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1.
Input characteristics of variable modulation index controlled current source inverters 总被引:1,自引:0,他引:1
Moschopoulos G. Joos G. Ziogas P.D. 《Industrial Electronics, IEEE Transactions on》1994,41(2):216-223
Standard PWM current source inverters (CSIs) usually operate at fixed modulation index. The proposed modified current source inverter (MCSI) can operate with most pulse width modulation (PWM) techniques and with a variable modulation index, since the DC link inductor current freewheels on itself and not through the CSI. The use of variable modulation index control results in faster response times with no penalty on input power factor as compared to other variable modulation index schemes. This paper confirms this by investigating the input characteristics of the MCSI as seen from the AC mains. The quality of the input AC line currents is examined, and a design procedure for the input filters is given. Power factor and efficiency are discussed. Results are compared to those of other current source inverter topologies. Experimental results obtained from a 5 kVA converter confirm the theoretical considerations.<> 相似文献
2.
Benchmarking Least Squares Support Vector Machine Classifiers 总被引:16,自引:0,他引:16
van Gestel Tony Suykens Johan A.K. Baesens Bart Viaene Stijn Vanthienen Jan Dedene Guido de Moor Bart Vandewalle Joos 《Machine Learning》2004,54(1):5-32
In Support Vector Machines (SVMs), the solution of the classification problem is characterized by a (convex) quadratic programming (QP) problem. In a modified version of SVMs, called Least Squares SVM classifiers (LS-SVMs), a least squares cost function is proposed so as to obtain a linear set of equations in the dual space. While the SVM classifier has a large margin interpretation, the LS-SVM formulation is related in this paper to a ridge regression approach for classification with binary targets and to Fisher's linear discriminant analysis in the feature space. Multiclass categorization problems are represented by a set of binary classifiers using different output coding schemes. While regularization is used to control the effective number of parameters of the LS-SVM classifier, the sparseness property of SVMs is lost due to the choice of the 2-norm. Sparseness can be imposed in a second stage by gradually pruning the support value spectrum and optimizing the hyperparameters during the sparse approximation procedure. In this paper, twenty public domain benchmark datasets are used to evaluate the test set performance of LS-SVM classifiers with linear, polynomial and radial basis function (RBF) kernels. Both the SVM and LS-SVM classifier with RBF kernel in combination with standard cross-validation procedures for hyperparameter selection achieve comparable test set performances. These SVM and LS-SVM performances are consistently very good when compared to a variety of methods described in the literature including decision tree based algorithms, statistical algorithms and instance based learning methods. We show on ten UCI datasets that the LS-SVM sparse approximation procedure can be successfully applied. 相似文献
3.
4.
A novel three-phase solid-state power factor compensation scheme is presented and analyzed. This scheme employs a PWM voltage-source inverter and has two important features. First, it can maintain a near-unity mains input power factor without sensing and computing the associated reactive power component, and second, it can substantially reduce any line current harmonics generated by nonlinear types of load. The proposed scheme is discussed in terms of principles of operation, power system design, and analysis under unbalanced operating conditions. Predicted results are verified experimentally 相似文献
5.
Luc Claesen Joos Vandewalle Hugo de Man 《International Journal of Circuit Theory and Applications》1983,11(3):241-264
In this paper we describe how three simple observations can be used in order to obtain an efficient algorithm for the computer analysis of ideal switched-capacitor circuits. the resulting algorithm is linear in the number of phases. the first observation uses the structure of the r-domain MNA-matrix to come up with a new LU-decomposition scheme which is gradual per timeslot. the second observation allows a great reduction in size of the z-domain MNA-matrix by a matrix compaction algorithm which also operates gradually per timeslot and which can be interleaved with the first gradual LU-decomposition process. This leads to a small matrix which can then be used for a time- and direct frequency-domain analysis. Third, the computations of transfer functions, aliasing functions and sensitivities can be optimized by applying appropriate excitations and making appropriate combinations of the terms in the expressions. These algorithms have been implemented in the SC-analysis program DIANA.SC. the usefulness and efficiency of the program is then illustrated with some examples. 相似文献
6.
A new adaptive scheme for continuous-time model reference adaptive control systems is proposed. It is shown that this scheme allows us to increase the exponential rate of parameter convergence to an arbitrary, desired level subject to a sufficiently rich reference input and a sufficiently large adaptive gain, while retaining global stability of the overall system. For simplicity and brevity the results are presented for plants with known high-frequency gain kp . 相似文献
7.
The purpose of this research is to deliver free-electron-laser (FEL) pulses for intraocular microsurgery. The FEL at Vanderbilt University is tunable from 1.8 to 10.8 mum. To deliver the FEL beam we used a metallic-coated hollow-glass waveguide of 530-mum inner diameter. A 20-gauge cannula with a miniature CaF(2) window shielded the waveguide from water. Open-sky retinotomy was performed on cadaver eyes. The system delivered as much as 6 x 10(5) W of FEL peak power to the intraocular tissues without damage to the waveguide or to the surgical probe. 相似文献
8.
Joos F. Miguel Snaddon Robert W. L. Johnson Neil A. 《Industry Applications, IEEE Transactions on》1985,(6):1366-1372
Droplet growth is examined in a water-in-oil type emulsion where the droplets are subjected exclusively to viscous and dielectrophoretic forces. The latter are produced by the interaction of the droplets with an otherwise uniformly imposed electric field. Theoretical considerations are presented as a basis for understanding and interpreting the experiments. An emulsion consisting of deionized water droplets in a silicone oil of specific gravity I is subjected to a uniform 60 Hz, ac electrostatic field. Initially, the droplets are fairly monodisperse with mean diameters of approximately 25 , sm. The changes in droplet size distributions with time are examined with a laser diffraction system for water volume fractions ranging from 0.001 to 0.1 and applied fields ranging from 52 to 520 kVm-1. The average droplet size increases exponentially with time; we examine the exponent's dependence on average field strength and droplet volume fraction. 相似文献
9.
A zero voltage transition boost converter employing a soft switching auxiliary circuit with reduced conduction losses 总被引:7,自引:0,他引:7
This paper presents a zero-voltage-transition (ZVT) boost converter using a soft switching auxiliary circuit for power factor correction (PFC) applications. The improvement over existing topologies lies in the positioning of the auxiliary circuit capacitors and the subsequent reduction in the resonant current and therefore the conduction losses as compared to other similar topologies. The proposed converter operates in two modes - Mode 1 and Mode 2. It is shown in the paper that the converter should be designed using the constraints obtained in Mode 1 to achieve low-loss switching. The converter is analyzed and characteristic curves presented which are then used in a detailed design example. Experimental results from a 250 W, 127 V input laboratory prototype switching at 100 kHz verify the design process and highlight the advantages of the proposed topology. The proposed converter is suitable for single-phase, two stage power factor correction circuits with universal input voltage range and power levels up to 3 kW. 相似文献
10.
This paper presents a generalized approach for the estimation of average displaced or avoided system emissions by intermittent renewable sources such as wind. The quantification of the environmental benefits of renewable energy projects is of utmost importance for: 1) the creation and trading of certified emission reductions or credits and 2) the design of green energy government policies that recognize the contribution of renewable energy for the reduction of national/regional carbon emissions. The proposed approach is based on the correlation factor between time-evolution of system marginal emissions and wind power generation. Results show that average displaced emissions by wind generation can be estimated once typical power system dispatch data and regional wind generation is available, thus circumventing the use of proprietary power dispatch models. The main objective of this work is to contribute towards the development of simplified methodologies that will facilitate the assessment of renewable energy projects in a variety of regulatory and regional settings. 相似文献