Capacitance Estimation Research Articles

넓은 범위의 선형 출력 제어를 위한 5kW 플라즈마 전원장치 설계 및 반응기 커패시턴스 추정 알고리즘의 관한 연구

넓은 범위의 선형 출력 제어를 위한 5kW 플라즈마 전원장치 설계 및 반응기 커패시턴스 추정 알고리즘의 관한 연구

Full range analog Wheatstone bridge‐based automatic circuit for differential capacitance sensor evaluation

SummaryIn this paper, an integrable novel fully analog Wheatstone bridge‐based interface for differential capacitance estimation is presented. Its working principle takes advantage of the modified De‐Sauty AC bridge configuration being employed only by two capacitors and two resistors. A feedback loop controls one of the resistors (e.g. a voltage‐controlled resistor), to obtain an evaluation of the differential capacitance variation on a full range, thanks to a general but very simple formula that considers both the ‘auto‐balancing’ and the bridge ‘out‐of‐equilibrium’ ranges. The proposed interface shows a satisfactory accuracy, being the percentage relative error within 0.45% for the experimental results. Copyright © 2016 John Wiley & Sons, Ltd.

Capacitance Estimation of the Submodule Capacitors in Modular Multilevel Converters for HVDC Applications

To achieve higher reliability in the modular multilevel converters (MMC) for HVDC transmission systems, the internal condition of the DC capacitors of the submodules (SM) needs to be monitored regularly. For an online estimation of the SM capacitance, a controlled AC current with double the fundamental frequency is injected into the circulating current loop of the MMC, which results in current and voltage ripples in the SM capacitors. The capacitor currents are calculated from the arm currents and their switching states. By processing these AC voltage and current components with digital filters, their capacitances are estimated by a recursive least square (RLS) algorithm. The validity of the proposed scheme has been verified by simulation results for a 300-㎿, 300-㎸ HVDC system. In addition, its feasibility has been verified by experimental results obtained with a reduced-scale prototype. It has been shown that the estimation errors for both the simulation and experimental tests are 1.32% at maximum.

Recursive-Least-Squares-Based Real-Time Estimation of Supercapacitor Parameters

The letter suggests utilizing a recursive-least-squares identification algorithm for real-time estimation of supercapacitor equivalent capacitance and resistance. Estimation is required since both parameters are subject to age, temperature, and terminal-voltage-based variations in addition to typical 20% tolerance of manufacturer provided values. The proposed approach allows calculating the device instantaneous state of energy used as a fuel gauge instead of the commonly adopted state of charge. Experimental results are given to verify the feasibility of the proposed method.

Gate engineered performance of single molecular transistor

The operation, performance and electrostatics of multigated Single Molecular Transistor (SMT) devices are investigated using first-principles based density functional theory calculations for planar (pentacene) and non-planar (sucrose) molecules as islands. It has been found that the incorporation of larger numbers of gates allows enhanced electrostatic control in the SMT operation which has been quantified from the energy calculations and estimation of the gate capacitances. The effect of multiple gates is more dominant for a non-planar molecule than a planar molecule within an SMT which indicates the usefulness of such multi-gate architectures for future nanoelectronic devices.

Capacitance Estimation Method of DC-Link Capacitors for BLDC Motor Drive Systems

This paper proposes a capacitance estimation method of the dc-link capacitor for brushless DC motor (BLDCM) drive systems. In order to estimate the dc-link capacitance, the BLDCM is operated in quadrant-II or -IV among four-quadrant operation. Quadrant-II and -IV are called reverse braking and forward braking, respectively. During the braking operation of the BLDCM, the capacitor is charged by the phase current and then the voltage is increased during the braking operation time. The capacitor current and voltage can be obtained by using the phase current sensor of BLDCM and the dc-link voltage sensor. The capacitance and be easily obtained by the voltage equation of the capacitor. The proposed method guarantees the reliable and simple calculation of the dc-link capacitance without additional hardware system except several the sensors already installed for the motor control system. The effectiveness of the proposed method is verified through both the simulation and experimental results.

