Wenying Yang

As a driving mechanism, the electromagnetic repulsion mechanism has been widely used in mechanical switches, such as circuit breakers, current limiters, and bypass switches, owing to its high closing speed and large output force. The dynamic characteristics and structural safety of electromagnetic repulsion mechanisms are critical to the stable and reliable operation of mechanical switches. However, the dynamic characteristics of electromagnetic repulsion mechanisms are affected by multiple factors, including coil parameters, energy storage parameters, armature structural dimensions, and air gaps. Moreover, strong coupling exists among these design variables. Parameter optimization that focuses solely on operating speed or electromagnetic force may lead to local stress concentration and edge vibration of the armature, thereby compromising the operational reliability of the mechanism. To address the difficulty in synergistically optimizing dynamic characteristics and structural safety, this paper proposes a two-stage optimization method that combines the series armature equivalent method, genetic algorithm-based multi-objective optimization, structural shape optimization, and topology optimization. In the first stage, a series armature equivalent model is established, and design parameters are optimized by the genetic algorithm to obtain a parameter combination that satisfies the requirements for displacement, closing speed, and operating time. In the second stage, under the constraints of dynamic performance, armature shape optimization, topology optimization, and combined shape–topology optimization are separately conducted to reduce edge vibration and local stress concentration of the armature. The dynamic characteristics, edge vibration displacement, and stress under different optimization schemes are comparatively analyzed. The results show that the proposed two-stage optimization method can effectively improve the structural response of the armature while ensuring that the dynamic characteristics of the mechanism satisfy the design requirements. In particular, after the combined optimization, the edge vibration of the armature is reduced to 41.8% of that before optimization, and the local stress concentration is significantly alleviated. The proposed optimization framework realizes the coordination between parameter design and armature structural optimization of electromagnetic repulsion mechanisms, providing a reference for improving the dynamic characteristics and structural reliability of electromagnetic repulsion mechanisms.

Hybrid relays can effectively reduce arc erosion on relay contacts, with the key technology lying in the commutation process between electromagnetic relays and power electronic switches. Accurate prediction of the commutation process remains challenging because the interaction between electromagnetic actuation, contact motion and arc behavior is often simplified or neglected. This paper proposes a sequential multiphysics modeling framework for the electromagnetic system drive and arc in a DC hybrid relay, building a multiphysics model of the hybrid relay during the commutation process. An electromagnetic finite element model is established to obtain the armature dynamics under actual driving conditions. The resulting contact displacement and velocity are then introduced as time-varying boundary conditions into a magnetohydrodynamic arc model to simulate the commutation process. The electromagnetic system model enables the calculation of contact arc dynamics under variable-speed conditions, thereby supporting the analysis of hybrid relay performance across different ambient temperatures. Furthermore, a dual-coil electromagnetic model of the relay is developed, and the coil power-up timing is optimized based on energy consumption. Simulation results demonstrate that the model effectively reflects the commutation process of the hybrid relay under electromagnetic drive. Moreover, experimental verification of the key components confirmed the model's accuracy. The work provides a universal theoretical tool for accelerating the design cycle of hybrid relays in the equipment manufacturing industry.

This study presents a piecewise analytical transient behavioral model for hybrid relays, aiming to describe the multistage current evolution during switching under combined resistive–inductive loads. By introducing a time‐sliced modeling framework based on the dominant conduction mechanism in each stage, the transient process is decomposed into semiconductor conduction, arc‐dominated conduction, and metal oxide varistor (MOV) energy absorption phases. Compared with conventional piecewise models mainly developed for single‐mechanism semiconductor devices, the proposed approach extends the analytical transient modeling methodology to hybrid switching devices involving multiple coupled physical mechanisms. An experimentally derived dynamic current model of MOV is incorporated to improve the prediction of transient characteristics during the commutation process. The influence of key parameters, including arc voltage and stray inductance, on current commutation characteristics is quantitatively evaluated through sensitivity analysis. The proposed model is validated by experimental tests and simulation calculations on hybrid relays in typical low‐voltage DC systems, demonstrating good agreement between measured and calculated results, as well as the effectiveness of arc suppression during switching.

The bypass switch is an important component for protecting the modular multilevel converter submodule in the flexible DC transmission system. Due to the low impedance of the flexible DC system, the fault current rises rapidly, imposing strict requirements on the closing speed of the bypass switch. As a linear actuator, the electromagnetic repulsion mechanism (ERM) can be a solution for the mechanical part of the bypass switch. At present, the ERM is primarily designed and optimized by the finite element method (FEM) and the equivalent circuit method (ECM). However, the FEM suffers from limitations such as low computational efficiency, large resource consumption, and model modification, while the inductance and inductance gradient required by the ECM are difficult to obtain. Moreover, the ECM divides the armature into multiple regions, resulting in highly ill-conditioned inductance matrix and inductance gradient matrix, which increases the risk of numerical errors. In this regard, a series armature equivalent method (SAEM) is proposed in this article to calculate the dynamic characteristics of ERM. First, the principle of SAEM is introduced, and the formulas of the electrical parameters are given. The calculation accuracy of the electrical parameters is verified by the FEM. Then, the dynamic characteristics of the ERM calculated by the ECM, the SAEM, and the FEM, are compared with the experimental results. The results indicate that SAEM has similar accuracy to the ECM, and it has more advantages in numerical stability. In addition, the SAEM has more advantages in calculation efficiency than the ECM and the FEM.

Liquid hydrogen is regarded as a key energy source and propellant for lunar bases due to its high energy density and abundance of polar water ice resources. However, its low boiling point and high latent heat of vaporization pose severe challenges for storage and management under the extreme lunar environment characterized by wide temperature variations, low pressure, and low gravity. This paper reviews the strategies for siting and deployment of liquid hydrogen storage systems on the Moon and the technical challenges posed by the lunar environment, with particular attention for thermal management technologies. Passive technologies include advanced insulation materials, thermal shielding, gas-cooled shielding layers, ortho-para hydrogen conversion, and passive venting, which optimize insulation performance and structural design to effectively reduce evaporation losses and maintain storage stability. Active technologies, such as cryogenic fluid mixing, thermodynamic venting, and refrigeration systems, dynamically regulate heat transfer and pressure variations within storage tanks, further enhancing storage efficiency and system reliability. In addition, this paper explores boil-off hydrogen recovery and reutilization strategies for liquid hydrogen, including hydrogen reliquefaction, mechanical, and non-mechanical compression. By recycling vaporized hydrogen, these strategies reduce resource waste and support the sustainable development of energy systems for lunar bases. In conclusion, this paper systematically evaluates passive and active thermal management technologies as well as vapor recovery strategies along with their technical adaptability, and then proposes feasible storage designs for the lunar environment. These efforts provide critical theoretical foundations and technical references for achieving safe and efficient storage of liquid hydrogen and energy self-sufficiency in lunar bases.