944 results on '"dc current"'
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2. Comparative study on mechanism of DC and AC current on corrosion of copper–aluminium composites.
- Author
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Cheng, Yulin, Zhang, Yifan, Li, Zhengyuan, Tang, Xinyue, and Yuan, Xiaoguang
- Abstract
In this study, corrosion behaviours accelerated by neutral salt spray were thoroughly investigated on copper–aluminium composites with 3 wt% concentration NaCl for 72 h under DC and AC current respectively. The similarities and differences of the corrosion mechanism of the copper–aluminium composite under the two kinds of current were analysed by weight loss analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy and electrochemical detection methods. It can be concluded that there are two opposing influences of the current on the corrosive effects, including acceleration by the impressed current and inhibition by the heating effect. Of these, the inhibition effect on corrosion is more obvious, as the thermal effect of DC current is greater under the same current value. It is worth noting that the directional migration of ions caused by DC current will affect the degree of corrosion and the composition of the corrosion products on the surfaces of both sides of the samples, which is a unique characteristic not seen with AC current. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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3. Design of Two-Stage Differential Op-Amp with Frequency Compensation
- Author
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Akkaldevi, Anirudh Balaji, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Li, Yong, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Oneto, Luca, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zamboni, Walter, Series Editor, Tan, Kay Chen, Series Editor, Kumar Jain, Pradip, editor, Nath Singh, Yatindra, editor, Gollapalli, Ravi Paul, editor, and Singh, S. P., editor
- Published
- 2024
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4. Commutation Failure Predictive Control Based on Fast AC Voltage Measurement in LCC-HVDC
- Author
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Guodong Huang, Xiao Tian, Haibo Yuan, Xiaofeng Dong, Li Zhou, and Qing Wang
- Subjects
Commutation failure ,DC current ,HVDC ,predictively control ,extinction angle ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 - Abstract
To inhibit commutation failure (CF), in this paper, the influence factors of CF were analyzed, and considering different fault types and different valves, the mathematical expression of extinction angle was deduced. In addition, by analyzing existing control strategies for inhibiting CF, it is indicated that existing control strategies cannot quickly and accurately obtain the AC voltage amplitude and zero-crossing phase shift angle. To solve this problem, this paper proposed a fast AC voltage measurement method, and the zero-crossing phase shift angle can be calculated by AC voltage amplitude. On this basis, a commutation failure predictive control method (CFPCM) was proposed to inhibit CF. The CFPCM can adapt to all fault types. Finally, based on the CIGRE HVDC benchmark model, the commutation failure prevention module (CFPREV) and CFPCM simulation model were built using PSCAD/EMTDC to verify the effectiveness of the proposed CFPCM. The simulation results showed that the CFPCM can not only inhibit CF more effectively, but also reduce the fluctuation of DC current, AC voltage, and extinction angle with a fault occurred in the inverter AC system.
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- 2023
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5. Electric Current
- Author
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Blum, Michelle and Blum, Michelle
- Published
- 2022
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6. 基于直流电流动态上升的高压直流输电系统换相失败分析.
- Author
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苏常胜, 尹纯亚, and 李凤婷
- Subjects
FAILURE analysis ,ANGLES - Abstract
Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2023
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7. DC Current Rejection for Transformerless Grid-Connected Inverters
- Author
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Xiao, Huafeng, Wang, Xiaobiao, Chen, Wei, Series Editor, Chen, Yongzheng, Series Editor, He, Xiangning, Series Editor, Li, Yongdong, Series Editor, Liu, Jingjun, Series Editor, Luo, An, Series Editor, Ma, Xikui, Series Editor, Ruan, Xinbo, Series Editor, Shen, Kuang, Series Editor, Xu, Dianguo, Series Editor, Xu, Jianping, Series Editor, Xu, Mark Dehong, Series Editor, Zha, Xiaoming, Series Editor, Zhang, Bo, Series Editor, Zhang, Lei, Series Editor, Zhang, Xin, Series Editor, Zhao, Zhengming, Series Editor, Zheng, Qionglin, Series Editor, Zhou, Luowei, Series Editor, Xiao, Huafeng, and Wang, Xiaobiao
- Published
- 2021
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8. Ablative Therapy of Bypass Tracts, AV Junction, and AV Nodal Reentrant Tachycardia
- Author
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Gomes, J. Anthony and Gomes, J. Anthony
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- 2020
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9. Study of Inverter Open-Circuit Fault in Grid Connected Photovoltaic Systems: Influence on Output Power and Detection Method.
- Author
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Vu, H. G. and Ma, T. T. H.
- Subjects
PHOTOVOLTAIC power systems ,FAULT diagnosis - Abstract
The paper presents an investigation of single switch open-circuit fault in the inverter of photovoltaic (PV) systems. An IGBT two-level three-phase inverter which is used to connect the photovoltaic system to the main grid is considered in this application. First, the fault is created by modifying the control gate signal sent to the inverter. Second, the operation of a PV system is simulated under various levels of the irradiation under both healthy state and the condition of single switch open-circuit fault. The output powers generated by the system are then compared to show the influence of fault occurrence. Based on the DC current of the inverter, fault detection method is recommended. Investigation results show that the fault strongly affects the output power and that can be detected by judging the amplitude of three first orders of the AC side fundamental frequency. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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- View/download PDF
10. Pump–Probe Noise Spectroscopy of Molecular Junctions
- Author
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Ochoa, Maicol A, Selzer, Yoram, Peskin, Uri, and Galperin, Michael
- Subjects
dc current ,laser pulse pair sequence ,molecule−contact interface ,nonequilibrium Green function ,shot noise ,Physical Sciences ,Chemical Sciences - Abstract
The slow response of electronic components in junctions limits the direct applicability of pump-probe type spectroscopy in assessing the intramolecular dynamics. Recently the possibility of getting information on a sub-picosecond time scale from dc current measurements was proposed. We revisit the idea of picosecond resolution by pump-probe spectroscopy from dc measurements and show that any intramolecular dynamics not directly related to charge transfer in the current direction is missed by current measurements. We propose a pump-probe dc shot noise spectroscopy as a suitable alternative. Numerical examples of time-dependent and average responses of junctions are presented for generic models.
- Published
- 2015
11. A Sensorless Control Algorithm for the Circular Winding Brushless DC Motor Based on Phase Voltages and DC Current Detection.
- Author
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Jia, Zhewu, Zhang, Qinghu, and Wang, Dong
- Subjects
- *
BRUSHLESS electric motors , *CIRCUIT complexity , *POSITION sensors , *SENSOR placement , *VOLTAGE , *ELECTRIC motors , *TORQUE , *SQUARE waves - Abstract
Circular winding brushless dc (CWBLdc) motor is a novel square-wave multiphase permanent magnet motor with high torque density and excellent vibration performance. It has good prospect in high power and performance applications. However, the control of CWBLdc motor depends on a precise rotor position. Consequently, its application is restricted in some situations where it is difficult to install position sensors. In view of the fact that the existing sensorless control methods are not suitable for the novel CWBLdc motor, a sensorless control algorithm based on the phase voltages and dc current detection is proposed to obtain a continuous and precise rotor position. The fundamental harmonic amplitude of the phase current is estimated based on the dc current, which eliminates the process of phase currents detection and reduces the complexity of the circuit. The error of the algorithm is derived in detail and its accuracy is analyzed theoretically in the paper. The experimental results show that the performance of the proposed sensorless control algorithm is equivalent to that of control with position sensor. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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12. INVESTIGATION OF EFFECT OF WATER/CEMENT RATIO- DC CURRENT AND GRAPHENE OXIDE ON POROSITY-MATURITY AND ELECTRICAL CONDUCTIVITY OF HARDENED MORTARS.