A Fast Method for the Computation of the Capacitance of the Geometrically Symmetric Dielectric Coated Metallic Bodies Isolated in the Free Space

ABSTRACTThe method of moments based electrostatic modelling in the form of the capacitance estimation of the dielectric coated isolated metallic structure with finite size requires matrix inversion. The inversion of a large sized matrix consumes most of the simulation time apart from filling the sub-matrices related to the distance vector. The analysis of the literature reveals the symmetric nature of the charge density for the geometrically symmetric structures. This property is exploited to form a matrix of the reduced size in the paper. The pulse basis function and the point matching are used to form the set of simultaneous equations, resulting into a matrix equation. The matrix inversion is carried out to solve the matrix equation for the unknown charge density for the reduced sized matrix. The moment method analysis is coupled with the symmetry property of the charge density to achieve the faster convergence to compute the capacitance. The results of the capacitance obtained using the method presented are compared with the results computed with the method published in the literature.

Automatic Bridge-based Interface for Differential Capacitive Full Sensing

The authors here propose, for the first time, an automatic analog interface for differential capacitance estimation, able to reveal and quantify both low and high (full-range) capacitive variations. The working principle is based on a modified De-Sauty AC bridge configuration where two differential capacitances and two resistances are employed, one of which is implemented by a Voltage Controlled Resistor (VCR). Through a suitable feedback loop, a very accurate estimation over the complete range of the differential capacitance variation is possible, while the bridge allows a continuous differential capacitance evaluation without the need of knowing the accurate value of the sensor baseline and/or its variation range. A general but very simple formula, considering both the “autobalancing” and the “out-of-equilibrium” ranges, is also given. Theoretical, experimental and simulated results are in a very good agreement. Sensitivity and resolution values, typical of sensors and their interfaces, have been determined in a practical case, showing satisfactory values.

Artificial Neural Network Algorithm for Condition Monitoring of DC-link Capacitors Based on Capacitance Estimation

In power electronic converters, reliability of DC-link capacitors is one of the critical issues. The estimation of their health status as an application of condition monitoring have been an attractive subject for industrial field and hence for the academic research filed as well. More reliable solutions are required to be adopted by the industry applications in which usage of extra hardware, increased cost, and low estimation accuracy are the main challenges. Therefore, development of new condition monitoring methods based on software solutions could be the new era that covers the aforementioned challenges. A capacitance estimation method based on Artificial Neural Network (ANN) algorithm is therefore proposed in this paper. The implemented ANN estimated the capacitance of the DC-link capacitor in a back-toback converter. Analysis of the error of the capacitance estimation is also given. The presented method enables a pure software based approach with high parameter estimation accuracy.

Uncalibrated operational amplifier‐based sensor interface for capacitive/resistive sensor applications

In this paper, a new configuration of operational amplifier -based square-wave oscillator is proposed. The circuit performs an impedance-to-period (Z–T) conversion that, instead of a voltage integration typically performed by other solutions presented in the literature, is based on a voltage differentiation. This solution is suitable as first analogue uncalibrated front-end for capacitive and resistive (e.g. relative humidity and gas) sensors, working also, in the case of capacitive devices, for wide variation ranges (up to six capacitive variation decades). Moreover, through the setting of passive components, its sensitivity can be easily regulated. Experimental measurements, conducted on a prototype printed circuit board, with sample passive components and using the commercial capacitive humidity sensor Honeywell HCH-1000, have shown good linearity and accuracy in the estimation of capacitances, having a baseline or reaching a value ranging in a wide interval [picofarads–microfarads], as well as, with a lower accuracy, in the evaluation of more reduced variations of resistances, ranging from kiloohms to megaohms, also when compared with other solutions presented in the literature.

Deterioration Monitoring of DC-Link Capacitors in AC Machine Drives by Current Injection

This letter proposes a novel condition monitoring scheme of dc-link capacitors in PWM inverter-fed induction machine drives with front-end diode rectifiers, which is based on the online capacitance estimation scheme. While the motor is operating in the regenerative mode for the estimation process, a regulated ac component is injected into the stator winding, which causes a dc-link voltage ripple at the same frequency. From the ac components of the dc-link voltage and current, the capacitance is estimated with a recursive least squares algorithm. With this method, experimental results have shown that the estimation error of the capacitance is less than 1%, from which the deterioration condition of the capacitors can be diagnosed reliably.

