Q. Jane Wang

Paralleling SiC MOSFETs is an effective way to increase current and power rating. Current sharing in parallel operation is an important goal for improving system stability and reliability. However, parasitic parameters and other factors can cause current imbalance when SIC MOSFETs are connected in parallel. If there is severe current imbalance among the paralleled SiC MOSFETs, it may reduce their lifespan or even cause damage, thereby compromising system safety and reliability. This paper proposes an active feedback loop to control the gate current of SiC MOSFETs to achieve dynamic current sharing. The effectiveness of this method is verified through simulation.

This paper focuses on the dynamic current sharing problem of multi-tube parallel SiC MOSFET in high-power applications, analyzes the key influencing factors, and conducts a comparative analysis of the two current sharing methods. In megawatt-level power systems, the demand for multi-tube parallel topologies has soared, but the problem of current dynamic imbalance is prominent. Although SiC MOSFETs suppress static uneven current through the positive temperature coefficient of onresistance, dynamic current sharing remains a technical difficulty. The discreteness of parameters such as threshold voltage, transconductance, parasitic inductance at the source, and driving resistance significantly aggravates the dynamic current imbalance. After that, we analyzed and compared the two current sharing methods. Among them, the active gate drive technology controls the current sharing in real time by actively adjusting the gate signal. The drain-coupled inductor technology, on the other hand, forces current balancing through magnetic coupling. Finally, it was verified through simulation that both can effectively improve the current-sharing performance. Finally, the advantages and disadvantages of both were compared and analyzed through simulation, so that we can adopt a more appropriate method in future engineering practice.

Stator wound field flux switching (SWFFS) motors are gradually applied to electric vehicles, rail transit and other fields due to their armature windings and excitation windings are concentrated on the stator, so its stator and rotor structure is simple, and has the advantages of low production cost, wide speed regulation range, low vibration and noise, etc., and has broad development prospects. Due to the common problem of low torque density of rare earth motors, this paper analyzes the structure and operating principle of 24/14-pole SWEFS motor based on the background of vehicle-mounted low-voltage DC auxiliary power generation system, and uses the non-parallel stator cogging structure to improve the torque density of the motor, and significantly reduces the output torque ripple of the motor by adding the rotor pole shoe, and the feasibility of the structure is proved by finite element analysis.

Focusing on the low-speed operation control strategy of a permanent magnet synchronous motor based on the model method, this paper investigates a position sensor-free algorithm for a permanent magnet synchronous motor based on a nonlinear magnetic chain observer, gives a limit-loop oscillator Fixed-frequency (FLCO), and combines the FLCO-FLL algorithm to give the corresponding control rate and transfer function, and builds a model for simulation on the platforms of MATLAB/SIMULINK platform to build a model for simulation, and the proposed algorithm is analyzed and the suppression of interference by the algorithm is verified.

As one of the core components of electric vertical takeoff and landing vehicles, the motor driver is required to have strong anti-interference ability, small size, and high efficiency. This paper uses Silicon carbide (SiC) MOSFETs as power devices for the main drive inverter section of motor drivers. However, due to the high switching frequencies and low threshold voltage of SiC MOSFETs, parasitic parameters have a significant impact on their switching characteristics at high operating voltage levels. Bridge arm crosstalk and electromagnetic interference are particularly prominent issues. Based on this, this paper studies the anti-interference performance of SiC power devices and proposes relative solutions for practical applications. Finally, this paper completes the design of a control board based on DSP and a driver board based on SiC MOSFET. And the feasibility of the designed high immunity SiC MOSFET motor driver was experimentally verified.

BACKGROUND: The objective of this study was to comprehensively review the literature on Shear Wave Elastography (SWE), a non-invasive imaging technique prevalent in medical ultrasound. SWE is instrumental in assessing superficial glandular tissues, abdominal organs, tendons, joints, carotid vessels, and peripheral nerve tissues, among others. By employing bibliometric analysis, we aimed to encapsulate the scholarly contributions over the past two decades, identifying key research areas and tracing the evolutionary trajectory of SWE. METHODS: For this study, we selected research articles related to SWE published between 2004 and March 2024 from the Web of Science Core Collection (WOSCC). We utilized sophisticated bibliometric tools, such as CiteSpace, VOSviewer, and SCImago Graphica, to analyze the trends in annual publications, contributing countries and institutions, journals, authors, co-cited authors, co-cited references, and keywords. RESULTS: Our analysis yielded a total of 3606 papers. China emerged as the leading country in terms of publication output, with a strong collaborative relationship with the United States. Sun Yat-Sen University was identified as the institution with the highest number of publications. The keyword “transient elastography” was the most prevalent, with “acoustic radiation force” being a focal point in the initial stages of SWE research. Recently, Contrast-enhanced Ultrasound (CEUS) has emerged as a new research focus, signaling a potential direction for future research and development. CONCLUSION: The global research landscape for SWE is projected to expand continuously. Future research is likely to concentrate on the integrated application of SWE and CEUS for diagnostic purposes, along with exploring the clinical utility of multimodal ultrasound that synergistically combines SWE with other ultrasound technologies. This bibliometric research offers a comprehensive overview of the SWE literature, guiding researchers in their pursuit of further exploration and discovery.

Electric and magnetic fields have been used in various ways to enhance the performance of lubrication systems. The presence of these fields can significantly change the properties of lubricants. The rapid adoption of electric vehicles (EVs) has presented new lubrication-related challenges due to the presence of electric current. There is an urgent need for an in-depth study of lubrication systems subjected to such fields. This paper highlights recent research works on several key areas of lubrication involving electric or magnetic fields, which are:1) electric double layer in lubrication, 2) electrorheological fluids, 3) magnetorheological fluids, 4) ferrofluids, and 5) typical fluids used in the current EVs and typical surface failures of bearing components in EVs. Commonly used lubricants in each area are reviewed; lubrication mechanisms and related mathematical models are summarized; methods for and results from numerical analyses and experimental explorations are discussed; and common features of lubrications in different fields are explored. Based on the current research progress in these fields and the classic generalized Reynolds equation, a generalized mechanical-electro-magnetic-thermal-field (MEMT-field) Reynolds equation is proposed to describe the aforementioned lubrication scenarios and the effects of coupled mechanical, electric, magnetic, and thermal fields, which can be solved with a numerical iteration method.