- Author
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HOCAOĞLU, İSMAİL
- Subjects
MORTAR ,GRAPHENE oxide ,ELECTRIC conductivity ,CEMENT ,NANOSTRUCTURED materials ,NEW product development - Abstract
Today, materials are produced with nanotechnology, which are new products as a result of the development of technology. For cement-based composites, porosity is very important in terms of the strength and durability of the material after the material hardens. Today, with the innovations in technology, new materials are produced in the construction sector. New generation materials are produced on nano-meter scale using nanotechnology. These materials are used in cement-based composites to reduce porosity and improve durability properties. This research is aimed to reduce the porosity of the mortars by adding the nanomaterial graphene oxide (GO) to cement-based mortars whose sizes are 4cm x 4cm x 16cm. To investigate the effect of graphene oxide on porosity, series were produced as water/cement ratios are 0.55, 0.70, 0.90, and 1.00, by substituting 0.025 % GO in the mortars instead of cement. Besides, to investigate the effect of DC stress intensity on porosity, 25 V DC current is applied to all series. Mortar internal temperatures were measured from the beginning of hydration reactions in fresh mortars. Various comparisons have been made by calculating the maturity values of the mortars. Hardened mortars were cured for 7 and 28 days, then current passes on the mortars were measured by using an ampere meter. It has been investigated whether a relationship can be established between flow transfer and porosity. As a result of this study, the porosity of mortars can be reduced and maturity values can be increased by adding GO to cement-based mortars and applying DC current. In addition, porosity of cement-based materials can be estimated by using electrical methods. [ABSTRACT FROM AUTHOR]
- Published
- 2021
13. DC current control of a zero-sequence load using a diode rectifier for a three-phase four-wire motor drive system
- Author
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Yusuke FUJII, Junichi ASAMA, Akira CHIBA, and Hideaki FUJITA
- Subjects
magnetic levitation ,magnetic bearing ,three-phase four-wire system ,dc current ,zero-sequence current ,permanent magnet motor ,diode rectifier ,Mechanical engineering and machinery ,TJ1-1570 ,Engineering machinery, tools, and implements ,TA213-215 - Abstract
This paper describes the active DC current control of a zero-sequence load using a diode rectifier for a three-phase four-wire motor drive system, intended for application to (for example) a three-phase motor with an axial magnetic bearing. This motor drive system requires a three-phase inverter for rotation and a single-phase H-bridge inverter for magnetic suspension. To reduce the number of system components, the authors propose a unique current control method, where the suspension winding is connected between the neutral point of the Y-connected three-phase motor winding and the middle point of two split capacitors of the inverter. Such a wiring connection is called a three-phase four-wire system, and the current flowing in this suspension winding is defined as a zero-sequence current herein. Hence, only one three-phase inverter is required for the control of the three-phase motor current and single-phase magnetic suspension. However, the split capacitor voltages are unbalanced when DC current is provided to the zero-sequence load of the suspension winding because the capacitor voltage is proportional to the integral of the zero-sequence current. To supply DC current to the suspension winding and balance the split capacitor voltages, a novel circuit topology is proposed, where the diode rectifier circuit with suspension winding is connected to a zero-sequence load. When an AC current is provided to the zero-sequence load, a rectified current with a DC component is provided to the suspension winding, whereas the AC current flows in the split capacitors, thereby balancing the capacitor voltages. To verify the proposed DC current control, circuit simulations and experiments were performed. The experimental setup comprised a three-phase permanent magnet synchronous motor and a one-degree-of-freedom magnetic levitation. The test results show that the proposed method can provide a DC current to the suspension winding and control the magnetic levitation with balanced split capacitor voltages.
- Published
- 2020
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14. Annealing Effects on XLPE Insulation of Retired High-Voltage Cable
- Author
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Yue Xie, Yifeng Zhao, Gang Liu, Jiasheng Huang, and Licheng Li
- Subjects
XLPE ,DSC ,DC current ,dielectric breakdown strength ,dielectric spectrum ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 - Abstract
In this paper, the performance of several annealing methods on three retired cables and the annealing effects on the improvement in the thermal and electrical properties of cross-linked polyethylene (XLPE) insulation were discussed. The cable insulation layer was peeled, and the peels near the inner semi-conductive layer were used as the test samples. Isothermal treatment and heat recycling treatment were performed at temperatures of 85, 90, 95, and 100 °C, and the temperatures were held in the heat recycling treatment for 8, 16, and 24 h, respectively. Each heat recycling treatment was repeated 20 times, and the duration of the isothermal treatment was the same as that for the heat recycling treatment with a 24 h temperature holding hour. Then, Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were performed, and the dielectric spectrum, DC conduction current, and dielectric breakdown strength EB were measured. The results showed that damage involving molecular changes is linearly related to the cable service year. As the annealing temperature increases, the melting range and electrical conductivity decrease; the melting point, crystallinity, lamellar thickness, and dielectric breakdown strength increase; and the optimal values appear for the samples annealed at 95 °C. With an increased temperature holding hour, the peels annealed at 95 °C exhibit a decreased melting range and electrical conductivity and an increased crystallinity, melting point, lamellar thickness, and dielectric breakdown strength. As a result, the two different treatments are verified to effectively improve the thermal and electrical properties for the XLPE as early research on cable rejuvenation by heat treatment.
- Published
- 2019
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15. Measurement of the DC current based on magnetic fluids with an orthogonal magnetic field.
- Author
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Zhang, Jian-Ying, Che, Chuan-Qiang, Wang, Qiong, Xu, Da-Peng, and Yuan, Shuai
- Subjects
- *
MAGNETIC fluids , *DIRECT current power transmission , *MAGNETIC fields , *MAGNETIC particles , *PHOTOVOLTAIC power generation , *ROOT-mean-squares , *ELECTRIC potential measurement - Abstract
Measurement of DC current is critically important in a wide range of applications, such as in photovoltaic power generation and DC power transmission. In this paper, the DC current measuring method based on magnetic fluids with orthogonal magnetic fields is studied. Firstly, the induced voltage of measurement coil, which contains a series of harmonics and the amplitude of its fundamental component is 2.5 times larger than that of other components, is derived and analyzed. Then, influence factors of the induced voltage are systematically studied. As a result, with a DC component injection into the exciting current, the frequency of the induced voltage becomes a half of that without a DC component, and when the DC component reaches to or exceeds the amplitude of the AC component, the induced voltage nearly has no distortion. Finally, the input-output characteristic of the measurement method is examined, and the accuracy, measuring range, and sensitivity are discussed, indicating that the linearity of the foundamental component root mean square (RMS) value curve is better than the one of the voltage amplitude curve under the same DC current range, and the sensitivities of induced voltage amplitude and the fundamental component RMS value are 5.948 and 3.717 mΩ, respectively. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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16. Optimised damping control of islanded DC power systems using state feedback.
