Short-circuit Admittance Research Articles

Accelerated Electromagnetic Transient (EMT) Equivalent Model of Solid-State Transformer

Accurate and efficient electromagnetic transient (EMT) simulation of various types of solid-state transformers (SSTs) is extremely time-consuming due to the complex module structure, flexible topology connections, large number of electrical nodes, and simulation time steps limited in the range of microseconds. Therefore, it is urgent to develop the EMT equivalent modeling and fast simulation of SSTs for system-level studies. Taking the modular multilevel converter (MMC)-based SST as an example, this article proposes an accelerated EMT model, which focuses on the equivalence of the dual-active-bridge (DAB)-based high-frequency link (HFL) in the SST. Compared with the existing algorithms, two critical factors of the proposed method that contribute the most to the efficiency improvement are the preprocessing of the nodal admittance equation and the conversion of the short-circuit admittance parameters. The proposed model is verified in PSCAD/EMTDC by comparing it with the detailed EMT model. The results show that the accelerated model is one-to-two orders of magnitude faster than the detailed model without sacrificing accuracy. The experiment validation also confirms the validity of the proposed model.

Elicitation of Scattering Parameters of Dual-halo Dual-dielectric Triple-material Surrounding Gate (DH-DD-TM-SG) MOSFET for Microwave Frequency Applications

This paper presents an analytical model for intrinsic short-circuit admittance (Y) parameters of DH-DD-TM-SG MOSFET. Y parameters have been modeled using different small-signal equivalent circuit parameter which is used to find the Scattering parameters. These Y parameters have further been employed for computing S-parameters. These parameters are further used to investigate the microwave performance parameters of the proposed device. The Unilateral Power Gain and the maximum oscillation frequency is determined to evaluatethe microwave performance. The proposed device shows a higher cut-off frequency (f_T) and maximum oscillation frequency as to TM-SG MOSFET. The proposed device exhibits a 4.2% improvement in U_T 2.81% in G_ms and 6.9% improvement in G_MTPG as compared to TMSG. The analytical result of DH-DD-TM-SG MOSFET is in accordance with the simulated results.

Extraction of admittance parameters of symmetrically doped AlGaN/GaN/AlGaN DH-HEMT for microwave frequency applications

An analytical model for determining intrinsic short-circuit admittance (Y) parameters of AlGaN/GaN/AlGaN Double Heterostructure (DH) High Electron Mobility Transistor (HEMT) is presented. These Y parameters obtained in terms of the various small signal equivalent circuit parameters are in turn used to evaluate the enhanced microwave performance of the DH-HEMT in terms of various parameters including Unilateral Power Gain and maximum oscillation frequency. The cut-off frequency has been evaluated from short circuit current gain. The cut-off frequency (fT) and maximum oscillation frequency (fmax) exhibited for DH-HEMT is 125 GHz and 215 GHz which is comparatively improved as obtained in Single Heterostructure (SH) HEMT (fT = 105 GHz and fmax = 165 GHz). The analytical results obtained for DH and SH-HEMT; have been compared and found to match well with the ATLAS 2D device simulation results thus proving the validity of the model.

Modeling and analysis of ultrasonic power transfer system with tightly coupled solid medium

Ultrasonic Power Transfer (UPT) has been developed as an alternative solution for achieving wireless power transfer. This paper proposes a new model describing UPT systems with tightly coupled piezoelectric transducers firmly bound to solid media. The model is derived from the short-circuit admittance of the system measured from the primary transducer. The mechanical characteristics of the system are modeled with parallel LCR branches, which reveal the fundamental relationships between the power transfer characteristics of the tightly coupled UPT system and system parameters. The loading conditions for achieving the maximum power transfer are identified, and the operating frequencies corresponding to the peak power transfer points for variable loads are determined. A practical UPT system is built with two 28 kHz Langevin-type piezoelectric transducers connected to a 5 mm-thick aluminum plate, and the practical results have verified the accuracy of the proposed model.

RF characterization of 100‐nm separate gate InAlAs/InGaAs DG‐HEMT

ABSTRACTThis article presents a three port analysis for separate gate In0.52Al0.48As/In0.53Ga0.47As DG‐HEMT and a small signal equivalent circuit is developed using charge control model. The various intrinsic short circuit admittance parameters (Y‐parameters) are evaluated to extract scattering parameters, to determine the maximum transducer power gain of the device. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2796–2803, 2013

A Hybrid Measurement Approach for Wideband Characterization and Modeling of Power Transformers

This paper describes a hybrid procedure for wideband characterization and modeling of power transformer behavior from frequency sweep measurements. The approach is based on measuring corresponding sets of voltage and current vectors that are associated with short circuit and open circuit conditions. These vectors are stacked side-by-side in two matrices which are used for computing the short circuit admittance matrix. This hybrid approach is shown to give more information about the transformer behavior than the traditional approach of measuring the admittance matrix directly under short-circuit conditions, which tends to corrupt the small eigenvalues associated with open-circuit conditions. From the obtained admittance matrix, a pole-residue model is extracted via vector fitting and passivity enforcement, thereby giving a model ready for EMTP simulation. The accuracy of the small eigenvalues is retained by using a modal formulation in the fitting and passivity enforcement step. Application to a distribution transformer shows that the hybrid approach can greatly improve the accuracy of time-domain simulations involving high-impedance terminations.

