Institute of Electrical Engineering

Equivalent contact resistivity is a key parameter that affects the dynamic process and overcurrent characteristic of the non-insulation (NI) HTS coil. Adding stainless-steel material between turns of a parallel-wound NI coil results in the formation of various types of internal contact interfaces. Therefore, describing the shunt behavior of the coil, i.e., the parallel-wound metal-insulation (PWMI) coil, requires more than one equivalent contact resistivity, which makes it difficult to determine their specific values only through coil inductance and time constant. To handle this problem, we propose a method for acquiring distinct equivalent contact resistivities of the PWMI coil. In this method, the equivalent contact resistivities are inverted based on the measured coil voltage or magnetic field. The bridge to connect the experimental data and equivalent contact resistivities is the streamlined field-circuit coupling model based on T-A formulation, which can reflect the complex electromagnetic topology and the distribution of equivalent contact resistivities of the PWMI coil. After obtaining the measurement results, the least squares method is used to optimize the equivalent contact resistivities until the simulation curve is sufficiently consistent with the experimental curve. In order to improve the efficiency of the optimization, we construct the lumped circuit model of the PWMI coil. Before the optimization process begins, the initial values of equivalent contact resistivities can be obtained based on this model, which can reduce the search scope of the optimization. The results of multi-process testing indicate that using the equivalent contact resistivities obtained by the proposed method can effectively predict the transient behavior of the coil.

Frataxin is a highly conserved mitochondrial protein that plays a key role in iron homeostasis and metabolism, and its deficiency leads to oxidative stress, mitochondrial dysfunction, and neurodegeneration. Hypomagnetic fields (HMF) can lead to various biological effects including increased oxidative stress, neurological and developmental disorders; yet, their effects acting as environmental stressors that exacerbate the inherent metabolic vulnerabilities in frataxin-deficient Drosophila melanogaster flies are still unknown. In this study, the bio-effects of HMF on growth, development, reproduction, and temperature stress resistance of frataxin-silenced flies were investigated. The results showed that HMF extended egg-to-adult and pupa developmental durations of both the control line of repo-GAL4; tub-GAL80^ts>GFP-RNAi (GFP-RNAi) and frataxin-deficient line of repo-GAL4; tub-GAL80^ts>fh RNAi (fh-RNAi) compared to those reared under a geomagnetic field (GMF). Compared with GMF, HMF significantly increased offspring fecundity in fh-RNAi flies, whereas the change in GFP-RNAi controls was not significant, while showing no significant effects on the adult weight of fh-RNAi flies. The impact of HMF on temperature stress resistance was particularly specific: it enhanced recovery from chill coma in control (GFP-RNAi) flies, while it accelerated recovery from heat shock in frataxin-silenced (fh-RNAi) flies. The mechanisms through which HMF modulate frataxin-associated phenotypes at a fundamental physical level warrant further investigation.

In the context of carbon neutrality, port power systems—often characterized by high energy consumption from large cranes—face the imperative to integrate renewable energy sources. However, fluctuations on both the source and load sides present major challenges to system stability. This study holistically addresses the system, which comprises “source,” “grid,” “load,” and “storage,” by focusing on the “load” and “storage” dimensions, with particular emphasis on the multi-dimensional characteristics of alkaline electrolyzers (AE). An innovative multi-time scale control strategy for the electric-hydrogen coupling system is proposed, integrating AE operational features to mitigate power imbalance. First, a multi-objective logistics scheduling method is introduced, simultaneously optimizing economy and power imbalance. Building on this, an hour-level optimal scheduling approach is developed for day-ahead optimization of equipment economy, followed by a 15-minute rolling scheduling method for intra-day refinement of battery state of charge (SOC) and control reliability. Finally, a 30-second real-time control strategy leverages fast-response devices to resolve power imbalances. Validated on the MATLAB-YALMIP platform, the proposed strategy improves economic performance by 33.8% and reduces power imbalance by 35.1% compared to conventional methods. The power imbalance under the control strategy with the objective of maximizing the local consumption of renewable energy is significantly alleviated, which confirms the effectiveness of the proposed method.

Accurate lightning data are critical for disaster warning and climate research. This study systematically compares the Fengyun-4A Lightning Mapping Imager (FY-4A LMI) satellite and the Advanced Time-of-arrival and Direction (ADTD) lightning location network in the Beijing-Tianjin-Hebei (BTH) region (April–August, 2020–2023) using coefficient of variation (CV) analysis, Welch’s independent samples t-test, Pearson correlation analysis, and inverse distance weighting (IDW) interpolation. Key results: (1) A significant systematic discrepancy exists between the two datasets, with an annual mean ratio of 0.0636 (t = −5.1758, p < 0.01); FY-4A LMI shows higher observational stability (CV = 5.46%), while ADTD excels in capturing intense lightning events (CV = 28.01%). (2) Both datasets exhibit a consistent unimodal monthly pattern peaking in July (moderately strong positive correlation, r = 0.7354, p < 0.01) but differ distinctly in diurnal distribution. (3) High-density lightning areas of both datasets concentrate south of the Yanshan Mountains and east of the Taihang Mountains, shaped by topography and water vapor transport. This study reveals the three-factor (climatic background, topographic forcing, technical characteristics) coupled regulatory mechanism of data discrepancies and highlights the complementarity of the two datasets, providing a solid scientific basis for satellite-ground data fusion and regional lightning disaster defense.

With the rapid development of electric vehicles and renewable energy technologies, research on wide voltage gain techniques for bidirectional converters has attracted significant attention. This paper addresses the technical bottleneck of limited voltage gain adjustment range in bidirectional CLLLC resonant converters, particularly the flat gain characteristics in the aboveresonance operating region, by proposing a resonant converter control strategy based on hybrid bridge-arm structure. The inverter-side switching network can operate in three configurations: half-bridge structure, full-bridge structure, and full-halfbridge structure. Through effective coordination of these three configurations, the step-down capability of the resonant converter can be significantly enhanced while maintaining fixed switching frequency. The proposed strategy requires no additional components and effectively avoids the issue of wide-range sudden changes in switching frequency during full-bridge/half-bridge transitions encountered in conventional solutions. Furthermore, multiple parameters are introduced to derive the voltage gain and loss distribution of the proposed control method, with analysis conducted on its extensibility to other bridge-arm configurations. Finally, the feasibility of the proposed control method is experimentally verified using a 10kW prototype