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[IEEE 2019 IEEE Energy Conversion Congress and Exposition (ECCE) - Baltimore, MD, USA (2019.9.29-2019.10.3)] 2019 IEEE Energy Conversion Congress and Exposition (ECCE) - Implementation of Flexible Large Power Transformers Using Modular Solid State Transformer Topologies Enabled by SiC Devices
摘要： Large power transformers (LPTs) have been a major concern of the electric power sector as a failure of a single unit can lead to temporary service interruption and utility damages. Replacement of such large and heavy transformer units is a challenging job as LPTs are custom-designed and hence entail long lead times due to its intricate manufacturing process and transportation. On the other hand, solid-state-transformer (SST) technology has evolved as an alternate option for the conventional line-frequency transformers, which offers comparatively reduced size and weight with the enhanced power quality features. With the advancement in wide-bandgap devices such as silicon carbide (SiC) and advanced power electronic converters, SSTs are able to deploy in medium voltage applications. Consequently, the utilization of SiC-SSTs for large power applications can mitigate some of the existing concerns of LPTs. In this paper, challenges and concerns associated with the existing LPTs are discussed. Possible SST modules/cells enabled by SiC devices, which can be connected in a modular structure to achieve multi-cell flexible large power SSTs (FLP-SST) are presented. The effectiveness of the discussed SST cells is validated using appropriate simulations and experimental results of the scaled SST prototypes.
关键词： solid-state transformers (SSTs),modular converters,Large power transformers,SiC Devices
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Optical Cavity-Less 40-GHz Picosecond Pulse Generator in the Visible Wavelength Range
摘要： A method combined ensemble empirical mode decomposition, Volterra model and decision acyclic graph support vector machine was proposed to improve adaptability, feature resolution, and identification accuracy when diagnosing mechanical faults in an on-load tap changer of a transformer. In detail, the ensemble empirical mode decomposition algorithm was applied to decompose the multi-channel vibration signals in the switchover process of the on-load tap changer. Then, a Volterra model for the mechanical state of the on-load tap changer was established based on time-frequency characteristics obtained through the use of the ensemble empirical mode decomposition algorithm. Moreover, a matrix of coefficient vectors was also used in the Volterra model. This method will not only reduce the aliasing effect of empirical mode decomposition but also obtain high-resolution characteristics of nonstationary vibration signals. Furthermore, taking the singular values of the Volterra coefficient matrix as the fault characteristic, the data states of the model for diagnosing the on-load tap changer were automatically classified and identified by establishing a rapid, multi-classification decision acyclic graph support vector machine model with a low misjudgment rate. Finally, based on a certain on-load tap changer, the test platform for simulating mechanical faults was built. On this basis, by using the proposed method, the vibration signals generated due to typical mechanical faults, such as loosening of moving contacts, lessening of transition contact, and motor jam were acquired and analyzed, thus validating the effectiveness of the method through case studies. Compared with other methods, the new method could overcome many defects in existing methods and it has higher fault identification accuracy.
关键词： signal processing algorithms,Mechanical variables measurement,power transformers,fault diagnosis,electromechanical devices,time series analysis,support vector machines,switches
更新于2025-09-11 14:15:04
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris, France (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - An Improved Mobile Calibration Standard for Transformer Loss Measurement Systems
摘要： Existing mobile calibration standard used for on-site calibration of transformer loss measurement systems has been upgraded. Master-slave configuration of programmable power sources is replaced with the external triggering and synchronization method which ensures the system stability below 50 ppm. Resolution in phase-settings between voltage and current generation is now improved about 2-digits down to 1 m°. And, measurement results are automatically evaluated with the corrected calibration values of system components.
关键词： on-site calibration,loss measurements,Distribution and power transformers,uncertainty,low-power factor
更新于2025-09-10 09:29:36
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High sensitivity detection of partial discharge acoustic emission within power transformer by sagnac fiber optic sensor
摘要： Partial discharge acoustic detection is an important monitoring tool for power transformer diagnosis, which was traditionally performed by mounting the piezoelectric transducers on the oil tank surface. The disadvantage of partial discharge acoustic detection is its low sensitivity when partial discharge occurs inside the winding, which greatly compromises the value of partial discharge acoustic detection. Fiber optic sensors that can be deployed within power transformer are expected to be a potential solution. In this research, we used a Sagnac fiber sensor system built in lab to investigate the benefits of using fiber optic sensor for partial discharge acoustic detection. Acoustic pulses were induced in oil outside the winding and in oil duct inside the winding of a single phase 50 kV transformer. Although both fiber optic sensor and piezoelectric sensor can effectively detect the acoustic pulses outside the winding, fiber optic sensor gained a much better sensitivity over piezoelectric transducer to detect the acoustic pulses originated inside the winding. We envisage that the proposed fiber sensor can be deployed in power transformers to significantly enhance the detection performance of acoustic emission induced by partial discharge.
关键词： acoustic transducers,power transformers,partial discharges,optical fiber transducers
更新于2025-09-09 09:28:46
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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