A subproblem technique is applied to dual thin shell finite element formulations. Both the magnetic vector potential and magnetic field formulations are considered. The subproblem approach developed herein couples three problems: a simplified model with only inductors, a thin region problem using approximate interface conditions and a correction problem to improve the accuracy of the thin shell approximation, in particular near their edges and corners. Each problem has its own geometry and is solved on its associated finite element mesh.

A subproblem finite-element method is developed for correcting the inaccuracies near edges and corners inherent to thin shell models, for both magnetostatic and magnetodynamic problems. A thin shell solution, supported by a simplified mesh near the thin structures, serves as a source of a correction problem with the actual volumic thin regions alone in a homogeneous medium, concentrating the meshing effort on the thin regions only. Improvements of local fields are efficiently achieved and allow accurate force and loss calculations.

The shielding of buried three-phase high-voltage power lines can be done by placing them in conducting ferromagnetic U-shaped gutters covered with plates. In case of a perfect electrical contact between adjacent gutters and between adjacent cover plates, induced currents in the shield efficiently reduce the magnetic field generated by the cables. As however a perfect contact cannot be guaranteed, in practice, it is useful to quantify the effect of a defective electrical contact on the field reduction. From two-dimensional/three-dimensional finite element computations and experiments, the influence of the contact resistance on the shielding efficiency is investigated, as a function of the ratio of axial length to height of the shield elements. Furthermore, the effect of other parameters on the shielding efficiency is studied: the ratio of axial length to height, a parasitic air gap between the gutter and the cover plate and the type of the shield material. It was found that a low contact resistance deteriorates much more the shielding in case of an aluminium shield than in case of a steel shield. As expected, the effect is larger for shield elements with relatively short axial length with regard to the other dimensions. Nevertheless, the effect remains quite significant for aluminium shields with practically convenient dimensions.

This paper presents modeling and experimental studies on water spray coolers for commercial photovoltaic modules. This paper has compared the energy yield of four photovoltaic commercial modules that were installed with a fixed tilt angle being equal to the local latitude in central Vietnam, including one photovoltaic module using a water spray cooler and three photovoltaic modules without cooling. Experimental results on sunny days have been shown that the energy yield difference between four PV modules under the same working condition is lower than 1%. In addition, on sunny days when the set working temperature of the water spray cooler is 45 °C, the average improvement efficiency of a photovoltaic module using a water spray cooler compared to three reference photovoltaic modules is 2.64%, 3.83%, and 6.18%, for an average of 4.22%. A simple thermal–electrical model of a photovoltaic module with a water spray cooler has been developed and tested. The normalized root mean square error between simulated and measured results of photovoltaic module power output on a sunny day without cooling and with water spray cooler reached 6.5% and 8.5%, respectively. The obtained results are also demonstrated that the reasonableness of the simple thermal–electrical model of the photovoltaic module with water spray cooler and the feasibility of a cooling system is improved to increase the efficiency of the photovoltaic module. In addition, they can be considered as a basis for new experimental models in the future.

This paper proposed a novel 4-Level T-Type Reconfigurable Fault-tolerant Converter (4L-TRFC) to match the segmented winding structure and high torque performance of Axial Flux Modular-Stator Hybrid-Excitation Switched Reluctance Motor (AFMHSRM). The 7 operating voltage levels and 17 operating modes generated by the proposed converter can improve the converter’s fault tolerance while increasing the motor’s base speed and power. Firstly, the topology and operating principle are introduced, and the corresponding control strategy with fault protection and fault-tolerance method is proposed. Then, the effects of the control parameters on the torque of the driven motor and the performance during fault and fault tolerance are analyzed in detail through simulation, and the proposed converter is compared with other converters. Finally, the proposed converter-based AFMHSRM drive system is built for experimental testing, and the simulation and experimental results verify the proposed power converter’s effectiveness and high fault tolerance.

In pursuit of the objective of achieving "net zero emissions," many countries worldwide, including Viet Nam, have prioritized the utilization of photovoltaic technology for energy conversion. Specifically, the implementation of roof-top grid-connected photovoltaic systems (GCPV) has emerged as a highly efficient solution in urban areas. These systems offer several advantages, such as minimizing land usage, lowering monthly electricity expenses, preventing building heat, generating income for households, and reducing transmission and distribution costs. This article focuses on a comprehensive long-term analysis conducted on 51 roof-top GCPV systems in the tropical monsoon climate of Hue City, Viet Nam, during the period from 2019 to 2023. The analysis findings reveal that roof-top GCPV systems with a capacity of 3-6 kW are well-suited for households in the central region of Viet Nam, characterized by a tropical monsoon climate. These systems exhibit an average sizing ratio of 1.03. The annual average daily final yield peaked at 3.28 kWh/kWp/day in 2021 and reached its lowest point at 2.97 kWh/kWp/day in 2022. Notably, the typical slope of the yield gradually increases with the installed capacity and the studied year. Furthermore, the monthly average daily final yield demonstrates a seasonal pattern, with higher yields observed from March to August and lower yields from September to January, aligning with the climate of the study area. As the years progress, the capacity factor and performance ratio of roof-top GCPV systems display a declining trend. Throughout the entire study period, these systems successfully mitigated 664 metric tons of CO2 emissions. The evaluation of long-term yield data offers valuable insights for photovoltaic installers, operators, and system owners, aiding in system maintenance and optimizing load utilization across different time periods. Long-term performance can be used by energy managers and owners of roof-top GCPV systems to identify supply shortfalls and initiate countermeasures.