Distribution transformers modeling with angular displacement: actual values and per unit analysis

In this work a detailed modeling of three-phase distribution transformers aimed at complementing well-known approaches is presented. Thus, incidence of angular displacement and tapping is taken into account in the proposed models, considering both actual values and per unit. The analysis is based on minimal data requirement: solely short-circuit admittance is needed since three-phase transformers are treated as non-magnetically-coupled single-phase transformers. In order to support the proposed methodology, results obtained through laboratory tests are presented.

A Vector-Fitting Formulation for Parameter Extraction of Lossy Microwave Filters

In this letter, a formulation based on the vector fitting is applied to extract the equivalent circuit model from the frequency response of lossy cross-coupled microwave filters. By approximating the lossy response with short-circuit admittance parameters in partial fractional expansion form, the proposed method can evaluate the unloaded quality factor of resonators and extract the transversal coupling matrix simultaneously. The methodology of the vector fitting can identify the poles and residues of the short-circuit admittance parameters even when the poles are on the complex plane. And the extracted transversal coupling matrix can further transform into the prescribed form corresponding to the physical layout. The proposed method can be used in the tuning process of filter designs where the extraction of a coupling matrix is essential. To verify the method, a cross-coupled quadruplet filter is used as an example

Simplified model for estimation of lightning induced transient transfer through distribution transformer

In this work a simplified procedure for the formulation of distribution transformer model for studying its response to lightning caused transients is presented. Simplification is achieved by the way with which the model formulation is realised. That is, by consolidating various steps for model formulation that is based on terminal measurements of driving point and transfer short circuit admittance parameters. Sequence of steps in the model formulation procedure begins with the determination of nodal admittance matrix of the transformer by network analyser measurements at the transformer terminals. Thereafter, the elements of nodal admittance matrix are simultaneously approximated in the form of rational functions consisting of real as well as complex conjugate poles and zeros, for realisation of admittance functions in the form of RLCG networks. Finally, the equivalent terminal model of the transformer is created as a π-network consisting of the above RLCG networks for each of its branches. The model can be used in electromagnetic transient or circuit simulation programs in either time or frequency domain for estimating the transfer of common mode transients, such as that caused by lightning, across distribution class transformer. The validity of the model is verified by comparing the model predictions with experimentally measured outputs for different types of common-mode surge waveform as inputs, including a chopped waveform that simulate the operation of surge arresters. Besides it has been verified that the directly measured admittance functions by the network analyser closely matches the derived admittance functions from the time domain impulse measurements up to 3 MHz, higher than achieved in previous models, which improves the resulting model capability of simulating fast transients. The model can be used in power quality studies, to estimate the transient voltages appearing at the low voltage customer installation due to the induced lightning surges on the high voltage side of the transformer. The procedure is general enough to be adapted for any two-port devices that behaves linearly in the frequency range of interest.

Improved method to extract the short-circuit parameters of the BECM

The current method for extracting the short-circuit broadband extended cantilever model (BECM) parameters requires measurement of short-circuit currents, and is problematic over a wide frequency range, prohibiting each short-circuit parameter to be directly measured. The improved method presented herein eliminates the measurements of short-circuit currents. Each short-circuit BECM parameter is directly found from two measurements, an open-circuit voltage gain and a short-circuit admittance. The method is demonstrated for a published five-winding BECM.

Efficient Modeling of Periodic Structures

An extended algorithm for the analysis of periodic structures is proposed and substantiated. The algorithm is based on the open-circuit impedance (short-circuit admittance) matrix-parameter description of two ports. With these parameters the characteristic values of Floquet modes are determined. Furthermore, impedance/admittance transformation formulas are developed for N concatenated period sections. The proposed algorithm is verified by numerical results.

Fault detection for linear analog IC-the method of short-circuit admittance parameters

A fault detection method, i.e. the short-circuit admittance parameters method, for linear analog ICs is proposed in this paper. Only two voltage measurements at the ports of the circuit are suggested to decide whether the circuit is working normally. This method can be used to design automatic circuit fault detection equipment for technicians to decide whether there are any faults in linear analog circuits. The attractive merits of this method are component parameter tolerance and error reduction in measurement and calculation.

