Coupled-wave small-signal transient analysis of GaAs distributedamplifier

The analysis takes into consideration the effect of c_dg in the active device, leading to a coupled-mode formulation. Dispersions within the transmission lines and the presence of two normal modes make it impractical to obtain broadband matching. Numerical results for specific terminations and various degrees of passive and active coupling clearly indicate the influence of c _dg and the necessity for coupled-mode analysis. The numerical scheme, which is based on Bromwich integration, can be incorporated into CAD routines for time-domain response optimization     

Recent trends and progress in synchronous machine modeling in the electric utility industry

Models of synchronous machines which have been developed and used to analyze problems in the electric utility industry are described. The development of alternative models, the transitions among the models, and the relations between problem and model are demonstrated. Lower order models using standardized data are used in multigenerator stability studies. Machine and system tests and the computer results of simulating these tests are reviewed. The areas of agreement and differences between simulation and test for alternate models point to ways in which improvements may be made in the economy and accuracy of computer simulations. This leads to suggestions for future work and a discussion of an IEEE Working Group in this field.     

Three-step impedance criterion for small-signal stability analysis in two-stage DC distributed power systems

Small-signal stability analysis methods based on an impedance criterion originate from the minor loop gain method and are gradually utilized in two-stage DC distributed power systems. In this paper, we conclude that the impedance criterion directly dependent on output impedance Z/sub o/(s) of the source subsystem and input impedance Z/sub i/(s) of the load subsystem is possible but gives an incorrect stability analysis for systems with a regulated source subsystem. Through introducing a mapped pure impedance of the load subsystems and the preliminary system, we develop a general three-step impedance criterion, with which a correct small-signal stability analysis can be guaranteed, regardless of the type of source subsystem. Furthermore, we introduce the application of the three-step impedance criterion in two small-signal stability analysis cases and utilize it in an example system to predict the stability shift process arising from the variation on the load resistance and input voltage value.     

Normal-mode small-signal analysis of traveling-wave directionalcouplers

The small-signal frequency responses of the 1×2 and 2×2 directional coupler traveling-wave modulators are analyzed in closed forms including the effect of both the optical/microwave velocity mismatch and microwave loss. When the microwave loss is negligible, the small-signal bandwidths of 1×2 and 2×2 directional coupler traveling-wave modulators are 20 and 28%, respectively, larger than that of an interferometric modulator with the same electrode length. However, when the microwave loss is large, the 1×2 coupler has a larger bandwidth     

Non-quasi-static transient and small-signal two-dimensionalmodeling of GaAs MESFET's with emphasis on distributed effects

The operation of micron and submicron GaAs MESFETs under high-speed transient and high-frequency small-signal conditions is analyzed using a two-dimensional model. The effects of displacement currents, dipole due to negative differential mobility or current continuity, and two-dimensional transport are emphasized. The origin of delay effects, such as the phase delay incorporated in small-signal models, is explored in order to relate it to the behavior under switching conditions. Broadband expressions for the extraction of a complete small-signal model are presented. Using the expressions derived, the variation of model elements with frequency and the effect of this on the unilateral gain of the device are studied     

Determination of generation lifetime from the small-signal transient behavior of MOS capacitors

The theory and an experimental proof of a method for determining generation-lifetime in silicon with impurity concentrations up to 10¹⁸ cm^?3 are described. Generation-lifetime is obtained by analyzing the transient behavior of the total charge stored in a MOS-capacitor after a very small depleting voltage step. The analytical expression allowing this analysis is deduced from the Shockley-Read-Hall-expression of the carrier generation rate by considering small deviations from thermal equilibrium. The small signal expression thus obtained differs in a constant factor only from the well known large signal expression. A comparison of this small-signal method with well known large signal methods practiced on samples with doping levels of 10¹⁵ cm^?3 shows that the results are in very good agreement.     

Generalized small-signal analysis of avalanche transit-time diodes

The one-dimensional small-signal analysis of avalanche transit-time diodes with distributed multiplication is reduced to the concept of two layers in cascade, each having a constant ionization rate. The interface is located in the distinguished neutral plane of equal direct electron and hole currents. In this configuration the small-signal problem is characterized by two parameters : namely the location of the neutral plane in the depletion layer and a quantity combining the ionization-rate field dependence and the total direct current density. Normalized admittance diagrams and small-signal growth rates are given which show the relative importance of the low-transit-angle mode where the frequency is smaller than the avalanche resonance frequency and the π mode extending almost to 2π for large current densities. Through a transformation the results are applicable to Read type, abrupt and uniform junctions of Si, Ge, and GaAs avalanche diodes.     

