Most of the existing wireless power transfer system works in unidirectional with one-direction control signals. This paper presents a bidirectional wireless charging system with a duplex communication method, which is not only able to achieve the two-way wireless power transmission, but also transfers control signals bi-directionally. The power circuit operation mode is actively controlled by using the wireless transceiver module which can duplex communication to deliver measured signals remotely. The operational principle is analytically studied in details and is verified by simulation. Finally, a prototype of the bidirectional charging system using GaN devices has been successfully designed and tested. In addition, the measured feedback signals are effectively transmitted to validate the control algorithm.
The goal of the present paper is to investigate the aeration process and the enhanced effect of baffles in a full-scale commercial membrane bioreactor (MBR) system configured with a flat sheet (FS) membrane module. Through a computational fluid dynamics (CFD) simulation, two aerated FS membrane modules for full-scale applications with 26 membrane sheets were simulated. The numerical results indicate that the presence of baffles and the distances between the baffle and the outmost membrane sheet have a minor influence on the area-weighted shear stress for full-scale MBRs. In addition, bubble size and the bottom distance between the aerator and membrane bottom do not affect the average shear stress of full-scale FS membrane modules much. However, an increase in air flow rate has a significant effect on the area-weighted shear stress. A large FS membrane module is recommended, as it could achieve the same cleaning effect as the small one with a lower specific aeration demand for membranes.
Press pack Insulated Gate Bipolar Transistors (PP IGBT) are gaining more attention in HVDC power transmission systems due to their high-power density and high reliability compared with conventional power modules. Condition monitoring of PP IGBTs is normally conducted by estimating the chip temperature which is challenging to implement in practice. This paper presents a new parameter, deformation of the upper lid groove, to indicate the health condition of the PP IGBT based on its unique packaging technique. The thermal-mechanical coupled model is built by FE software in order to investigate the relationship between the deformation and junction temperature of the chips. In addition, the several feasible detection methods of deformation have been discussed and utilization of the fiber Bragg grating (FBG) sensor shows the advantages as the most appropriate approach, which can be further developed for condition monitoring using deformation measurements.
Press-pack Insulated Gate Bipolar Transistors (PP IGBT) are becoming increasingly used in HVDC and FACT applications. Due to its unique packaging, its reliability issues have also attracted increasing attention in the engineering field. More comprehensive investigation into the thermal, electrical and mechanical factors should be conducted to reveal the operation condition and status of the devices. The objective of this work is to study the relationship among the deformation of the collector groove and the thermal stress of the chip as well as the contact pressure by simulating the PP IGBT under normal and abnormal conditions. A sophisticated 3D finite element (FE) model of a PP IGBT has been developed which includes the coupling with thermal-mechanical effect. Also, the influence of different pressure and thermal stress on deformation is discussed thoroughly that can provide insight of how to monitor the status of a PP IGBT from the perspective of deformation.
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