4,364 research outputs found
Modulating functions for modelling PWM switching converters
No full textThe aim of the work is to identify continuous average models of switching converters from input-output data. Among the various identification techniques, modulating functions were chosen due to their capability for revealing converter dynamics, even in the case of fast time constants. Due to its low-pass filtering property, such an identification technique reveals its effectiveness in the case of the evaluation of average models for switch-mode DC-DC converters. Following a brief description of the modulating functions properties, simulation and experimental examples of application are presented, first for the case of the basic boost converter and then for more complex topologies, like the half-bridge current doubler converter. The last example considers the application of such a technique to a resonant converter: a relevant result is that the technique allows an easy modelling particularly in critical cases of resonant converters where traditional averaging techniques fail
Modulating functions for testing the performance of switch-mode converters
No full textAim of the paper is to build mathematical models of DC-DC switch converters (Buck, Buck-Boost and Boost typologies) using input-output data. Among the various identification techniques, the choice of modulating function method was due to its low-pass filtering action. In plain words such feature appears a useful property for a suitable identification of average (low-pass) models at different operating points. The models proposed (including the effects of parasitic resistances) have been validated both by extensive simulations and by ex-perimental tests. An important outcome of such identification and modeling procedure is its effectiveness in performing an experimental evaluating of the loss parameters of the convert-ers: their determination is relevant for testing the efficiency of the switch-mode converte
An assessment of the impact of possible CAP reform scenarios on Romanian agriculture
No full textUsing a simplified model, with key-variable the prices of two different possible scenarios of CAP reform after 2013 (moderate and radical), this paper present a comparison between the price effects of implementation of each reform scenario at 2015 horizon on Romanian agriculture. This short analysis shows that, under the presented hypotheses, the net welfare effect, due to the price changes, for the selected products, is positive in both reform scenarios, yet greater in the case of the radical reform. Integrated in the large context of Romanian development, it seems that the influence of CAP reform upon agriculture and rural areas will be most likely a gradual one: an interpenetration between the two scenarios is foreseeable, starting with the moderate reform that will dominate the period around 2013, the reform measures acquiring a more radical character afterwards.CAP reform, Romania, welfare effects, Agricultural and Food Policy,
Rich, Sturmian, and trapezoidal words
No full textIn this paper we explore various interconnections between rich words, Sturmian words, and trapezoidal words. Rich words, first introduced by the second and third authors together with J. Justin and S. Widmer, constitute a new class of finite and infinite words characterized by having the maximal number of palindromic factors. Every finite Sturmian word is rich, but not conversely. Trapezoidal words were first introduced by the first author in studying the behavior of the subword complexity of finite Sturmian words. Unfortunately this property does not characterize finite Sturmian words. In this note we show that the only trapezoidal palindromes are Sturmian. More generally we show that Sturmian palindromes can be characterized either in terms of their subword complexity (the trapezoidal property) or in terms of their palindromic complexity. We also obtain a similar characterization of rich palindromes in terms of a relation between palindromic complexity and subword complexity
Closed Loop Tests for Performance Evaluations of Controlled DC-DC Switching Converters
No full textAn experimental performance-evaluation of controlled plants is a primary task for checking the validity of the controller design, especially in case of nonlinear plants, such as switching DC/DC converters. This paper presents a simple and automatic experimental method to estimate all circle based design specifications (gain and phase margin, sensitivity and closed-loop bandwidth). This procedure employs the Sinusoidal Auto Tune Variation (SATV) method to guarantee a high accuracy and robustness with respect to measurement noise. An application to a Boost converter is proposed
Large signal models of ZVS class E2 resonant converters
No full textThis paper proposes a simple and systematic procedure for identifying averaged large-signal models of resonant converters. The nonlinear behaviour of the converter is modelled via Hammerstein models, i.e., the model is represented by a static nonlinearity, followed by a linear transfer function. The parameters of the approximating structure are identified from input-output noisy data, with the application of modulating functions method. PSpice simulations and experimental tests are run for an exhaustive and accurate validation of the proposed methodology. A relevant result is that the technique allows an easy modelling in the critical case of resonant converters, where traditional averaging techniques fail
Procedure automatiche di autosintonia per modelli Hammerstein-Wiener
No full textIn questo lavoro vengono introdotte delle estensioni alla procedura di identificazione detta nonlinear auto-tune variation (Natv) proposta originariamente da Luyben e Eskinat. La tecnica è ben nota dalla letteratura, ma è essenzialmente del tipo trial and error per quanto riguarda la simmetrizzazione del relay. Di seguito viene presentata una soluzione che automatizza completamente il processo di autosintonia sia nel caso di sistemi di tipo Hammerstein che Wiener
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