Topic
Electrical impedance
About: Electrical impedance is a research topic. Over the lifetime, 36015 publications have been published within this topic receiving 371891 citations. The topic is also known as: electrical impedance & complex impedance.
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01 Jan 2002
TL;DR: In this paper, a deconvolution method was developed and implemented that yields these characteristic distribution patterns directly from the impedance spectra, and a general strategy for the identification of the reaction mechanisms was given.
Abstract: The polarization processes occurring at the electrode-electrolyte interfaces of solid oxide fuel cells (SOFC) were investigated by electrochemical impedance spectra measured at single cells under realistic operating conditions. The approach presented is based on distributions of relaxation times which are the basic quantity of interest in electrochemical impedance data analysis. A deconvolution method was developed and implemented that yields these characteristic distribution patterns directly from the impedance spectra. In contrast to nonlinear least squares curve fit of equivalent circuit models, no a priori circuit choice has to be made. Even more importantly, the excellent resolving capacity allows the untangling of the impedance contributions of up to three physically distinct processes within one frequency decade. With the method, processes with the highest polarization losses can be identified and targeted to improve cell performance. Based on the distributions, a general strategy for the identification of the reaction mechanisms is given. The evaluation of the distributions in terms of peak parameters is illustrated by a physical model for oxygen reduction at the SOFC cathode-electrolyte interface. The method is expected to find many applications in electrochemistry beyond the field of solid oxide fuel cell development.
408 citations
TL;DR: In this paper, an impedance shaping method is proposed with virtual impedances, and the current control loop can be designed independently under the practical considerations, which can work stably over a wide range of the typical inductive resistive grid impedance and exhibit strong rejection ability of grid-voltage harmonics.
Abstract: The current-controlled grid-connected inverter with LCL filter is widely used in the distributed generation system (DGS), due to its fast dynamic response and better power quality features. However, with the increase of power injected into the grid, control performances of the inverter will be significantly influenced by the nonideal grid conditions. Specifically, the possible wide variation of the grid impedance challenges the system stability. Meanwhile, background harmonics of the grid can greatly distort the injected current. Therefore, the control of the inverter should be designed with strong stability-robustness and high harmonic-rejection-ability, both of which correlate closely with the inverter output impedance. However, it is difficult to shape the output impedance into the one with a desirable characteristic simply by adjusting the current loop gain. In this paper, an impedance shaping method is proposed with virtual impedances, and the current control loop can be designed independently. The implementation and parameter design of the virtual impedances are studied under the practical considerations. With this proposed method, the grid-connected inverter can work stably over a wide range of the typical inductive-resistive grid impedance and exhibit strong rejection ability of grid-voltage harmonics. Experimental results from a 6-kW single-phase grid-connected inverter confirm the effectiveness of the proposed method.
378 citations
TL;DR: In this article, the authors construct a model of ac impedance response to blocked linear diffusion that has a sloped low frequency region in the impedance plot, which is equivalent to solving Fick's law with a boundary condition that allows us to set an arbitrary impedance response at low frequencies.
377 citations
IBM1
TL;DR: In this paper, an integral-equation (IE) computer-solution technique is presented to calculate capacitances for three-dimensional conductors located on parallel planes, which minimizes computer storage requirements while maintaining calculating efficiency computation times.
Abstract: The design and packaging of integrated circuits requires the calculation of capacitances for three-dimensional conductors located on parallel planes. An integral-equation (IE) computer-solution technique is presented, which provides accurate results. The solution technique minimizes computer storage requirements while maintaining calculating efficiency computation times.
377 citations
TL;DR: The impedance of skin coated with gel but otherwise unprepared was measured at ten sites on the thorax, leg, and forehead of ten subjects, which suggests that the variation in skin impedance can cause errors in two-electrode electrical impedance tomographs.
Abstract: The impedance of skin coated with gel but otherwise unprepared was measured from 1 Hz to 1 MHz at ten sites on the thorax, leg, and forehead of ten subjects. For a 1-cm/sup 2/ area, the 1 Hz impedance varied from 10 k Omega to 1 M Omega , which suggests that the bipotential amplifier input impedance should be very high to avoid common-mode-to-differential-mode voltage conversion. The 1-MHz impedance was tightly clustered about 120 Omega . The 100-kHz impedance was about 220 Omega , which suggests that the variation in skin impedance can cause errors in two-electrode electrical impedance tomographs. >
364 citations