1,721,166 research outputs found
Tolerance design of controllers for switching regulators
No full textAn evolutionary approach to worst case tolerance design is introduced here, with a focus on feedback compensation networks for dc-dc switching converters. Assumed that varying parameters values are uniformly distributed and uncorrelated, as provided by the worst case approach, the proposed algorithm, of general applicability, seeks for the set of nominal values and tolerances of the circuit parameters ensuring that the design constraints are met and that a user-defined circuit performance index assumes its optimal value. Design constraints, are fixed in the frequency domain, in terms of acceptability ranges of loop gain crossover frequency and phase margin, to guarantee closed loop stability and the desired dynamic performance. Resistive and capacitive compensation network's parameters values are chosen within a suitable database of couples nominal value/tolerance available on the market, while the nominal values and tolerances of the parameters of the power stage are fixed. Referring to a buck dc-dc switching regulator, two widely used different compensation network topologies are compared in terms of reliability, robustness, and cost of components. Simulation results show the wide usefulness of the proposed method in supporting designer decisions
One-cycle controlled power inverters
No full textOne Cycle control is a technique matching many features that are typical of the linear control methods with some others that characterise high performances non-linear control approaches. Indeed, it ensures a constant switching frequency with a high promptness and noise rejection. The One Cycle control technique has recently found applications in many fields related to the renewable energies and to the power factor control, so that the customersâ interest is increasing. In this chapter the basic elements of the One Cycle control technique are reviewed and some issues related to its wide applications are discussed. A special emphasis is given to the DC/AC single-phase conversion
A PARALLEL NON-PROBABILISTICALLY-DOMINATED SORTING GENETIC ALGORITHM FOR ROBUST OPTIMIZATION
Full text linkSuccessful engineering design generally requires the resolution of various conflicting design objectives. In order to identify an optimal design, conflicting objectives are typically considered simultaneously. One of the most powerful tools for resolving such objectives, in a computational setting, is multi-objective optimization. By definition, Pareto solutions are considered optimal because there are no other designs that are superior in all objectives.
In a deterministic optimization the effect of uncertainty is not considered when drawing conclusions, hence we want to extend the concept of Pareto dominance in a probabilistic sense.
In each evolution era, the different chromosomes can be evaluated with respect to the objective functions in parallel. For each one of the chromosome the Simplex Stochastic Collocation is used to handle uncertainty. The method is based on a serial sequential-solution refinement of the probability space until a defined threshold: different simplexes converge at different times.
A nested loop of parallel-serial evaluations is handled by the R-Opt to achieve the best computational efficiency
An hybrid digital-analog sliding mode controller for photovoltaic applications
No full textSliding mode is a control technique that is widely employed in switching converter applications. Such a non-linear control technique, which is commonly implemented by means of analog circuitry only, forces the switches commutations by comparing a reference signal with a combination of signals acquired on the converter itself. In this way, the control action and the switching modulation are integrated in a single functional block. In this paper the implementation of the sliding mode controller in a low cost digital device is discussed. The proposed approach profits from features offered by some digital devices, e.g. the dsPic33FJ16GS502 family from Microchip Technology Inc., in order to make the implementation simple. In the paper, the aspects related to the accuracy of the comparison between the signals required by the sliding mode controller are discussed. Moreover, the elaboration time needed to calculate the signals that drive the converters switching devices is the subject of an in-depth analysis. The techniques proposed in the paper have been validated by means of simulations and through experimental results performed on a switching dc/dc converter for photovoltaic applications
Multi-Disciplinary Design And Analysis Of Wind Turbines Under Uncertainty
No full textThe performance of wind turbines can be negatively affected by the presence of uncertainties. We introduce a comprehensive multi-physics computational model EOLO that enables the estimation of aerodynamic and structural characteristics assiociated with horizontal axis wind turbines, and use it to study the impact of uncertainties on the aerodynamic performance and noise. We consider variability in the wind conditions, manufacturing tolerances and roughness induced by
insect contamination as sources of uncertainties and treat them within a probabilistic framework using Latin Hypercube Sampling and Stochastic Simplex Colocation. The results demonstrate that these two methods lead to a statistical characterization of the quantity of interest which is considerably faster than classical Monte Carlo methods. In addition, we demonstrate how the uncertainties impact the aerodynamics and noise leading to a largely inferior performance compared to the nominal design. Finally a multi-disciplinary shape optimization of the wind turbine blade is proposed
An interval arithmetic-based method for parametric identification of a fuel cell equivalent circuit model
Full text linkIn this paper, the identification of the equivalent circuit parameters of a polymer electrolyte fuel cell stack is performed for diagnostic and monitoring purposes. An interval arithmetic branch and bound method is developed for the identification of parameters of the Fouquet model, frequently used for fuel cell modeling in the frequency domain. The proposed method allows to bound each parameter by an interval of real values. It also provides the model sensitivity with respect to the parameters. The method is also able to account for uncertainties affecting the impedance measurements at the assigned frequency values. For the specific application to fuel cells, the approach overcomes the limitations, in terms of interval contraction capability, characterising standard interval analysis-based techniques. The features of the proposed approach, shown with various examples also involving experimental measurements, are useful in monitoring the stack performance, to the final aim of improving its lifetime, and ensuring the expected electrical power production. The proposed results allow to envisage an application of the method also in real time conditions, when the fuel cell model parametric identification has to be run by using an embedded system instead of a personal computer
Experimental evaluation of a MPPT technique for electrical mobility PV applications
No full textIn this paper the performance of a maximum power point technique, which is suitable for photovoltaic applications to sustainable mobility, is documented. The approach is based on the use of one DC/DC converter per sub-section of the photovoltaic array, with a central controller that changes the duty cycle of each DC/DC converter in a way that the current injected into the battery is maximized. The control has been implemented by programming a Microchip controller through Simulink in order to have a fast prototyping. The experimental measurements, obtained during the regular driving of the vehicle, reveal the superiority of the technique in order to maximize the power harvested from the cells that are differently oriented with respect to the sun rays. The results are achieved in the frame the European Union's Horizon 2020 research and innovation program under grant agreement No. 653288 - OPTEMUS
Parameters identification of the single-diode model for amorphous photovoltaic panels
No full textThe single-diode model, which is widely used for describing the behaviour of the photovoltaic crystalline and multi-crystalline cells, requires to be properly adapted for reproducing the electrical behaviour of amorphous thin film silicon cells. As for the former case, five parameters must be identified for having a good fitting with respect to the experimental measurements or the data reported in the module data sheet. Nevertheless, due to the strong nonlinearity of the model, the fitting procedures suffer from convergency problems and are sensible to the initial guess solution. In this paper a set of explicit equations is developed in order to calculate the approximated values of the five parameters characterising the PV model. These equation have been obtained by extending, to the amorphous case, the procedure already developed for the crystalline single diode model, thus by generalising and reinforcing the validity of that approach. The new formulas have been validated by comparing the results of the proposed approach with the experimental values reported in the data sheet of some amorphous silicon panels
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