Numerical methods and software tools for simulation, design, and resonant mode analysis of radio frequency birdcage coils used in MRI

ABSTRACTDesign of magnetic resonance imaging (MRI) radiofrequency (RF) coils using lumped circuit modeling based techniques begins to fail at high frequencies, and therefore more accurate models based on the electromagnetic field calculations must be used. Field calculations are also necessary to understand the interactions between the RF field and the subject inside the coil. Furthermore, observing the resonance behavior of the coil and the fields at the resonance frequencies have importance for design and analysis. In this study, finite element method (FEM) based methods have been proposed for accurate time‐harmonic electromagnetic simulations, estimation of the tuning capacitors on the rungs or end rings, and the resonant mode analysis of the birdcage coils. Capacitance estimation was achieved by maximizing the magnitude of the port impedance at the desired frequency while simultaneously minimizing the variance of RF magnetic field in the region of interest. In order for the proposed methods to be conveniently applicable, two software tools, resonant mode and frequency domain analyzer (RM‐FDA) and Optimum Capacitance Finder (OptiCF), were developed. Simulation results for the validation and verification of the software tools are provided for different cases including human head simulations. Additionally, two handmade birdcage coils (low‐pass and high‐pass) were built and resonance mode measurements were made. Results of the software tools are compared with the measurement results as well as with the results of the lumped circuit modeling based method. It has been shown that the proposed software tools can be used for accurate simulation and design of birdcage coils. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 45B: 13–32, 2015

Capacitance estimation for InAs Tunnel FETs by means of full-quantum [formula omitted] simulation

We report for the first time a quantum mechanical simulation study of gate capacitance components in aggressively scaled InAs Nanowire Tunnel Field-Effect Transistors. It will be shown that the gate-drain capacitance exhibits the same functional dependence over the whole Vgs range as the total gate capacitance, albeit with smaller values. However, as opposed to the previous capacitance estimations provided by semiclassical TCAD tools, we find that the gate capacitance exhibits a non-monotonic behavior vs. gate voltage, with plateaus and bumps related with energy quantization and subband formation determined by the device cross-sectional size, as well as with the position of channel-conduction subbands relative to the Fermi level in the drain contact. From this point of view, semiclassical TCAD tools seem to be inaccurate for capacitance estimation in aggressively-scaled TFET devices.

Estimation of load capacitance and stray inductance in lightning impulse voltage test circuits

In order to obtain the lightning impulse voltage waveshape regarding front time, time to half and relative overshoot magnitude within the limits prescribed by IEC 60060-1, it is useful to accurately estimate the test circuit parameters, e.g. load capacitance and circuit inductance. A stray inductance consists of the inductance of impulse generator and the inductance of connecting leads. Load capacitance consists of voltage divider capacitance, test object and parasitic capacitances. In practice, the test object capacitance is often unknown. Capacitance measurement takes time and makes testing procedure more complex. Also, it is very difficult to estimate parasitic capacitances although their influence can sometimes be significant.This paper presents a new genetic algorithm (GA) based method for fast and accurate estimation of load capacitance and circuit inductance during lightning impulse voltage testing of a capacitive load. Computational and experimental verification of the method is successfully performed for standard and non-standard lightning impulse waveforms with various relative overshoot magnitudes.

Novel Modified De-Sauty Autobalancing Bridge-Based Analog Interfaces for Wide-Range Capacitive Sensor Applications

