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On-Line Analysis of Oil-Dissolved Gas in Power Transformers Using Fourier Transform Infrared Spectrometry
摘要： To address the problem of on-line dissolved gas analysis (DGA) of a power transformer, a Fourier transform infrared (FT-IR) spectrometer was used to develop an analysis instrument. Carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), ethane (C2H6), ethylene (C2H4) and acetylene (C2H2) were the analytes for the FT-IR spectrometer while propane (C3H8), propylene (C3H6), propyne (C3H4), n-butane (n-C4H10) and iso-butane (iso-C4H10) were the interferents, which might exist in the dissolved gas but are not currently used as analytes for detecting an internal fault. The instrument parameters and analysis approach are first introduced. Specifically, an absorption spectra reading approach by switching two cone-type gas cells into separate light-paths was presented for reducing the effects of gas in the gaps between gas cells and spectrometers, scanning the background spectrum without clearing the sample cell, and increasing the dynamics. Then, the instrument was tested with a standard gas mixture that was extracted from insulation oil in a power transformer. The testing results show that the detection limit of every analyte component is lower than 0.1 μL/L, and the detection limits of all analytes meet the detection requirements of oil-dissolved gas analysis, which means that the FT-IR spectrometer may be an ideal instrument due to its benefits, such as being maintenance-free and having a high stability.
关键词： power transformer,oil-dissolved gas,gas chromatograph,spectral analysis,Fourier transform infrared spectrometer
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Smart Grid and Clean Energy Technologies (ICSGCE) - Sg. Long, Cheras, Kajang, Malaysia (2018.5.29-2018.6.1)] 2018 International Conference on Smart Grid and Clean Energy Technologies (ICSGCE) - H2D4-Type Single Phase Transformer-Less Inverter with Reactive Power Control for Grid-tied PV System
摘要： Transformer-less inverter is popular for grid-tied photovoltaic (PV) system due to low cost, smaller size and higher efficiency. However, one of the technical challenges, which need to be handled carefully, is the issue of leakage current. Moreover, an inverter must be capable of controlling the reactive power to a certain extend to maintain the power factor (PF) close to unity. Therefore, many inverter topologies have been proposed. In this paper, a new four diodes and two IGBT switch based H2D4-type highly efficient transformer-less inverter is proposed that can handle the issue of leakage current maintaining low total harmonic distortion (THD) and higher PF where the common mode (CM) voltage is maintained constant. As a result, the leakage current deceases and the conduction loss as well as size of the system is decreased due to minimum number of IGBT switches. Furthermore, two control systems are proposed to control the reactive power with desire PF. The comparison among proposed H2D4 topology and conventional neutral point clamped (NPC) and H6 topology have been analyzed in this paper. To validate the accuracy of the theoretical analysis, the compared topologies are simulated in MATLAB/Simulink software. It is found that the PLL and PI closed loop control based H2D4 inverter topology controls the reactive power maintaining a low current THD with higher efficiency and high PF as compared to the system with only PI control based topology.
关键词： total harmonic distortion,leakage current,H2D4 topology,reactive power,transformer-less inverter,power factor,grid connected photovoltaic
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Self-powered Gate Driver Design for a Gallium Nitride Based Phase Shifted Full Bridge DC-DC Converter for Space Applications
摘要： Radiation hardened Gallium Nitride (GaN) Field Effect Transistors (FETs) for space DC-DC converter applications have been released to the market recently. However; space qualified digital isolators with small propagation delays, fast rise and fall times, and high common mode transient immunity necessary for isolated GaN gate drivers are not currently available. In this work, a self-powered isolated GaN gate drive circuit for a Phase Shifted Full Bridge DC-DC converter for space applications is designed and tested. Signal isolation and energy transfer to bias GaN gate driver chips are achieved using pulse transformers. Operation is successfully verified in a converter using 200 V radiation hardened GaN FETs and delivering 400 W from a 100 V DC bus. Experimental results show the effects that the voltage rate of change of the switch nodes have on dead time accuracy for the top switches in the proposed implementation, and a description of how better dead time accuracy was obtained is included.