- Author
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Fu, Yuan, Li, Hao, Zhang, Xiangyu, and Wang, Yaoduo
- Subjects
- *
STATE feedback (Feedback control systems) , *POLE assignment , *VOLTAGE-gated ion channels , *EQUATIONS of state , *ELECTRIC power distribution grids - Abstract
The voltage oscillation of islanded DC-power systems is probably caused by negative impedance, produced by the converter from conventional power control structure. In this study, the small disturbance linearised state equation of a DC-power grid with constant power load is derived to estimate the damping characteristics of DC voltage. To enhance the transient voltage stability, a novel DC-voltage damping control method is proposed, where both DC voltage and DC current are used as state-feedback variables. Furthermore, two state-feedback control loops are designed to regulate the duty cycle of buck–boost converter added to the energy-storage device. Using the root-locus method, the principle of system pole placement is further discussed to determine the optimal control parameters in the proposed feedback loops, so that the damping characteristics of power system can be optimised. Finally, experimental tests are conducted on a hardware-in-the-loop platform of a typical islanded DC-power system to validate the new control structure. The results demonstrate that the DC-voltage oscillation can be reduced rapidly, which greatly improves the transient stability of DC-power system. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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- View/download PDF
17. Design and Performance Test of a 20-kV DC Superconducting Fault Current Limiter.
- Author
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Sun, Jianlong, Du, Jian, Li, Yan, Mo, Siming, Cai, Yuan, Yuan, Wen, and Ma, Tao
- Subjects
- *
SUPERCONDUCTING fault current limiters , *YTTRIUM barium copper oxide , *TEST design , *SHORT-circuit currents , *FAULT currents - Abstract
A resistive-type dc superconducting fault current limiter (SFCL) is developed for the fault current limiting at the Suzhou Nami substation. The rated voltage and current are 20 kV and 400 A, respectively. The prospective peak value of the short-circuit current is about 3.5 kA, and the current could be limited to less than 2.1 kA by the SFCL. The SFCL uses about 1800-m stainless steel reinforced yttrium barium copper oxide (YBCO) conductor. According to the testing results, the developed SFCL has passed the dc withstand voltage test at 50 kV/min, the full-wave lightning impulse voltage at 95 kV, and the dc power switching test with a peak value of 2.26 kA and a fault duration of 16.5 ms. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
18. Potline Open Circuit Protection
- Author
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Duval, Dominique, Jacon, Michel, Johnston, Andy, Lamant, Didier, Marcellin, Pierre, Mathevon, Roland, Troubat, Laurent, and Suarez, Carlos E., editor
- Published
- 2016
- Full Text
- View/download PDF
19. Commutation Failure Analysis and Prevention of UHVDC System With Hierarchical Connection Considering Voltage Harmonics
- Author
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Yongxin Xiong, Jinyu Wen, Wei Yao, Lingrao Wang, and Shi Zhongtuo
- Subjects
Dc current ,Coupling ,Computer science ,Control theory ,Harmonics ,Energy Engineering and Power Technology ,Commutation ,Transmission system ,Electrical and Electronic Engineering ,Fault (power engineering) ,Voltage ,Connection (mathematics) - Abstract
Although the harmonics interaction plays a vital role in causing commutation failure (CF) in an ultra HVDC (UHVDC) system with hierarchical connection, it has not been sufficiently considered in previous work. In this paper, the mechanism of CFs in UHVDC system with hierarchical connection is investigated via the analysis of harmonics interaction. The changes of the commutation condition in fault layer and non-fault layer in one cycle after the fault initiation are described and divided into several stages. Then the risk and dominant factors of the CF in each stage are identified. Moreover, a coordinated CF prevention scheme based on harmonics and DC current detection is proposed to mitigate the concurrent CF in UHVDC system with hierarchical connection. Finally, the effectiveness of the proposed scheme is verified via a 1100 kV UHVDC transmission system under different fault scenarios and various AC-side coupling strengths.
- Published
- 2022
- Full Text
- View/download PDF
20. Fast compensation of DC bus voltage drops using modular multilevel converters
- Author
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Christoph Stark, Dierk Danowski, Jose-Luis Marqués, and Claus Hillermeier
- Subjects
power grids ,power convertors ,HVDC power convertors ,power control ,voltage control ,modular MMCs ,DC grid ,modular multilevel converters ,fast control ,important requirement ,control design ,sudden DC voltage drop ,suitable pattern ,MMC internal circular currents ,DC current ,fast compensation ,DC bus voltage ,Engineering (General). Civil engineering (General) ,TA1-2040 - Abstract
For a DC grid using modular multi-level converters (MMCs) fast control of the DC bus is an important requirement. A control design is presented where a sudden DC voltage drop is compensated without any influence on the AC side. Using a suitable pattern in the MMC internal circular currents, the DC current can be adjusted and the MMC can be brought to a new steady state with symmetrised arm energies within few milliseconds.
- Published
- 2019
- Full Text
- View/download PDF
21. DC Current Distribution in Both AC Power Grids and Pipelines Near HVDC Grounding Electrode Considering Their Interaction.
- Author
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Zhang, Bo, Cao, Fangyuan, Zeng, Rong, He, Jinliang, Meng, Xiaobo, Liao, Yongli, and Li, Ruihai
- Subjects
- *
CURRENT distribution , *ELECTRIC power distribution grids , *NATURAL gas pipelines , *ELECTRIC power , *PIPELINES , *GAS distribution , *EARTH currents - Abstract
The dc current injected into the earth from the grounding electrodes of an HVdc system could flow into the ac electric power grids and gas pipelines through their grounding points. The dc current distribution either in ac power grids or in pipelines would be affected by each other. In this paper, a numerical approach to simulate the dc current distribution in ac power grids and gas pipelines considering the interaction is put forward. The approach is validated by field test. The dc current distribution in ac power grids and gas pipelines is discussed based on the calculation result in a real case. It is found that the effect of ac power grids on the current distribution in gas pipelines is greater than the effect of gas pipelines on the current distribution in ac power grids. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
22. Fast compensation of DC bus voltage drops using modular multilevel converters.
- Author
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Stark, Christoph, Danowski, Dierk, Marqués, Jose-Luis, and Hillermeier, Claus
- Subjects
CONVERTERS (Electronics) ,ELECTRIC power distribution grids ,DIRECT current power transmission ,ELECTRIC potential ,ELECTRIC currents - Abstract
For a DC grid using modular multi-level converters (MMCs) fast control of the DC bus is an important requirement. A control design is presented where a sudden DC voltage drop is compensated without any influence on the AC side. Using a suitable pattern in the MMC internal circular currents, the DC current can be adjusted and the MMC can be brought to a new steady state with symmetrised arm energies within few milliseconds. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