Techniques for small-signal analysis of semiconductor devices

Techniques for ascertaining the small-signal behavior of semiconductor devices in the context of numerical device simulation are discussed. Three standard approaches to this problem will be compared: (i) transient excitation followed by Fourier decomposition, (ii) incremental charge partitioning, and (iii) sinusoidal steady-state analysis. Sinusoidal steady-state analysis is shown to be the superior approach by providing accurate, rigorously correct results with reasonable computational cost and programming commitment.     

Corporate model of an electric utility

The importance of computers and simulation in management planning is reflected in this article describing a model of a hypothetical, investor-owned electric utility company. The model, which consists of three interrelated digital computer programs?an economic simulation, a cost simulation (based on power generation expenses), and an auxiliary nuclear fuel management program?is designed as a total corporate planning tool. All corporate activities, and certain environmental parameters, are represented by the economic simulation. The production cost simulation is designed to supply fuel cost information to the economic simulation and the fuel management program to supply nuclear fuel scheduling and cost data to both of the other programs. In the corporate model, management?both financial and operative?has a tool by which it is able to quickly assess the effects of one department's action upon another.     

Modeling and small-signal analysis of controlled on-time boostpower-factor-correction circuit

A large-signal average model for the controlled on-time boost power-factor-correction (PFC) circuit is developed and subsequently linearized, resulting in a small-signal model for the PFC circuit. AC analyses are performed using the small-signal model, revealing new results on the small-signal dynamics of the PFC circuit. The analysis results and model predictions are confirmed with experimental measurements on a 200-W prototype PFC circuit     

Integration of equation- and signal-based models in transient analysis of electric energy systems

The paper addresses analytical and practical aspects of integration of equation-based (classical) and signal-derived [artificial neural network (ANN)] dynamic models for transient analysis of large-scale dynamical systems. Our signal-based part is based on two ANNs, and is derived from measurements at boundary points. In this paper, we describe this hybrid modeling technique, and focus on: 1) a least square-based mechanism for on-line correction of dynamic variable predictions that is based on actual operating conditions; 2) the resilience of the algorithm to missing measurements due to failed communication links; and 3) a complete two-way interaction between the differential-algebraic equation based subsystem and the ANN-based subsystem. The paper demonstrates the feasibility of implementing our approach in standard power system software by integrating the ANN-based model with the transient analysis toolbox from Matlab. We illustrate capabilities of the proposed approach for transient analysis on a benchmark multi-machine example derived from the New England/New-York interconnected power system.     

电力系统暂态稳定分析方法的现状与发展

随着电力系统的发展,互联电力网络变得越来越大,暂态稳定性问题日趋严重,而电力系统安全运行的关键之一是可靠的暂态稳定分析。通过介绍电力系统暂态稳定分析常用的几种方法,回顾电力系统暂态稳定的发展历史和现状,对比分析了几种方法的特点及适用范围,并在此基础上对电力系统暂态稳定分析的发展前景进行了展望。最后指出,小波分析用于电力系统暂态稳定分析具有广阔的发展空间,特别是在处理暂态信号方面,更是一个很有应用价值的研究方向。     

Approximate small-signal analysis of the series and the parallelresonant converters

Approximate transfer functions of series and parallel resonant converters are given which are in good agreement with the results of exact analysis as well as the results of experiments. It is shown that the dominant behavior of these transfer functions is determined by the output low-pass filter modified by the internal impedance of the converter. The high-frequency behavior, on the other hand, is given by a second-order response whose frequency is at the difference between the resonant and the switching frequencies and whose Q is the original resonant Q modified by the internal impedance of the converter     

An analysis of small-signal and large-signal base resistances forsubmicrometer BJT's