关键词： rad-hard,radiation,hardened,phase-shifted,Gallium,self-powered,pulse transformer,space,gate driver,DC-DC,GaN
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Experimental Comparison of the Efficiency, Power Density and Thermal Performance of Two BIPV Converter Prototypes
摘要： This paper presents an experimental comparison between two series resonant full bridge converters for use in BIPV applications. The first converter employs Si MOSFETS and the second converter uses GaN HEMTs for the switches of the full bridge. The practical implementation and design of the boards and the trade-offs between components are highlighted. The efficiency, power density and thermal performance of the converters are discussed in detail. Practical issues, such as secondary oscillatory behaviour, in the development of a phase-shifted full bridge are highlighted. The used transformer is modeled, including all parasitic elements. Several solutions to avoid transient oscillations in the secondary are set forward. To mitigate these high-frequency voltage transient overshoots, the best solution was found to equip the primary of the converter with a series resonant tank.
关键词： transformer modeling,GaN,BIPV,resonant conversion
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 7th International Conference on Photonics (ICP) - Kuah (2018.4.9-2018.4.11)] 2018 IEEE 7th International Conference on Photonics (ICP) - Characterizing Inhibitor Content of Transformer Oil in the UV-Visible Waveband
摘要： Over the years, transformer oil has been used in majority of the power transformers to provide a reliable insulating system that is effective against dielectric stresses. Oxidation often occurred in transformer oil in the presence of oxygen and moisture which will affect the stability and insulating properties of the oil. The oxidation process cannot be eliminated but it can be delayed with the presence of inhibitor content. Even though inhibitor content can reduce the oxidation rate, the amount of inhibitor content still depletes over time. Thus, a monitoring system to detect the inhibitor content concentration is very crucial as it will be able to prolong the life span of the transformer. This paper focuses on the optical characterization of inhibitor content in transformer oil by utilizing the ultraviolet-visible (UV-Vis) spectroscopy technique. It was found that oil samples with inhibitor content produce multiple absorbance peaks in the range of 350 nm to 500 nm. A clear difference in peak absorbance near 450 nm indicates the difference in the inhibitor content concentrations. Based on the results of this work, a portable and low cost optical sensing device can potentially be developed for the detection of inhibitor content in transformer oil using UV-Vis spectroscopy.
关键词： Inhibitor,Visible spectroscopy,Power Transformers,Transformer Oil
更新于2025-09-04 15:30:14
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99 % Efficient 10 kV SiC-Based 7 kV/400 V DC-Transformer for Future Data Centers
摘要： The power supply chain of data centers from the medium voltage (MV) utility grid down to the chip level voltage consists of many series connected power conversion stages and accordingly shows a relatively low ef?ciency. Solid-State Transformers (SSTs) could improve the ef?ciency by substantially reducing the number of power conversion stages and/or directly interfacing the MV AC grid to a 400 V DC bus, from where tens of server racks with a power consumption of several kilowatts could be supplied by individual SSTs. The recent development of SiC MOSFETs with a blocking voltage of 10 kV enables the realization of a simple and hence highly reliable two-stage SST topology, consisting of an AC/DC PFC recti?er and a subsequent isolated DC/DC converter. In this context, an isolated 25 kW, 48 kHz, 7 kV to 400 V series resonant DC/DC converter based on 10 kV SiC MOSFETs is realized and tested in this paper. To achieve zero voltage switching (ZVS) of all MOSFETs, a special modulation scheme to actively control the amount of the switched magnetizing current on the MV and LV side is implemented. Furthermore, the design of all main components and especially the electrical insulation of the employed medium frequency (MF) transformer is discussed in detail. Calorimetric ef?ciency measurements show that a full-load ef?ciency of 99.0 % is achieved, while the power density reaches 3.8 kW/L (63 W/in3).
关键词： ZVS,isolated DC/DC,medium-voltage transformer,10kV SiC MOSFETs,soft-switching,Medium-voltage,calorimetric measurement
更新于2025-09-04 15:30:14