23. Transient current curvature based protection for multi‐terminal flexible DC distribution systems.
- Author
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Wang, Congbo, Jia, Ke, Bi, Tianshu, Xuan, Zhenwen, and Zhu, Rui
- Abstract
In a flexible DC distribution system, the converters will be blocked within a few milliseconds for its self‐protection during the DC line fault. Using such a short period of the fault transient, it is challenging to identify the correct faulted area. In this study, the characteristics of fault current waveform and sudden change are analysed in detail, and the curvature algorithm is used to extract the current waveform difference between the internal and external faults. Then this study proposes a new scheme for the multi‐terminal DC distribution system. This protection is developed based on natural variation characteristics and curvature of DC current under fault transients. Compared with the di/dt protection to correctly identify internal high impedance fault. The proposed method could identify faults with different high resistances quickly, meet the speed and reliability requirement of the DC distribution system. Numerous tests are carried out in both simulation and hardware experiments. Testing results derived under various fault conditions have demonstrated that internal faults with different impedances can be correctly identified by employing the proposed protection scheme. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
24. Influence of DC Current on Corrosion Behaviour of Copper–Aluminium Composite Plates
- Author
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Cheng, Yu-Lin, Zuo, Xiao-Jiao, Yuan, Xiao-Guang, Huang, Hong-Jun, and Zhang, Yi-Fan
- Published
- 2021
- Full Text
- View/download PDF
25. A Genetic-Algorithm-Based DC Current Minimization Scheme for Transformless Grid-Connected Photovoltaic Inverters
- Author
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Lei Song, Lijun Huang, Bo Long, and Fusheng Li
- Subjects
dc current ,grid-connected inverter ,genetic algorithm ,back-propagation neural network ,Technology - Abstract
Transformerless grid-connected inverters are of great industrial value in photovoltaic power generation. However, the direct current (DC) induced into the inverter’s output degrades the power quality of the grid. Recently, a back-propagation neural work proportional−integral−derivative (BP-PID) scheme has proven helpful in solving this problem. However, this scheme can be improved by reducing the suppressing time and overshoot. A genetic algorithm (GA)-based DC current minimization scheme, namely the genetic-algorithm-based BP-PID (GA-BP-PID) scheme, was established in this study. In this scheme, GA was used off-line to optimize the initial weights within the BP neural network. Subsequently, the optimal weight was applied to the online DC current suppression process. Compared with the BP-PID scheme, the proposed scheme can reduce the suppressing time by 59% and restrain the overshoot. A prototype of the proposed scheme was implemented and tested on experimental hardware as a proof of concept. The results of the scheme were verified using a three-phase inverter experiment. The novel GA-PB-PID scheme proposed in this study was proven efficient in reducing the suppressing time and overshoot.
- Published
- 2020
- Full Text
- View/download PDF
26. Fast AC reactor-based fault current limiters application in distribution network
- Author
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Hamid Radmanesh and Seyed Hamid Fathi
- Subjects
reactors (electric) ,fault current limiters ,power distribution protection ,power distribution faults ,fast AC reactor-based fault current limiters ,negligible voltage drop ,power system ,DC current ,DC reactor-based FCL ,DRFCL ,radial distribution networks protection ,ARFCL performance ,Matlab software ,fault operation modes ,point of common coupling voltage ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Electricity ,QC501-721 - Abstract
Almost all of the fault current limiters (FCLs) have a negligible voltage drop during normal operation mode of the power system and show considerable impedance during the fault period. In addition, the most of the FCLs employ a reactor to limit the fault current, which carrying a DC current and named DC reactor-based FCL (DRFCL) or carrying AC current named AC reactor-based FCL (ARFCL). Here, a novel ARFCL is introduced for radial distribution networks protection. Then, the ARFCL performance on the limitation of the fault current is compared with DRFCL in a simple radial distribution network. The MATLAB software is used to simulate both FCLs performance and their effect on the fault current. The laboratory prototype of the ARFCL is built and tested for the evaluation of the ARFCL performance during normal and fault operation modes. The simulation and experimental results show the superiority of ARFCL to control the fault current, fast, and set the point of common coupling voltage in an acceptable range.
- Published
- 2018
- Full Text
- View/download PDF
27. A Commutation Failure Prediction and Mitigation Method
- Author
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Yin Hanhang, Zhou Xiaoping, Lerong Hong, Xia Haitao, and Zhu Renlong
- Subjects
Dc current ,Renewable Energy, Sustainability and the Environment ,Computer science ,Control theory ,Control system ,Energy Engineering and Power Technology ,Inverter ,Transient (oscillation) ,Commutation ,Fault (power engineering) - Abstract
The mitigation of commutation failure (CF) depends on the accuracy of CF prediction. In terms of the large error of existing extinction angle (EA) calculation during the fault transient period, a method for CF prediction and mitigation is proposed. Variations in both DC current and overlap angle (OA) are considered in the proposed method to predict the EA rapidly. In addition, variation in critical EA and the effect of firing angle (FA) on both DC current and OA are considered in the proposed method to obtain the accurate FA order for the control system. The proposed method can achieve good performance in terms of CF mitigation and reduce reactive consumption at the inverter side when a fault occurs. Simulation results based on the PSCAD/EMTDC show that the proposed method predicts CF rapidly and exhibits good performance in terms of CF mitigation.
- Published
- 2022
- Full Text
- View/download PDF
28. Wireless traffic light controller
- Author
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Alisher Shakirovich Ismailov, Nilufar Abdurakhmonova, and Gayrat Orifjanovich Tojiboyev
- Subjects
Q1-390 ,wireless ,Science (General) ,microcontroller ,ComputerSystemsOrganization_MISCELLANEOUS ,dc current ,ComputerSystemsOrganization_COMPUTER-COMMUNICATIONNETWORKS ,Education (General) ,esp8266 ,L7-991 - Abstract
The increasing numbers of transportations are forcing to build new roads and traffic lights. Traditional traffic light implementation cost a lot of money. Traditional traffic light implementation contains the all four traffic lights must connect to traffic light control by wire [5]. And in some cases those connecting wire come through ditches which will cost extra spending. Another issue with traditional traffic light controller is it works with 220 voltages AC current which life threatening to human. Based on those issues, this paper proposes two main goals for modern traffic light controller. The development of traffic light that works wireless connection and traffic light work on DC current 24 voltages. In order to achieve this traffic light controller we use esp8266 microcontroller which it has wireless signal on up to 300 meter radius.
- Published
- 2021
29. Generalized Impedance Analysis and New Sight at Damping Controls for Wind Farm Connected MMC–HVdc
- Author
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Shan Liu, Hui Pang, Zhiyuan He, Ke Ji, Jie Yang, Guangfu Tang, and Zigao Xu
- Subjects
Dc current ,Sight ,Matrix (mathematics) ,Computer science ,Control theory ,Minor (linear algebra) ,Energy Engineering and Power Technology ,System stability ,Electrical and Electronic Engineering ,Stability (probability) ,Electrical impedance ,Analysis method - Abstract
The small-signal stability of wind farm connected MMC-HVdc systems has been widely studied by impedance analyses. However, it is generally difficult to calculate the poles of wind farm connected MMC-HVdc due to complex internal dynamics. Thus the existing impedance analysis methods usually assume that the studied subsystems are stable. In some special cases, the MMC-HVdc itself may be unstable but the wind farm connected MMC-HVdc may be still stable. If the poles of the subsystem are not calculated, these phenomenons can not be well revealed by impedance analysis. In order to address these special issues. This paper divides the wind farm connected MMC-HVdc into three subsystems and proposed a 3-order minor loop-gain matrix to investigate the unified stability of both ac and dc systems. Based on the proposed model, the impact of ac/dc current-based damping controls in wind farm side MMC on the system stability are investigated. As a result, the proposed model makes up for the deficiencies in ac/dc impedance analysis method and provides a new sight at evaluating the impact of active damping controls on system stability. The simulation results in PSCAD/EMTDC validate the proposed models and stability analyses.