In this paper, we propose novel fully analog uncalibrated readout circuits for wide-range capacitance estimation. The working principle is based on a modified De-Sauty ac bridge configuration where two capacitances and two resistances are employed. Through the use of a voltage controlled resistor and of a suitable feedback loop, an accurate estimation over a wide range of the sensor capacitance variation is possible, also without the knowledge of the other bridge component values. The first two proposed solutions are able to estimate, experimentally, ~1.5 decades (optimized range: [25-840 nF]) and more than 3 decades [900 pF-1.1 μF] of capacitive variations, respectively, ensuring, continuously, the bridge equilibrium condition; the third interface allows the evaluation of the sensor capacitance also outside this condition, increasing the capacitive variation decades to more than 4 [81 pF-1.1 μF]. The proposed topologies have been also modified to detect the capacitive sensor parasitic resistance. In this case, experimental results on PCB have demonstrated the capability to simultaneously estimate ~ 1.7 capacitive [2-100 nF] and 1.5 resistive variation decades [33 kΩ-1.2 MΩ]. Finally, a suitable optimization of the operating range of the first proposed solution, obtained through a proper passive components sizing, has been performed with the aim to employ the commercial humidity sensor HCH-1000 in a high accuracy (11.4 bits) RH% detection.

Correction to “Estimation of Series Capacitance of a Transformer Winding Based on Frequency-Response Data: An Indirect Measurement Approach” [Oct 11 2870-2878

A correction to the above title (ibid., vol. 26, no. 4, pp. 2870-2878, Oct. 2011) is presented.

Estimation of Free Space Capacitance and Body Potential of a Spacecraft for Charging Analysis

This paper presents a computation of the absolute free space capacitance and electrostatic body potential of a spacecraft using moment method with triangular patch modeling. Expressions are derived numerically and the moment integral is evaluated. The capacitance of a square plate is computed to validate the approach. Finally, the free space capacitance of a typical spacecraft is computed for various configurations and body potential is evaluated. The derived expressions are simple and suitable for developing the charging analysis tool. As this approach is more general, it can be easily applied to any practical spacecraft configuration.

Estimation of Series Capacitance for a Three-Phase Transformer Winding From Its Measured Frequency Response

Recently, authors published a method to indirectly measure series capacitance (Cs) of a single, isolated, uniformly wound transformer winding, from its measured frequency response. The next step was to implement it on an actual three-phase transformer. This task is not as straightforward as it might appear at first glance, since the measured frequency response on a three-phase transformer is influenced by nontested windings and their terminal connections, core, tank, etc. To extract the correct value of Cs from this composite frequency response, the formulation has to be reworked to first identify all significant influences and then include their effects. Initially, the modified method and experimental results on a three-phase transformer (4 MVA, 33 kV/433 V) are presented along with results on the winding considered in isolation (for cross validation). Later, the method is directly implemented on another three-phase unit (3.5 MVA, 13.8 kV/765 V) to show repeatability.

Fractal Electrode Formation in Metal–Insulator Composites Near the Percolation Threshold

Over the past 20 years, there have been a variety of experiments that have revealed a large increase in the low-frequency capacitance of devices constructed from metal-insulator nanocomposite materials. These capacitive increases are typically reported as dramatic increases in the effective relative dielectric constants of the nanocomposite materials. A class of these materials that operate at room temperature and have metal particle concentrations near the percolation threshold have been shown to have dramatic increases in the effective dielectric constant on the order of 104-1010. The simulations in this paper reveal that electrical contact to large metal clusters inside the composite material near the percolation threshold form fractal-like electrodes that deeply penetrate into the host dielectric material, which result in an effective dielectric constant that is 104-105 times greater than the host dielectric. Furthermore, insulating the planar electrodes so that no electrical contact is made to the metallic clusters inside a near-percolation-threshold composite material reveals a much smaller increase (40×) in the effective dielectric constant. Finally, a new physical scaling model and a simple geometric model for capacitance estimation in metal-insulator composites are developed and used to enhance understanding of the physical effects behind the results of these numerical simulations.

An Effective Capacitance Model for 28-nm and Beyond Copper Interconnect

In 28-nm CMOS technology, copper interconnect becomes complicated as the dielectric copper diffusion barrier and low-κ damage compromise capacitance gain from low-κ implementation. As a consequence, accurate and effective estimation of the interconnect capacitance is a very challenging task during integration and unit process development. This paper attempts to integrate the impacts of the technological innovations and presents a new compact capacitance model by modifying one of the existing empirical models. The new model demonstrates good agreement with Raphael simulation and less than 2% delta to the real Si data at 28-nm node. Effects of the transition layer and the low-κ damage layer on capacitance and the impact of terminal capacitance on the coupling capacitance are discussed in detail.