Parametric identification of two-port models in the frequency domain

The authors treat the problem of parametric estimation of linear time-invariant dynamic two-port models (e.g. the short-circuit admittance matrix) from experimental data. A multivariate frequency-domain Gaussian maximum likelihood estimator is proposed to estimate the unknown coefficients occurring in the rational two-port model. It takes the perturbing noise of all the measured voltages and currents into account. The covariance matrix of the noise is assumed to be known, e.g. from measurements. The estimates and their covariance matrix are obtained as the result of an optimization procedure. The value of the minimized loss function and the covariance matrix of the estimates can be used to determine the model structure. The ability of the estimator to handle real measurement problems is demonstrated by means of experimental results. Using the estimated two-part parameters of an unloaded band-pass filter, it was possible to predict the transfer function of the loaded filter within an error of +or-0.01 dB on the magnitude and +or-0.1 degrees on the phase.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Technical memorandum: Analysis of curtain arrays for HF broadcasting

A method of analysing HF dipole curtain arrays is presented which uses a circuit model to compute the currents fed to the dipole elements. A standard moment-method analysis is carried out once to establish the short-circuit admittance matrix for the set of dipoles. Subsequently the circuit-model analysis can be used to compute the performance of the array with alternative feeder configurations very quickly. Mutual coupling within the array is taken fully into account. Measured results are presented in confirmation.

Exact sensitivities for nonreciprocal two-port power elements

A novel method is presented to calculate exact first-order sensitivity formulas for nonreciprocal two-port power elements using the short-circuit admittance description. The method exploits an augmented Tellegen's theorem and is applied to an elegant adjoint transformer model to evaluate sensitivities with respect to control parameters of phase-shifting transformers.

Further non-series-parallel 3-terminal RC networks having no parallel equivalent

By the construction of an appropriate numerical example, Fialkow demonstrated the existence of a non-series-parallel 3-terminal RC network for which a series-parallel equivalent was intrinsically impossible. Starting from the set of short-circuit admittance functionscorresponding to this network and using computer synthesis methods, the authors obtained a number of realizations, or possibly near-realizations, for this set of functions. In view of the theoretical interest involved, it was decided to check whether any of these realizations did, in fact, correspond to exact solutions of the synthesis problem; a number of such exact solutions were found and are exhibited in this paper together with other sets of short-circuit admittance functions that can only be realized as 3-terminal RC networks in non-series-parallel form.

A two-dimensional model for the lateral p—n—p transistor

A two-dimensional solution of the continuity equation in the base of the lateral p-n-p transistor, including interactions with the substrate and subdiffused layer, is presented for dc excitation. This method is extended to the case of steady-state sinusoidal excitation. Computed and measured results are presented for the frequency dependence of the Short-circuit small-signal current transfer ratios, and comparison of these shows reasonable agreement over the full range of measurements. An approximate equivalent circuit derived from a single-pole fit to the frequency response of short-circuit admittance parameters is inferred to be valid Up to a few megahertz for the device considered.

A Theoretical Study of the High-Frequency Performance of a Schottky-Barrier Field-Effect Transistor Fabricated on a High-Resistivity Substrate

The short-circuit admittance parameters for a silicon Schottky-barrier field-effect transistor (SBFET) fabricated on a high-resistivity substrate are calculated from first principles ignoring the effects of minority carriers. The calculations show the maximum frequency of oscillation for a device with a 1-/spl mu/m gate to be 17.9 GHz, neglecting the parasitic associated with the contact metallizations, and 14.7 GHz when the parasitic are included. In order to describe the dynamic behavior of the device, the static properties must first be obtained. The simultaneous solution of Poisson's equation and the continuity equation, both in two dimensions, gives the static charge and potential distribution in the device. The effects of a field-dependent mobility are included in the continuity equation. Using the results of static two-dimensional solutions, a one-dimensional device model is developed that permits the dynamic device behavior to be described by a one-dimensional linear ordinary differential equation. By solving this equation under appropriate boundary conditions, the device y parameters are found as functions of frequency. Calculated results are shown to be in good agreement with published experimental data.

HighQInductance Realization from a Cascade Transistor Amplifier

In this paper a reactance transistor circuit which can realize low Q inductance is analysed and procedure outlined to realize a given inductance with maximum Q. This reactance transistor when cascaded with another transistor in common collector configuration can realize a high, even infinite, Q inductance. A design procedure in terms of short circuit admittance parameters of transistors is outlined and an illustrative example worked out for the realization of infinite Q inductance from the cascade transistor arrangement.

Necessary and sufficient conditions for compactness of reciprocal RC two-port networks

Necessary and sufficient conditions are given for the compactness of the open-circuit impedance (or short-circuit admittance) matrix of a passive reciprocal RC two-port network when the specified short-circuit admittance (or open-circuit impedance) matrix of the network is compact. The conditions are applicable to unsymmetrical as well as to symmetrical reciprocal RC two-ports.