- Published
- 2021
- Full Text
- View/download PDF
30. Investigation of biasing conditions and energy dissipation in electrochemically controlled capillarity liquid metal electronics.
- Author
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Wang, Meng, Lei, Wen Tai, Dong, Jian, Dickey, Michael D., and Adams, Jacob J.
- Abstract
This Letter investigates the trade‐off between the biasing conditions (biasing current and electrolyte concentration) and energy dissipation in high‐frequency liquid metal electronics using electrochemically controlled capillarity (ECC). ECC can control the interfacial tension of liquid metal via DC current as a method to move the metal in capillaries. It requires a conductive electrolyte to facilitate the electrochemical reactions. Here, the authors measure the withdrawal rate of liquid metal under different biasing currents and electrolyte concentrations. The results indicate that a larger biasing current and a more concentrated electrolyte induce a faster withdrawal motion of liquid metal. This Letter also explores the change of antenna efficiency when different electrolyte concentrations are chosen. The selection of electrolyte concentration for high‐antenna efficiency conflicts with the need for fast withdrawal speed and low‐DC power consumption of the liquid metal system, therefore requiring a balance among the various parameters when ECC is applied in practical liquid metal electronics. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
31. Operating Cycle Performance, Lost Periodicity, and Waveform Distortion of Switch-Mode Power Supplies.
- Author
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Xu, Xiao, Collin, Adam J., Djokic, Sasa Z., Langella, Roberto, and Testa, Alfredo
- Subjects
- *
POWER resources , *DIRECT currents , *ELECTRIC currents , *ELECTRIC potential , *VOLTAGE regulators - Abstract
This paper investigates the performance of switch-mode power supplies used in desktop PCs (PC-SMPS’) across the entire range of operating powers. Experimental results show that at low to medium operating powers, the input ac current might lose its periodicity with supply voltage frequency, when PCS-MPS’ can be an unexpected source of interharmonics and dc component. In such cases, there is a significant increase of PC-SMPS’ current waveform distortion and a substantial decrease of efficiency and operational power factors, which requires application of appropriate measurement and calculation procedures during the analysis. To correctly assess these power-dependent changes in performance and power quality indicators, this paper introduces a novel testing and evaluation methodology, based on the known or assumed PC-SMPS operating cycle. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
32. Electrical and Thermal Co-Design for High-Power FPGA Packages.
- Author
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Shi, Hong, Tan, Siow Chek, Ahn, Jae-Gyung, Refai-Ahmed, Gamal, and Ramalingam, Suresh
- Subjects
- *
FIELD programmable gate arrays , *ELECTRODIFFUSION , *DIELECTRIC breakdown , *TEMPERATURE distribution , *ELECTRIC currents ,DESIGN & construction - Abstract
This paper describes a systematic approach to design field-programmable gate array (FPGA) package for high-power applications. As the power consumption is up to multihundred watts, not only the heat dissipation becomes a challenge, but the temperature-induced reliability concerns also mount up in the high current and noise-sensitive packages. Two most profound phenomena are substrate electromigration (EM) and package decoupling capacitor time-dependent dielectric breakdown (TDDB). The impact of EM is on maximum current-carrying capability, and impact of TDDB is on voltage noise suppression capability. However, we find both traditional static way of EM calculation and the legacy design considerations are oversimplified and insufficient for high-power products. In this paper, we report an enhanced methodology to derive substrate EM failure rate from composite current and temperature distributions. Moreover, we incorporate capacitor TDDB into the design flow to optimize capacitor lifetime for effective voltage noise suppression. In the end, we apply the electrical and thermal co-design to a 16-nm, 200-A, high-power FPGA meeting all current and dynamic noise specifications. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
33. Turn-to-Turn Contact Resistance Measurement of No-Insulation REBCO Pancake Coil: External Field Dependence
- Author
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Daisuke Nishikawa, Takanobu Mato, So Noguchi, Shunpei Mori, Ryota Inoue, Kohei Miyamoto, Hiroshi Ueda, SeokBeom Kim, and Takahiro Tatsuta
- Subjects
Superconductivity ,Materials science ,turn-to-turn contact resistance measurement ,Contact resistance ,Condensed Matter Physics ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,Dc current ,Electromagnetic coil ,Magnet ,0103 physical sciences ,Turn (geometry) ,External field ,No-insulation winding technique ,Electrical and Electronic Engineering ,Current (fluid) ,Composite material ,010306 general physics ,REBCO pancake coil - Abstract
The characteristics of no-insulation high-temperature superconducting (HTS) manet is dominated by the magnitude of the turn-to-turn contact resistance. A few techniques have been proposed to increase the turn-to-turn contact resistance. The relation between the turn-to-turn contact resistance and the magnet stability has also been investigated in simulations. Although the turn-to-turn contact resistance measurement was only the sudden-discharging method before, we proposed a low-frequency-AC current (LFAC) method. Using our proposed method, it is possible to measure the turn-to-turn contact resistance under various conditions. In a previous paper, we measured it when charging DC current to a single pancake coil. In this paper, the turn-to-turn contact resistance was measured by the LFAC method when an external field of 1-3 T was applied to a single pancake coil. The coil strain was also measured, and the relation of the turn-to-turn contact resistance and the coil strain was also discussed.
- Published
- 2021
- Full Text
- View/download PDF
34. Numerical Simulation of the Effect of a DC Electric Field on Seismic Wave Propagation with the Pseudospectral Time Domain Method
- Author
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Liu, Lanbo, Xiao, Lei, Liu, Hong, Yan, Hongrui, Yin, Xiang-chu, editor, Mora, Peter, editor, Donnellan, Andrea, editor, and Matsu’ura, Mitsuhiro, editor
- Published
- 2006
- Full Text
- View/download PDF
35. Extension of ZVS Region of Series–Series WPT Systems by an Auxiliary Variable Inductor for Improving Efficiency
- Author
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Min Zhang, Ruikun Mai, Yong Li, Zhengyou He, Shunpan Liu, Xiao Zhu, and Jiefeng Hu
- Subjects
Computer science ,020208 electrical & electronic engineering ,Equivalent series inductance ,Automatic frequency control ,02 engineering and technology ,Inductor ,Inductive coupling ,Electromagnetic interference ,Inductance ,Dc current ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Wireless power transfer ,Electrical and Electronic Engineering ,Voltage - Abstract
To maintain a stable output voltage under various operating conditions without introducing extra dc/dc converters, phase-shift (PS) control is usually adopted for wireless power transfer (WPT) systems. By using this method, however, zero-voltage switching (ZVS) operation cannot be guaranteed, especially in light-load conditions. To achieve high efficiency and reduce electromagnetic interference, it is significant for WPT systems to achieve ZVS operation of all switching devices in the whole operation range. In this article, an auxiliary variable inductor, of which the equivalent inductance can be controlled by adjusting the dc current in its auxiliary winding, is designed for series–series-compensated WPT systems under PS control to mitigate the loss arising from hard switching. As a result, a wide ZVS operation range of all switching devices can be achieved. A laboratory prototype is built to verify the theoretical analysis. The experimental results show that, under load and magnetic coupling variations, ZVS operation at fixed operation frequency as well as a constant dc output voltage can be maintained. Compared to the conventional method with only PS control, the proposed WPT can achieve higher overall efficiency in a wider load range owing to the wide ZVS operation range.
