulk heat extractor. These findings provide quantitative design guidelines applicable to any power electronic component cooled by an EHD system. Full article

Parallel DC/DC converter modules provide a feasible approach for achieving power scalability in various power conversion systems. This paper investigates an MOSFET-based lagging leg series diodes phase-shift full-bridge (LLSD-PSFB) converter and proposes a three-loop current-sharing control strategy for coordinated parallel operation. The strategy incorporates a voltage loop, a current loop, and a current-sharing loop to mitigate load current imbalance caused by MOSFET parameter mismatches and module inconsistencies. The operating principle and parameter design of the single-module LLSD-PSFB converter are analyzed, and an averaged model is established. Based on this model, a small-signal model of the parallel system is derived to evaluate system stability and current-sharing performance. Simulation results demonstrate that the proposed control scheme effectively improves current-sharing accuracy and dynamic response. An experimental prototype is developed to validate the theoretical and simulation results. The experimental results confirm that the proposed three-loop control strategy achieves high current-sharing precision and stable operation, demonstrating its effectiveness for parallel DC/DC converter systems and its potential for scalable high-power applications. Full article

To meet the conflicting demands of real-time simulation and high fidelity for thermal modeling of IGBT modules in digital twin applications, this paper presents a dynamic thermal network parameter updating strategy. A hybrid thermal model is constructed by combining a high-fidelity finite-element-method reference model with a 3-D compact network. Initial thermal resistance and capacitance parameters are obtained via offline calibration and validated against the transient thermal impedance curve. A dynamic identification method based on recursive least squares with precomputed sensitivity matrices is then proposed. It dynamically updates each independent thermal branch using only real-time chip junction temperature measurements. The Vincotech full-bridge IGBT module is used for simulation validation. The proposed method achieves steady-state identification errors of 3.2% for the IGBT chip thermal resistance and 4.5% for the freewheeling diode chip thermal resistance, outperforming particle swarm optimization and dual Kalman filter in both convergence speed and steady-state accuracy. Thus, it satisfies the requirements of real-time tracking and dynamic evolution for thermal models in digital twin systems. Full article

Metasurface absorbers play a critical role in microwave electromagnetic control, yet conventional designs suffer from fixed performance and strong cross-coupling between tunable parameters, limiting their adaptability in dynamic environments. Here, we propose a dual-band reconfigurable metasurface absorber with independent modulation of absorption intensity and frequency. The absorber adopts a double-layer metallic structure integrated with PIN diodes and varactors, realizing independent regulation of absorption intensity and frequency. In the lower band (4.1–7.7 GHz, S₁₁ < −10 dB), the absorption intensity is continuously tunable via the PIN diode bias without frequency shift, while in the upper band (13.4–14.4 GHz), the absorption frequency is continuously tunable via the varactor bias without intensity variation. Quantitative cross-sensitivity analysis yields a frequency shift of less than 1.5% during intensity tuning and an intensity variation of less than 0.8 dB during frequency tuning. The absorber exhibits polarization insensitivity and stable performance under oblique incidence up to 45°. An equivalent circuit model is developed and validated against full-wave simulations. Numerical analyses of fabrication tolerance for the active components confirm that the highly decoupled behavior is robust, with absorption peak shifts below 0.15 GHz and intensity variations below ±1.2 dB. Our conceptual design highlights the potential towards independent multi-parametric control in reconfigurable metasurface absorbers for adaptive electromagnetic shielding, smart radomes, and frequency-agile sensing. Full article

Autofluorescence of microorganisms has emerged as a potential tool in diagnostics. However, the temporal behaviour of fungal autofluorescence and its objective quantitative evaluation remain insufficiently characterised. The present in vitro study investigated the temporal dynamics of autofluorescence in 16 reference fungal strains under 405 nm laser excitation, with a particular focus on quantitative colour analysis. Standardised fungal suspensions were cultured on Sabouraud dextrose agar and imaged after 24–168 h of incubation. Fluorescence images were acquired during excitation with a 405 nm diode laser. The images were analysed in ImageJ using the HSV colour model, with the mean hue value of the colony used as the primary quantitative parameter. Multifactorial ANOVA demonstrated significant effects of fungal strain and strain × time interaction on hue values (p < 0.001), whereas time alone was not significant. Most strains exhibited a progressive decrease in mean hue during cultivation, although strain-specific temporal patterns were observed. Blastoschizomyces capitatus maintained a stable high mean hue throughout the observation, while Candida guilliermondii showed a marked increase after 168 h. These findings underline the strain- and time-dependent nature of fungal autofluorescence and the importance of standardised imaging conditions not only for its potential diagnostic application but also for its use as an experimental tool in studies of fungal metabolism or stress responses. Full article

