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Yongjian Li - IEEE Xplore Author Profile

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Capacitance is a key electrical parameter of capacitors in power electronic converters, and its estimation is important for the stable operation of the converters. This article presents a small printed circuit board (PCB) with Rogowski coils for measuring ripple voltage rate (dv/dt) and ripple current in an online and contactless manner to estimate the capacitance. Electric field coupling is utili...Show More
The iron cores of electrical equipment, which is laminated with electrical steel sheets, typically operate within specific temperature and stress ranges. However, conventional measurement methods often fail to account for the impact of these factors on magnetic properties. This article proposes a vector magnetic properties measurement system for electrical steel sheet featuring simultaneous loadin...Show More
The fixed-point iteration method is widely used in electromagnetic field analysis involving hysteresis property due to its strong robustness, but it has the problem of low computational efficiency. In this article, a modified fixed-point iteration algorithm is proposed where the convergence factor is adaptively adjusted for different time steps according to the variation of residuals, instead of b...Show More
Nanocrystalline pads are normally considered to be infeasible in inductive power tansfer (IPT) systems due to their excessive loss—thermal behavior. This article proposes a novel frequency-dependent optimization method, for core loss reduction and thermal mitigation within nanocrystalline pads designed for high-power density IPT systems. To explore the applicability of nanocrystalline in an IPT sy...Show More
Double-sided linear motors often encounter significant detent forces. To address this issue, a double-sided asymmetric primary staggered tooth permanent magnet linear synchronous motor (DSAPST-PMLSM) is proposed to suppress detent forces. This structure maintains equal lengths of the upper and lower primaries while having different tooth widths at the ends, forming staggered teeth. However, the st...Show More
An improved Preisach-type vector hysteresis model of inversed fashion considering magnetic anisotropy for nonoriented (NO) steel sheet is proposed in this paper. By introducing new mathematical expression and identification method for the anisotropy vector Everett function, tedious measurement of scalar magnetic properties along different cutting directions is circumvented and high order truncated...Show More
A model for predicting the vector hysteresis properties of non-oriented steel sheets under multiaxial stress is proposed. Based on the magneto-elastic energy of a single crystal and coordinate transformation from crystal to sample, the effective field contains anisotropy, and magneto-mechanical characteristics are derived. By combining the effective field with the energy-based (EB) model, the sens...Show More
This article presents a hysteresis model that incorporates the microstructural features of soft magnetic composites (SMCs). The anhysteresis curve is derived based on Globus’s model, which characterizes the continuous displacement of the domain wall within the particles. A static hysteresis model is then formulated by incorporating the particle size-related pinning field in the energy-based (EB) m...Show More
High-temperature superconductor (HTS) cables have great potential in power transmission. This study presents a comprehensive environmental and economic analysis of high-current stacked HTS cables. The analysis considers the impact of gap variation on both the environmental footprint and economic viability of the HTS cables. By optimizing the gaps between the HTS tapes, the cable losses and carbon ...Show More
As a crucial electromagnetic energy conversion component in solid-state transformers, high-power, and high-frequency transformers (HFTs) are regarded. Winding loss, deemed a significant constituent of the overall losses in high-power HFT, necessitates rapid and accurate computation for the optimization of transformer design and the tracing of hot spots. To mitigate winding loss induced by eddy cur...Show More
This paper introduces a physically-based anisotropic hysteresis model considering the microstructural features of non-oriented silicon steel. Drawing on the foundations of the Globus' model, the anisotropic anhysteretic curve is first deduced from the movement of the domain wall within individual grains. A static anisotropic hysteresis model is then proposed by considering the grain size related p...Show More
A model for predicting the vector hysteresis properties of non-oriented steel sheets under multiaxial stress is proposed. In this model, the sensibility of mechanical stress is accounted for both in the reversible and irreversible magnetization based on the magneto-elastic energy of single crystal and domain motion theory. Comparisons between measured and calculated curves and losses are performed...Show More