- Published
- 2021
- Full Text
- View/download PDF
36. Molded Case Electronically Assisted Circuit Breaker for DC Power Distribution Systems
- Author
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Yuanfeng Zhou, Yanjun Feng, Zheng John Shen, Slobodan Krstic, and Xin Zhou
- Subjects
Form factor (electronics) ,Computer science ,business.industry ,Electrical engineering ,Process (computing) ,Fault (power engineering) ,Power (physics) ,Dc current ,Commutation ,Electrical and Electronic Engineering ,business ,Low voltage ,Galvanic isolation ,Circuit breaker - Abstract
This article introduces a new dc hybrid circuit breaker (HCB) concept termed electronically assisted circuit breaker (EACB). A conventional ac mechanical molded case circuit breaker (MCCB) is used to interrupt dc fault currents with the assistance of an electronic commutation circuit, which is activated for a short time period only during the late phase of the breaking process. Unlike other prior art HCB concepts, the EACB uses a conventional thermal-magnetic MCCB baseline design with minimal modification on the actuation mechanism, arc chamber, or form factor, and uses an electronic commutation circuit, which only needs to commutate a fault current far below its peak value for a very short duration (∼100 μ s), both contributing to significant cost savings. Other advantages of the EACB concept include self-powered and autonomous operation, simple installation, inherently low on-resistance, and galvanic isolation. While an EACB does not facilitate arc-free or ultrafast breaking, it does provide a simple and cost-effective way to enhance the dc current interruption capability of the conventional ac MCCBs, which currently dominate the low voltage circuit breaker market. The EACB concept has been validated both experimentally and by simulation. Several 600Vdc/250A (nominal) EACB prototypes are designed and tested. They have experimentally demonstrated a fault current interruption capability of over 8000 A at a dc voltage of 600 V within 6 ms.
- Published
- 2021
- Full Text
- View/download PDF
37. Modeling the Impact on Wheel Sensor Readouts by Eddy Current Brakes Installed in High-Speed Trains
- Author
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Jon del Portillo, Gavin Lancaster, Kizkitza Gurruchaga, Wilhelm Baldauf, Kami Pars Benli, Henry Lehmann, Daniel Valderas, Oliver Stark, and J.I. Sancho
- Subjects
Microwave studio ,Test bench ,Traverse ,Computer Networks and Communications ,Computer science ,Aerospace Engineering ,Eddy current brake ,Temperature measurement ,Automotive engineering ,Dc current ,Automotive Engineering ,Drop (telecommunication) ,Train ,Electrical and Electronic Engineering - Abstract
This paper presents a model to anticipate the impact of Eddy Current Brakes (ECBs) installed in high-speed trains on the readouts of rail-side wheel sensors. The purpose is to anticipate false positive readouts of train wheels when traversing, one of the main obstacles for full ECB deployment. The ECB type EWB 154 from Knorr-Bremse and Wheel Sensor types RSR180 and RSR123 from Frauscher Sensor Technology are represented in a comprehensive model, integrating LTSpice and CST Microwave Studio. The wheel sensor predicted readout error is 4% compared to measurements when DC current is not applied to the ECB (passive case). It is demonstrated that the RSR180 is not compatible with ECBs, whereas the RSR123 is. The impact of active (DC current fed) brakes is analyzed when performing running tests with a high-speed ICE 3 train equipped with ECBs. The model is adjusted to study the saturation of the rail and ECB pole cores. The extra damping of the wheel sensor fingerprint is modeled by an extra 6% drop that may well be applicable to passive tests in a laboratory setting to shift to active tests without actually performing them. In this way, cost and time would be saved. Based on the model outcomes, a test bench is recommended for laboratory tests to emulate active behavior.
- Published
- 2021
- Full Text
- View/download PDF
38. Interlaboratory comparisons of calibration results of a multifunctional calibrator of electrical quantities
- Author
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Denys Nikitenko, Vasyl Dovhan, and Dmytro Shynder
- Subjects
Dc current ,Ac current ,Dc voltage ,Computer science ,Measuring instrument ,Calibration ,Electronic engineering ,Reference laboratory ,Voltage - Abstract
Article is dedicated to organization and conduct of the calibration results of reciprocal interlaboratory comparisons for the multifunctional calibrator of electric quantities: DC voltage, AC voltage, DC current and AC current. The interlaboratory comparisons of electric quantities measurement instruments calibration results are represented. Evaluation of the laboratory calibration results bias is provided using the modified criterion. Analysis and conclusions concerning participating laboratory competence are provided.
- Published
- 2021
- Full Text
- View/download PDF
39. Influence of DC Current on Movement of Dislocations in P-Silicon Single Crystals in Field of Internal Stresses
- Author
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Artem V. Kulagin, Alexander A. Solovyev, and Vladislav V. Rybin
- Subjects
010302 applied physics ,Materials science ,Condensed matter physics ,Field (physics) ,Silicon ,Movement (music) ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Dc current ,chemistry ,0103 physical sciences ,General Materials Science ,Electric current ,0210 nano-technology - Abstract
The behavior of linear defects in p-type silicon (111) carrying a direct current of density 0−15×105 A/m2 in the [110] direction are studied in the temperature range T=850–1000 K during isothermal annealing. The regularities of change in the linear density and maximum path of dislocations in slip lines are revealed. A model of linear defects displacement in silicon single crystals in the field of internal stresses under an electric current is proposed. Matching theory with experimental data has made it possible to reveal the dependence of this distribution on the internal stresses relaxation time.
- Published
- 2021
- Full Text
- View/download PDF
40. Coupled-Inductor-Based DC Current Measurement Technique for Transformerless Grid-Tied Inverters.
- Author
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Abdelhakim, Ahmed, Mattavelli, Paolo, Yang, Dongsheng, and Blaabjerg, Frede
- Subjects
- *
ELECTRIC inverters , *ROTARY converters , *ELECTROMAGNETISM , *PHOTOVOLTAIC cells , *ELECTRIC transformers - Abstract
Grid-tied photovoltaic inverters must fulfill several requirements, including high efficiency and reduced cost and complexity of the overall system. Hence, transformerless operation is advantageous in order to achieve the prior requirements. Meanwhile, such operation results in several demerits, such as the dc current component injection into the grid. This component should be effectively mitigated in order to avoid some impacts, such as the saturation of the transformers in the distribution network. On the other hand, limiting this component up to few milliamperes is a challenging issue due to the various measurement errors. Accordingly, different blocking and measurement techniques have been proposed and studied to overcome this issue, where some demerits are seen behind each technique such as the implementation complexity, the common-mode voltage problems, and the high filter requirements. Moreover, none of them measures the dc component directly, but predicts its value using different approaches. Hence, this letter proposes a new technique to measure this dc current component with high accuracy using a coupled inductor combined with a small-range Hall effect current sensor in order to achieve the lowest possible cost with the highest possible accuracy. The proposed technique is introduced, analyzed, and tested experimentally to verify its principle of operation. Also experimental measurement of the dc current component using a 5-kVA transformerless grid-tied voltage-source inverter is introduced with and without the proposed technique in order to validate its operation. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
- Full Text
- View/download PDF
41. Two Full Parameter Identification Methods for Synchronous Machine Applying DC-Decay Tests for a Rotor in Arbitrary Position.