This study introduces an innovative approach to enhance the lifetime of power converters linked in a back-to-back configuration for Type-4 wind turbines. The proposed method involves periodically changing both the connection points and functions of the machine-side converter (MSC) and grid-side converter (GSC) at ultra-low frequencies. This adjustment enables shared usage of power semiconductor switch lifetime, specifically of the IGBTs in power modules and their diodes, across the inverter and rectifier modes. In addition, the method incorporates simulation-based tests to assess aging effects on semiconductors as part of the evaluation process. To validate this proposed strategy, simulations were carried out using PSCAD for modeling the wind turbine and converter systems, alongside MATLAB for developing thermal models, calculating losses, and determining expected lifetimes. The impedance parameters employed in the thermal network were obtained through manufacturer-led experimental data; furthermore, the estimated junction temperatures align with the results obtained from the manufacturer’s tool. The findings illustrate that the proposed approach can significantly improve the lifetime of wind turbine converter systems, by values of 85% or more, even if the swapping operation is implemented during maintenance work. Full article

Photovoltaic (PV) module faults, such as hotspots, diode short circuits, occlusions, and shadows, degrade power generation efficiency and safety. Existing manual inspection and single-modality methods show limited robustness under complex conditions, especially with illumination variations and weak thermal responses, while most deep learning approaches fail to exploit the complementarity of visible and infrared modalities. To address this issue, a dual-modality visible–infrared fusion framework based on YOLO11 is proposed, integrating a multi-scale pyramid pooling and dilated convolution module (MSPPD), a gradient-aware fusion module (GAFusion), and a dynamic convolution and element-wise scaling detection head (Detect-DEhead). GAFusion enhances cross-modal structural consistency and reduces feature misalignment and information loss during fusion by introducing gradient-aware feature interaction. Shape-IoU loss is employed to improve localization accuracy. The proposed method improves mean average precision (mAP)@0.5 from 86.7% to 88.1%, while reducing parameters, computational cost, and model size from 4.3 M to 3.7 M, 11.42 GFLOPs to 9.37 GFLOPs, and 9.1 MB to 7.9 MB, respectively. With Shape-IoU, mAP@0.5 reaches 88.4%, and recall increases from 78.5% to 84.9%. Experiments on the FLIR Thermal dataset achieve gains of 2.2%, 1.6%, and 2.7% in precision, recall, and mAP@0.5. The method achieves an effective trade-off between accuracy and efficiency for intelligent PV module inspection. Full article

High-power laser diodes are extensively utilized in advanced optoelectronic systems. These devices typically operate under high-current injection conditions, under which intrinsic parasitic parameters become non-negligible and exert a substantial influence on their electro-optical response characteristics. Furthermore, when multiple single emitters are monolithically integrated into a linear array along the epitaxial-layer direction on a single substrate, additional parasitic elements are inevitably introduced. These parameters are critical for characterizing the output performance of high-power laser diodes. This paper presents the implementation of an equivalent circuit model for large-signal laser-diode operation within the Advanced Design System (ADS) computer-aided environment. The proposed model enables accurate simulation of the device’s operating-voltage waveform and optical-output-power response under both DC steady-state and pulsed-transient driving conditions, thereby achieving a coupled representation of electrical behavior and optical emission. Sensitivity analysis of various parasitic elements is performed to systematically evaluate their influence on output characteristics and device reliability. The results provide theoretical guidance for structural optimization and packaging design, offering new insights into future modeling and reliability assessment of high-power laser diodes. Full article