A modified fixed-point iteration algorithm is proposed for electromagnetic finite element analysis with a hysteretic material model. In this method, the convergence factor is dynamically adjusted at each time step based on the specific situation. It has been verified that this approach improves computational speed and stability in solving nonlinear hysteresis electromagnetic simulation problems.Show More
Hysteresis, as most important and intrinsic property of magnetic materials, however, is usually neglected in numerical analysis of electrical equipment due to its complicated history-dependent multi-valued nonlinearity, which will lead to inaccurate predictions of magnetic fields distribution and core loss. In this paper, an efficient implementation method of incorporating hysteretic material mode...Show More
With the widespread use of high-power high-frequency transformers in flexible dc transmission, high-power density motor drive control, and high-power charging fields, the vibration and noise of high-frequency transformers have been drawing more and more attention from the industry. The nanocrystalline materials are commonly used in the core structure of high-frequency transformers. Although it is ...Show More
As a key component of the solid-state transformer, high-frequency transformer (HFT) design is important to increase the efficiency and power density of the system. In order to enhance the thermal performance of HFTs, a novel matrix core structure is proposed without increasing volume. Modified calculation models are proposed for predicting electromagnetism and thermal characteristics more precisel...Show More
This paper aims to estimate the electromagnetic field distribution in a simplified transformer through two-dimensional (2-D) finite element analysis. Traditional neural networks typically take RGB or grayscale imageas inputs, which may not be optimal for dense regression tasks encountered in physics field estimations. To address this, we propose a novel approach that constructs datasets incorporat...Show More
Magnetic properties of electrical materials are of great significance to be accurately modeled and effectively incorporated in numerical analysis of electromagnetic fields. In this article, a hybrid technique (HYS) for solving nonlinear magnetic problems is proposed, combining the advantages of the traditional fixed-point (FP) technique and Newton-Raphson method (NRM). Besides, various material mo...Show More
Ultra-thin silicon steel is widely used as core material for high-performance electrical equipment. Accurately measuring and evaluating its magnetic properties are significant for the optimal design. This study investigates the measurement errors inherent in the traditional H-coils and B-probes for estimating magnetic properties. It introduces an improved B–H combined sensor, outlining the calibra...Show More
Fe-based soft magnetic material such as amorphous or nanocrystalline alloy is an alternative to the ferrite for magnetic cores of the medium-frequency transformers (MFTs) due to its high permeability and magnetic saturation. However, accurate core loss modeling is one of the major obstacles to design a high-power-density MFT, especially when considering the nonlinearity hysteresis B-H loop. Beside...Show More
In this article, we present AlGaN/GaN-based lateral Schottky barrier diodes (SBDs) on sapphire substrate with fully recessed anodes and $\text{a}\vphantom {_{\int }}$ high-permittivity field plate (FP). A specific ON-resistance of 3.2 $\text{m}\Omega \cdot $ cm2, an on/off current ratio of $10^{{10}}$ , and a reverse breakdown voltage (BV) of 2.5 kV are simultaneously achieved for the device w...Show More
Large-scale high temperature superconducting (HTS) magnets usually have tens of double/single pancake coil units. The structural optimization and manufacture of the magnet assembly result in varying axial gaps between adjacent pancakes. This brings additional difficulties for inserting the superconducting joints and dealing with the welding factors such as the gap, welding angle and overlapped len...Show More
This article investigates the influence of the winding configurations on the core flux density harmonics of the axial modular flux switching permanent magnet (AM-FSPM) and conventional flux switching permanent magnet (FSPM) machine. The relationships between air-gap flux density harmonics and stator–rotor core flux density harmonics of the AM-FSPM machine with toroidal winding (TW) and the FSPM ma...Show More
This article proposes a fault diagnosis method for power transistors of full-bridge power converter (FBPC) in switched reluctance motors (SRMs) based on a modified current detection strategy. First, the circuit status is analyzed for fault operation. A novel current measurement scheme based on cross-bridge current is then provided to obtain the enough current information, and two current variables...Show More
In high-frequency transformers (HFTs), Litz wire is widely adopted to reduce eddy current loss and improve efficiency. Despite the advantages that Litz wire brings, calculating the leakage inductance is also more difficult. As one of the key parameters of HFT, leakage inductance directly affects the power transmission performance. This article proposes a new model to estimate the leakage inductanc...Show More