- Author
-
Maurer, Frederic, Xuan, Mai Tu, and Simond, Jean-Jacques
- Subjects
- *
PARAMETER identification , *ROTORS , *ELECTRIC circuits , *REACTANCE (Electricity) , *DIRECT currents - Abstract
The main obstacle to a wide use of dc-Decay tests lies in the necessity to align the rotor with the $d$- or q$ -axis, which is very difficult to perform for high-power units. The goal of this paper is to propose and validate standstill dc-Decay measuring methods for a rotor in arbitrary position, which consist of generalizations of the existing methods with the rotor aligned with one axis. The first new method (dc-Decay I) delivers the equivalent circuit with a few measurements. The second new method (dc-Decay II) permits to determine the full equivalent circuit of both axes by performing only one measurement, which is unique and a breakthrough in parameter identification. The field current measurement enables obtaining the characteristic reactance x_{c}. A new method (dc-Decay III) is used to get the rotor angle. To extract the time constants and the reactances, an enhancement of the existing parameter identification algorithms using curve fitting is presented (used for the dc-Decay I method). Simulation and experimental results validate as good as possible the new methods and show their accuracy as well as their drawback. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
42. DC current prediction and suppression control strategies for inhibiting commutation failure in LCC-HVDC.
- Author
-
Yin, Chunya and SU, Changsheng
- Subjects
- *
ELECTRIC current rectifiers , *FORECASTING , *MATHEMATICAL models - Abstract
• DC current prediction method. • A coordination and prediction control strategies for inhibiting commutation failure. • DC current limit method. Aiming at the problem of the commutation failure (CF) of inverter caused by AC system fault, firstly, based on the commutation process, the extinction angle mathematical model considering the DC current at the beginning and ending of commutation process is established. Secondly, based on the DC transmission equivalent circuit, the analytical expression of DC current is deduced and established, based on this, a DC current prediction method at the end of commutation considering the change of overlap angle is proposed. Thirdly, at the inverter side, a CF prediction and suppression control strategy is proposed, at the rectifier side, a DC current limit control strategy based on the constant current controller is proposed, on this basis, a coordination and prediction control strategies (CFCCS) for inhibiting CF is proposed, which do not rely on the communication between rectifier and inverter. Finally, based on PSCAD/EMTDC and CIGRE HVDC model, the simulation model of CFPREV and CFCCS is built, the simulation results of different cases show that the proposed method can accurately predict the DC current, and the CFCCS not only can effectively reduce the risk of CF, also can inhibit the DC current rise caused by an AC system fault. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
43. Overview of Transformerless Photovoltaic Grid-Connected Inverters
- Author
-
Huafeng Xiao
- Subjects
Computer science ,020208 electrical & electronic engineering ,Photovoltaic system ,02 engineering and technology ,Grid ,law.invention ,Dc current ,Capacitor ,law ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Electrical and Electronic Engineering ,Transformer ,Voltage ,Leakage (electronics) - Abstract
Transformerless grid-connected inverters (TLI) feature high efficiency, low cost, low volume, and weight due to using neither line-frequency transformers nor high-frequency transformers. Therefore, TLIs have been extensively investigated in the academic community and popularly installed in distributed photovoltaic grid-connected systems during the past decade. This article analyzes and summarizes the state of the art of TLI techniques, three rules of maintaining constant common-mode voltage (CMV) of TLIs at switching frequency have been concluded from a generic CMV analysis model at the beginning. Second, suppression methods of leakage current (LC) and dc current injection (DCCI), so-called two key challenges for first-generation TLIs, have been classified and discussed in detail, respectively. Finally, future trends and some challenges of TLIs based on wide bandgap devices named second-generation TLIs have been presented in this article.
- Published
- 2021
- Full Text
- View/download PDF
44. An improved DC current flow controller with double quadrants operation and fault isolation capability
- Author
-
Xiao-Ping Zhang, Feng Shihua, Puyu Wang, Pengcheng Liu, Shan Liang, and Lizi Luo
- Subjects
Droop control ,business.industry ,Computer science ,020209 energy ,Fault isolation ,02 engineering and technology ,Modular design ,Improved DC current flow controller (I-DCCFC) ,Grid ,Fault detection and isolation ,Dc current ,Power flow ,Double quadrants operation capability ,General Energy ,Meshed multi-terminal DC (M2TDC) grid ,020401 chemical engineering ,Control theory ,Scalability ,0202 electrical engineering, electronic engineering, information engineering ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,0204 chemical engineering ,business ,Dc fault ,lcsh:TK1-9971 - Abstract
The DC current flow controller (CFC) has capability of enhancing the control freedom of current/power flow in multi-terminal DC (MTDC) grids and solving the barrier of uncontrollability of DC branch currents. The control margins of the DC branch currents can be further improved if the power flow reversal is achieved with the DC CFC. An improved DC CFC (I-DCCFC) utilized in the meshed MTDC (M2TDC) grid is investigated with three contributions: (1) Regarding a traditional DC CFC (T-DCCFC), its operational mode and operating principle are analysed. The fact that T-DCCFC only has singular quadrant operation capability, which constrains the power flow reversal, is explained. (2) The I-DCCFC with double quadrants operation capability is presented. Its operating principle with power flow reversal capability is analysed. (3) Based on the control strategy of the T-DCCFC, the control strategy of the I-DCCFC is developed and the ability to isolate the DC fault is analysed. The simulation model of a three-terminal M2TDC grid with the I-DCCFC is established in PSCAD/EMTDC. The effectiveness of the I-DCCFC in controlling the DC branch currents with power flow reversal capability and fault isolation under the fault condition is verified by the simulation results. As the I-DCCFC inherits the modular design concept with strong scalability, it can be expanded into an improved multi-line DC CFC according to the actual demands.
- Published
- 2020
45. Current Balancing Control Methods Using Advanced Carrier-Based Modulation for Five-Level Current Source Rectifiers
- Author
-
Lisandra Kittel Ries and Marcelo L. Heldwein
- Subjects
Harmonic analysis ,Dc current ,Computer science ,Modulation ,Electronic engineering ,Electrical and Electronic Engineering ,Current source ,Current (fluid) ,Inductor ,Control methods - Abstract
In an ideal ac–dc five-level current source multilevel converter, the dc current is equally divided between the two converters connected in parallel. However, current imbalances occur due to the nonidealities of the system, making the current balancing control to improve the multilevel converter performance. This article proposes two different methods for dc current balancing control for a five-level current source rectifier using an advanced carrier-based modulation strategy implemented through three different modulation patterns. A 6-kW prototype is constructed to demonstrate the current balancing control and a comparison among the methods is presented.