In scientific research, the optimization of organic light-emitting diodes (OLEDs) is generally achieved through a lengthy and expensive experimental process as new ideas and configurations are tested on real devices. Electro-optical simulation allows for the rapid evaluation of key performance parameters of device structures, thus reducing manufacturing time and costs. This paper presents an original contribution to the electro-optical modeling and optimization of multilayer OLED devices using the Non-dominated Sorting Genetic Algorithm II (NSGA-II). This optimization explicitly incorporates defect states within the ITO/NPB/Alq₃:C545T/Alq₃/LiF-Al structure. The simulated model is calibrated using experimental data by fitting the trap state distribution. The Pareto front resulting from the multi-objective optimization identifies a set of non-dominated configurations, including an optimal intermediate structure defined by an electron transport layer (ETL) thickness of approximately 42 nm and a hole transport layer (HTL) thickness of approximately 53 nm. This configuration leads to a limited reduction of 1.75–2% in current efficiency (${\eta }_c$) while offering a remarkable improvement of 23–30% in power efficiency (${\eta }_p$) compared to the extreme configurations of the optimal Pareto set. Thus, this solution represents an optimal Pareto trade-off between high current efficiency and improved power efficiency. This paper shows that combining defect modeling and thickness optimization provides a reliable framework for the electro-optical optimization of OLED devices. Future work will extend this approach to spectral and colorimetric analysis. Full article

Real-time tracking of high-speed targets in autonomous systems requires detection and decision-making pipelines that can operate within sub-millisecond time budgets. Single Photon Avalanche Diode (SPAD) sensors are well suited for this task, offering 10 kHz Time-of-Flight (ToF) measurements with picosecond timing precision. However, processing such high-frequency time-series data with conventional deep learning models introduces computational bottlenecks that are difficult to handle on resource-constrained embedded hardware. This paper presents an ultra-lightweight, dual-head architecture built on the MiniRocket transformation algorithm, where a single shared feature extractor simultaneously feeds two independent decision pathways: one for multi-class target classification and one for 3-parameter kinematic regression covering velocity, pitch, and yaw. As a single-pixel sensor, the device provides only 1D range information; lateral 3D spatial localization is outside the scope of this work. To the best of the authors’ knowledge, this is the first application of MiniRocket to continuous kinematic estimation from high-frequency sensor data. Since collecting labeled physical flight data at these speeds is largely infeasible, a physics-based ray-casting simulation was developed to generate a 55,440-sample dataset across four 3D CAD target models under varying speed (100–450 m/s), orientation, and noise conditions. The proposed architecture achieves 98.6% classification accuracy and a velocity Mean Absolute Error (MAE) of 0.26 m/s, with orientation estimation yielding a pitch MAE of 3.47° and a yaw MAE of 2.46°—values consistent across all five cross-validation folds, indicating that the orientation performance floor is governed by the sensor’s physical angular resolution rather than by model capacity. With approximately 27,000 trainable parameters, the system completes full dual-task inference in 0.56 ms on a 16-core CPU (1785 Frames Per Second-FPS), satisfying the 1 ms real-time constraint of a 10 kHz sensor without GPU acceleration. It should be noted that the single-pixel SPAD architecture provides only 1D range-along-beam information; full 3D spatial localization is physically not extractable from a single sensor and is not addressed in this study. Full article

Thermally activated delayed fluorescence (TADF) emitters doped in host–guest systems are widely utilized for organic light-emitting diodes (OLEDs), where key rate constants and the fluorescence quantum yield (Φ_F) are strongly influenced by the surrounding environment. However, the multifaceted interactions, i.e., dipole–dipole interaction and conformational restraint between the emitter and environment have been rarely investigated systematically, where excited state charge transfer (CT) and structural relaxation (SR) of emitters should be considered equally. In this study, four representative CT–TADF emitters were selected as model systems and studied in PS/PMMA:TADF:CA host–guest doped films with varied dielectric constants and matrix rigidity. Within D–A and D–A–D configurations, donor substitution from PXZ to DMAC varied CT characteristics, whereas TRZ-based D–A and DPS-based D–A–D emitters provided a relative difference in SR owing to their different rigidity. The total reorganization energy (λ_Total) was introduced as a quantitative measure of these multifaceted interactions and correlated with the rate constants. The results indicate that the dielectric dependence of the nonradiative decay rate (k_nr^S) for D–A–D molecules cannot be explained by the simplified energy gap law, where the vibronic effect plays the role of a game changer. This work provides a quantitative framework and highlights vibrational frequency as a key design parameter for optimizing Φ_F in host–guest doped OLED devices. Full article