Small-signal and large-signal base resistances for submicrometer BJT's have been analyzed in detail by using a two-dimensional device simulator. It has been clarified that the small-signal base resistance cannot be obtained from the input impedance semicircle in the complex plane accurately due to the effect of the emitter resistance at low frequencies, and also due to the reduction of the base-emitter junction resistance and the diffusion capacitance at high frequencies. A new method for extracting an accurate value of the small-signal base resistance is proposed. The extracted small-signal base resistance not only differed from the large-signal base resistance extracted from the dc characteristics of a BJT, but also agreed with the differential resistance. It has been shown that, for a 0.6 μm emitter-width BJT, the measured value of the small-signal base resistance is less than half that of the large-signal base resistance in the bias region in which actual BJT circuits operate     

A novel frequency-domain small-signal analysis of resonant power converters

A frequency-domain small-signal analysis of resonant power converters is presented. In this analysis, the load presented to the ac side of the rectifier is modeled as a time varying resistor. Using conversion matrix techniques and an iterative procedure to find the magnitude and phase of the time-varying resistor, the transfer functions of the converter can be obtained fast and accurately. An advantage of this approach is that the analysis can be carried out with the load represented in the frequency domain. This is a significant advantage when dealing with complex (e.g., plasma) loads where only measured small-signal impedance data may be available. An example demonstrating the accuracy of the method is presented.     

Large static converters for industry and utility applications

The emergence of high-power semiconductor devices such as insulated-gate bipolar transistors (IGBTs) or injection-enhanced gate transistors (IEGTs) and gate-commutated turn-off (GCT) thyristors or integrated gate-commutated thyristors (IGCTs) enables large static converters to expand into utility and industry applications. For instance, a ±80 kV 50 MW HVDC transmission system based on a string of many IGBTs connected in series was commissioned in 1999. This paper describes the present status of large static converters, with focus on their applications to utility and industry. The applications discussed are: HVDC transmission system, UPFC, flywheel energy storage system, pumped hydro plant adjustable speed generator, active filters for power conditioning, and steel mill drives. The paper also describes their future prospects and directions in the 21st century, including the personal views and expectations of the author     

Improved small-signal analysis of the quantum-well injectiontransit time diode

Two improved methods for calculating the small-signal impedance of the quantum-well injection transit time diode are discussed. The first extends the traditional analysis to include carrier velocity transient effects, producing an analytical expression from which optimum injection conductance and drift angle can be found. The second method includes the effects of both nonuniform carrier velocity and diffusion, casting the expression for impedance in terms of a double integration that is evaluated numerically. A lumped-element model that closely duplicates the impedance found by the numerical method is developed. A graphical means that allows the generation of the lumped-element model from the DC negative resistance and knowledge of the diode structure is provided. The more sophisticated models developed should be useful in device design, in evaluation of mounting and packaging schemes, and for suppression of unwanted oscillations     

Numerical analysis of nonlinear small-signal distortion in p-n structures

A numerical method is presented to derive the non-linear distortion of small ac signals in one-dimensional semiconducting diodes from the basic physical equations. The nonlinear input-output relations are obtained in terms of Volterra functional series. The application of this method is illustrated by computational results showing the influence of injection level on harmonic distortion and cross-modulation in p-i-n diodes. Computed values of cross-modulation are compared with measurements.     

Power system transient stability analysis: Formulation as nearly Hamiltonian systems

In this paper we formulate power systems as nonlinear nearly Hamiltonian systems. Using the invariance principle for ordinary differential equations, necessary and sufficient conditions for asymptotic stability are established and a new method of estimating the domain of attraction of the stable equilibrium point is developed. The present results constitute a novel approach to stability analysis and involve the following three steps:

1. Given a system with dissipation, the stability of its equilibrium is ascertained by determining the stability of the associated conservative system.
2. Attractivity of the stable equilibrium of the entire system (with dissipation) is determined from the system topology.
3. An estimate of the domain of attraction of the asymptotically stable equilibrium is obtained by making use of results obtained in (a) and (b).

The stability criterion developed in this paper sheds new light on the mechanism of instability in power systems and it provides analytical verification to the concept of the potential-energy boundary surface (PEBS). The PEBS is a hypersurface which makes up a part of the boundary of the domain of attraction of the stable equilibrium in a power system. The existence and properties of the PEBS have thus far been deduced primarily via simulations and heuristic methods.