- Published
- 2020
- Full Text
- View/download PDF
46. PENGEMBANGAN ALAT UKUR BATAS KAPASITAS TAS SEKOLAH ANAK BERBASIS MIKROKONTROLER
- Author
-
Novia Utamu Putri, Risky Setiawan, and Putri Oktarin
- Subjects
Dc current ,Ac current ,Cause injury ,Computer science ,Buzzer ,Keypad ,Wearable computer ,Simulation ,Backpack - Abstract
Backpacks are often used by school children as a container or a place to carry their school materials and equipment, so these types of backpacks are very popular with school children. The large number of students wearing backpacks to school can be proven from the results of a survey conducted at SD N Bumisari, Natar District, South Lampung. Of the total number of subjects, 456 elementary school students carried 404 students (88.6%), and 52 students (11.4%) carried sling bags. But they rarely pay attention to the weight of the burden on the bag he carries everyday which turns out to cause injury to back pain.The tool is made in the form of a wearable device where the tool is in the form of a backpack that can be carried anywhere without having to require AC current as input voltage to the tool, because the power uses DC current with a voltage of 5V, the device is made using a microcontroller supported by a 10 kg loadcell sensor, modules HX711, keypad, plus an indicator component in the form of a buzzer. If the bag load exceeds the safe limit, the buzzer indicator will sound.
- Published
- 2020
- Full Text
- View/download PDF
47. Superconducting Transformer for Superconducting Cable Testing up to 45 kA
- Author
-
Hui Yu and Jun Lu
- Subjects
Superconductivity ,Physics - Instrumentation and Detectors ,Materials science ,Physics::Instrumentation and Detectors ,Condensed Matter - Superconductivity ,FOS: Physical sciences ,Instrumentation and Detectors (physics.ins-det) ,Superconducting magnet ,Condensed Matter Physics ,Engineering physics ,Electronic, Optical and Magnetic Materials ,law.invention ,Superconductivity (cond-mat.supr-con) ,Dc current ,law ,Condensed Matter::Superconductivity ,Astrophysics::Solar and Stellar Astrophysics ,Electrical and Electronic Engineering ,Transformer - Abstract
A facility capable of testing superconducting cables with current of tens of kA is essential for the development of large superconducting magnets. A superconducting transformer (SCT) is a suitable choice as a high DC current source for testing superconducting cables. In this work, we will present our experimental results of a SCT up to output current of 45 kA. The properties of this SCT is characterized at 4.2 K. Its behaviors during quenches at different current levels are studied., 4 pages, 6 figures
- Published
- 2020
- Full Text
- View/download PDF
48. Inflection Phenomenon in Cryogenic MOSFET Behavior
- Author
-
Arnout Beckers, Christian Enz, and Farzan Jazaeri
- Subjects
interface traps ,Materials science ,mosfet ,Gaussian ,01 natural sciences ,law.invention ,Dc current ,symbols.namesake ,law ,0103 physical sciences ,MOSFET ,cryogenic ,Electrical and Electronic Engineering ,Drain current ,010302 applied physics ,cmos technology ,Condensed matter physics ,Transistor ,temperature ,disorder ,Gate voltage ,Electronic, Optical and Magnetic Materials ,band tail ,CMOS ,symbols ,cryo-cmos ,inflection ,transistors - Abstract
This brief reports the analytical modeling and measurements of the inflection in the MOSFET transfer characteristics at cryogenic temperatures. Inflection is the inward bending of the drain current versus gate voltage, which reduces the current in weak and moderate inversion at a given gate voltage compared to the drift-diffusion current. This phenomenon is explained by introducing a Gaussian distribution of localized states centered around the band edge. The localized states are attributed to disorder and interface traps. The proposed model allows to extract the density of localized states at the interface from the dc current measurements.
- Published
- 2020
- Full Text
- View/download PDF
49. Comprehensive study of electrokinetic-assisted phytoextraction of metals from mine tailings by applying direct and alternate current
- Author
-
Rodriguez, Luis, Medina-Diaz, H.L, López-Bellido Garrido, Francisco Javier, Alonso Azcárate, Jacinto, and Fernandez Morales, Francisco Jesus
- Subjects
Mine tailings ,General Chemical Engineering ,Corriente continua ,Corriente alterna ,Electrokinetic-assisted phytoextraction ,Metals ,Fitoextracción electrocinética asistida ,Ballico ,Metales ,Electrochemistry ,DC current ,Ryegrass ,Residuos mineros ,AC current - Abstract
Electrokinetic-assisted phytoextraction (EKPH) involves the use of electric current to improve the mobilization of metals in soils and, therefore, their removal efficiency. It emerges as an interesting sustainable technology for the rehabilitation of abandoned mining areas. The goal of this research was to conduct a comprehensive study of this technique applied to real mine tailings from an abandoned Pb/Zn mine by using ryegrass as plant species and two types of electric current: direct with polarity reversal (DC-PR) and alternate (AC). The EKPH tests were conducted in specially designed plastic containers that allowed recording the main parameters of the electrokinetic process and sampling the different matrices studied, i.e. water, soil and plants. This intensive sampling program allowed detailed monitoring of the metal mobilization processes for the different treatments applied. The changes caused in metal mobility and physicochemical parameters of the tailings due to the application of electric current were reflected to a greater extent in the water samples than in solid ones. Accumulation of Pb, Zn, Cd and Cu in ryegrass tissues increased significantly by 41%, 17%, 34% and 32% when applying 1 V cm−1 of AC current, with respect to the results of phytoextraction without electric current. The application of DC-PR current did not lead, in general, to statistically significant increases in the plant metal uptake. These findings were adequately correlated with the changes found in the metal concentrations of soil pore water and, to a lesser extent, with those observed from the BCR sequential extraction applied to tailings samples., La fitoextracción electrocinética asistida (EKPH) implica el uso de corriente eléctrica para mejorar la movilización de metales en suelos y, por tanto, su eficiencia de eliminación. Surge como una interesante tecnología sostenible para la rehabilitación de zonas mineras abandonadas. El objetivo de esta investigación fue realizar un estudio exhaustivo de esta técnica aplicada a estériles mineros reales procedentes de una mina abandonada de Pb/Zn utilizando ryegrass como especie vegetal y dos tipos de corriente eléctrica: continua con inversión de polaridad (DC-PR) y alterna (AC). Los ensayos EKPH se realizaron en recipientes de plástico especialmente diseñados que permitieron registrar los principales parámetros del proceso electrocinético y muestrear las distintas matrices estudiadas, es decir, el agua, el suelo y las plantas. Este programa intensivo de muestreo permitió un seguimiento detallado de los procesos de movilización de metales para los diferentes tratamientos aplicados. Los cambios provocados en la movilidad de los metales y en los parámetros fisicoquímicos de los estériles debido a la aplicación de corriente eléctrica se reflejaron en mayor medida en las muestras de agua que en las sólidas. La acumulación de Pb, Zn, Cd y Cu en los tejidos de ryegrass aumentó significativamente en un 41%, 17%, 34% y 32% al aplicar 1 V cm-1 de corriente AC, respecto a los resultados de la fitoextracción sin corriente eléctrica. La aplicación de corriente DC-PR no condujo, en general, a incrementos estadísticamente significativos en la captación de metales por la planta. Estos resultados se correlacionaron adecuadamente con los cambios encontrados en las concentraciones metálicas del agua de poro del suelo y, en menor medida, con los observados a partir de la extracción secuencial BCR aplicada a muestras de estériles.
- Published
- 2023
- Full Text
- View/download PDF
50. Anomalous Behaviors of Non-Resonant Microwave Absorptions of High-Tc Superconductors
- Author
-
Sugawara, Kazushi, Arai, Nobuhito, Ichimura, Susumu, Naoi, Hideki, Hirose, Haruo, Yamashita, Tsutomu, editor, and Tanabe, Kei-ichi, editor
- Published
- 2000
- Full Text
- View/download PDF
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