- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[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) - A Sampling-Based Ratio Bridge for Calibrating Voltage Transformers
摘要： This paper describes the setup of a sampling-based ratio bridge for calibrating voltage transformers. The advantage of this ratio method is that voltage transformers with different transformer ratios can be easily compared. Initial measurements of the components of the bridge indicate low systematic errors, negligible voltage dependency and low phase errors around 50 / 60 Hz. This indicates an attainable uncertainty of below 2 ppm for the ratio error and 0.5 μrad for the phase displacement of voltage transformers.
关键词： Voltage transformer,sampling,high voltage,uncertainty,precision measurements
更新于2025-09-10 09:29:36
-
Pd-doped MoS2 monolayer: A promising candidate for DGA in transformer oil based on DFT method
摘要： Density functional theory (DFT) method was carried out to simulate the adsorption of three dissolved gases on Pd-doped MOS2 (Pd-MoS2) monolayer. We initially studied the possible structures of Pd-MoS2 monolayer and found that the Pd dopant preferred to be adsorbed onto the surface by TMo site. The adsorption and desorption performance, along with the sensing principle of Pd-MoS2 towards three typical gases, including H2, CH4 and C2H2, were analyzed. These analysis indicated that Pd-MoS2 could be a satis?ed material for C2H2 and H2 sensing at speci?c condition; while it is unsuitable for detection of CH4 due to the weak interaction and extremely short recovery time. All these give a ?rst insight into the application of Pd-MoS2 for DGA, evaluating the working operation of the transformer through sensitive detection of H2 and C2H2. We are hopeful that this work would support informative knowledge for experimentalists to realize the potential of Pd-MoS2 in the ?eld of electrical engineering in the near future.
关键词： DGA,Transformer oil,DFT,Pd-MoS2 monolayer
更新于2025-09-10 09:29:36
-
[IEEE 2018 International Conference on Smart Electric Drives and Power System (ICSEDPS) - Maharashtra State, India (2018.6.12-2018.6.13)] 2018 International Conference on Smart Electric Drives and Power System (ICSEDPS) - A Preliminary Study on Harmonics Generated by the Grid-Connected PV System on Distribution
摘要： Increased generation of Power by Solar Photovoltaic (PV) system is seen as an alternative to fulfill the increased demand of electricity. And hence the increased usage of electrical load devices causes the non-sinusoidal waveforms of current and voltage into the distribution system which is the major reason for increasing operating temperature of transformer, leading to deterioration of the insulation and potential reduction in its life time. Hence this paper sheds some light on the effects of THDi and THDv (Total Harmonics Distortion) and how it affects the life of any distribution transformer. The study is implemented by using MATLAB/Simulink version R2015b software.
关键词： temperature rise,nonlinear load,Distribution transformer,life expectancy,Harmonic distortion
更新于2025-09-10 09:29:36
-
[IEEE 2018 International Power Electronics Conference (IPEC-Niigata 2018 –ECCE Asia) - Niigata, Japan (2018.5.20-2018.5.24)] 2018 International Power Electronics Conference (IPEC-Niigata 2018 -ECCE Asia) - A Novel Single- Stage High-Frequency Boost Inverter Cascaded by Rectifier-Inverter System for PV Grid-Tie Applications
摘要： This paper proposes a new topology for a single-phase grid-tie two-stage DC-AC boost inverter for the application of PV systems that utilize high-frequency transformer (HFT) for galvanic isolation. In the first stage, a new single-stage high-frequency boost inverter (HFBI) is proposed to boost and convert the DC output voltage of the PV modules to a high-frequency single-phase square waveform and to realize maximum power point tracking (MPPT). The second stage is rectifier-inverter system (RIS) that interfaces HFBI to the grid. Therefore, a single-phase high-frequency transformer is used to link both stages and to provide galvanic isolation between the AC and DC sides. The proposed topology has many advantages such as increasing the inverter output voltage level, MPPT, high reliability, small size and lightweight. In addition, a proportional integral current control (PI) conventional is used to inject a sinusoidal current into the grid at unity power factor. The proposed topology has been verified analytically by using PSIM software and experimentally by using a laboratory prototype.
关键词： high frequency transformer,boost inverter,photovoltaic,grid connected
更新于2025-09-09 09:28:46
-
Calibration of the Absolute Linearity of Lock-In Amplifiers
摘要： This paper describes the development of a system capable to calibrate the absolute linearity of lock-in amplifiers in their 1-μV range for frequencies between 20 Hz and 1 kHz. The system is based on cascaded inductive voltage dividers that have been especially designed to maximize their input impedance and to have minimal influence on the previous stage. The cascaded topology reduces the uncertainty for very large ratios (>1000:1) and reaches measurement uncertainties below 1 nV at 10 μV.
关键词： lock-in amplifier,synchronous sampling,voltage ratio,Inductive voltage divider (IVD),linearity,transformer,very low ac voltage
更新于2025-09-09 09:28:46
-
Analysis of transformer less inverter for PV applications
摘要： To enhance the effectiveness and decrease the cost of a Photovoltaic (PV) system, the utilization of transformer less PV inverters is an option of expanding interest. In any case, this topology should be considered in detail, as it shows a few issues like effectiveness degradation and safety issues identified with the galvanic association between the system and the PV generator. In this research paper, a review of standalone and grid-connected PV inverter structures has been done. From one viewpoint, a few options in light of established structures have been introduced. At last parasitic capacitance in PV arrays and leakage current produced from PV systems are examined.
关键词： Grid Connected Systems,Parasitic Capacitance,Leakage Current,Photovoltaic,Transformer Less Inverters
更新于2025-09-04 15:30:14
-
[IEEE 2018 IEEE Energy Conversion Congress and Exposition (ECCE) - Portland, OR, USA (2018.9.23-2018.9.27)] 2018 IEEE Energy Conversion Congress and Exposition (ECCE) - 10 kW High Efficiency Compact GaN-Based DC/DC Converter Design
摘要： Gallium-nitride high-electron-mobility transistors (HEMTs) have shown their distinct advantages over silicon devices in the power converter design, including high switching speed, no reverse recovery loss, high switching frequency and compact package. This helps to build a high-efficiency and high-power-density 10 kW LLC resonant converter. A switching cell with two paralleled 650V 60A enhanced-mode GaN HEMTs are proposed including layout consideration and thermal management. The switching cell is adopted at the primary and secondary side separately in the converter. An integrated high frequency litz-wire transformer is presented with its optimization process. With the 3D package of the converter structure using the GaN-based switching cell and the litz-wire transformer, the converter achieves 97.9% peak efficiency under full power and 131 W/in3 (8 kW/L) power density.
关键词： Gallium nitride (GaN),litz wire,LLC resonant converter,transformer,DC/DC converter
更新于2025-09-04 15:30:14
-
A Comparative Topologies in Grid Connected Photo Voltaic System for Efficient Behavior
摘要： The power delivered by a PV system consisting of one or more photovoltaic cells is dependent on the irradiance, temperature, and the current drawn from the cells. Maximum Power Point Tracking (MPPT) is used to obtain the maximum power from these systems. Grid-tied inverters are the key components of distributed generation system because of their function as an effective interface between renewable energy sources and utility. In this paper, Perturb and Observe (P&O) and Incremental Conductance (IC) MPPT controllers are modeled and comparison is carried out. Recently, there has been an increasing interest in the use of transformer less inverter. The leakage current issues of transformer less inverter depends on the topology structure and modulation scheme, so it have to be addressed very carefully to meet the safety regulations. In order to eliminate the leakage current, OH5transformer less inverter topology is proposed and compared with switching inverter. The results concluded that using ICalgorithm the efficiency will improve comparatively. With the use of transformer less OH5 inverter along with ICalgorithm reduction in size and cost is observed. The improvement in efficiency with OH5 inverter is possible because of using five MOSFET switches. With usage of MOSFET switches switching losses and dead time is reduced. The leakage current is less in OH5 inverter compared to all other topologies proposed in reference. So isolation between grid and PV system is possible and safety of operating person is improved.
关键词： Transformer Less OH5 Inverter,Maximum Power Point Tracking (MPPT),Grid Tied Inverter,Boost Converter,Switching Inverter
更新于2025-09-04 15:30:14
-
[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Effects of Moisture on Surface Charge Behavior of Fluorinated Oil-impregnated Paper under DC and Pulse Voltages
摘要： The oil-paper insulation is widely implemented in converter transformer. Moisture has detrimental influence on the lifespan of oil-paper insulation. Meanwhile, the degradation velocity can be accelerated when the operating overvoltage occurs. Direct fluorination is an effective approach to modify the surface property of insulating material. Hence, for investigating the effects of moisture on charge behavior of fluorinated oil- impregnated paper under DC and pulse voltage, the specimens of being fluorinated for 5, 30 and 60 min respectively are treated in the sealed container with relative humidity of 20%, 40% and 60% for 30 min. From the research, conclusions can be drawn that the specimen of being fluorinated for 30 min has the best performance in water absorption. The moisture has less influence in modifying the deep trap depth of fluorinated paper and introduces more shallow traps. Meanwhile, the dissipating velocity becomes lager when the pulse frequency increases from 300 to 500 Hz. On the contrary, the velocity gets smaller when the frequency sequentially increases to 700 Hz.
关键词： oil-paper,moisture,surface charge,Converter transformer,pulse voltage
更新于2025-09-04 15:30:14
-
[IEEE 2018 IEEE PES Asia-Pacific Power and Energy Engineering Conference (APPEEC) - Kota Kinabalu, Malaysia (2018.10.7-2018.10.10)] 2018 IEEE PES Asia-Pacific Power and Energy Engineering Conference (APPEEC) - Transformer-less Single Phase H2D4 Inverter with Voltage Controller for Grid-tied PV System
摘要： Nowadays the transformer-less photovoltaic (PV) grid connected inverter is more popular because of its higher efficiency, compact size and lower cost. The issue of leakage current is a technical challenge, which needs to be controlled carefully. Moreover, many inverter topologies have been proposed to proficient the inverter to control the reactive power to a certain point in order to maintain the power factor (PF) close to one. In case of solar PV system, voltage fluctuation and synchronization with the utility grid is the challenging issue. Therefore, in this paper a new transformer-less inverter is proposed consisting of four diodes and two IGBT switches called H2D4 topology. The proposed topology can overcome the issue of leakage current by maintaining the common mode (CM) voltage constant while maintain low total harmonic distortion (THD) and higher PF. Because of the minimum number of IGBT switches, the leakage current and the conduction loss decrease. Besides, the size of the system is also decreased. Additionally, voltage fluctuation and synchronization are controlled by a newly proposed voltage controlled closed loop system where duty ratio is controlled. The proposed topology and the existing neutral point clamped (NPC) and H6 topologies are simulated in MATLAB/Simulink software, to clarify the theoretical analysis. It is found that the voltage controller closed loop control system of H2D4 inverter topology more efficiently control the voltage fluctuation problems while maintaining a low current THD with higher efficiency and high PF as compared with the system without control topology.
关键词： Grid connection,voltage synchronization,utility grid,total harmonic distortion,transformer-less inverter,power factor,leakage current,reactive power
更新于2025-09-04 15:30:14