Search

The design of fourth-order dc-dc converters is discussed in this paper. The Principal Components Analysis is applied to find the set of passive components which allows to avoid double resonance in the control-to-output transfer function. The design of a synchronous SEPIC converter has been studied as an application of the proposed design methodology by using a database of real passive components. The performances of the SEPIC converter designed with the proposed methodology are verified through both time domain and frequency domain simulations and they are compared with those ones achieved by standard ripple-based design procedures. Index Terms--Fourth-order converters, power stage design, principal components analysis, SEPIC converter.

In this paper, the design of the one-cycle controller of a single-stage inverter for photovoltaic applications is carried out by means of a multiobjective strategy to optimize inverter performance at both high and low insolation levels. Design constraints that account for different weather conditions are adopted. The optimization algorithm also provides useful information concerning the system sensitivity with respect to each of the controller parameters. This allows the design of a maximum power point tracking perturb and observe controller that significantly improves inverter performance. Experimental measurements confirm the predictions of theoretical and simulation results. Index Terms--Maximum power point tracking (MPPT) techniques, one-cycle control (OCC), photovoltaic (PV) inverter.

One of the major drawbacks of photovoltaic (PV) systems is represented by the effect of module mismatching and of partial shading of the PV field. Distributed maximum power point tracking (DMPPT) is a very promising technique that allows the increase of efficiency and reliability of such systems. Modeling and designing a PV system with DMPPT is remarkably more complex than implementing a standard MPPT technique. In this paper, a DMPPT system for PV arrays is proposed and analyzed. A dc and small-signal ac model is derived to analyze steady-state behavior, as well as dynamics and stability, of the whole system. Finally, simulation results are reported and discussed. Index Terms--Distributed generation, maximum power point tracking (MPPT) techniques, photovoltaic (PV) systems.

Power processing systems will be a key factor of future photovoltaic (PV) applications. They will play a central role in transferring, to the load and/or to the grid, the electric power produced by the high-efficiency PV cells of the next generation. In order to come up the expectations related to the use of solar energy for producing electrical energy, such systems must ensure high efficiency, modularity, and, particularly, high reliability. The goal of this paper is to provide an overview of the open problems related to PV power processing systems and to focus the attention of researchers and industries on present and future challenges in this field. Index Terms--Inverters, maximum power point tracking (MPPT), photovoltaic (PV) systems, power electronics, power processing, solar energy.

Maximum power point tracking (MPPT) techniques are used in photovoltaic (PV) systems to maximize the PV array output power by tracking continuously the maximum power point (MPP) which depends on panels temperature and on irradiance conditions. The issue of MPPT has been addressed in different ways in the literature but, especially for low-cost implementations, the perturb and observe (P&O) maximum power point tracking algorithm is the most commonly used method due to its ease of implementation. A drawback of P&O is that, at steady state, the operating point oscillates around the MPP giving rise to the waste of some amount of available energy; moreover, it is well known that the P&O algorithm can be confused during those time intervals characterized by rapidly changing atmospheric conditions. In this paper it is shown that, in order to limit the negative effects associated to the above drawbacks, the P&O MPPT parameters must be customized to the dynamic behavior of the specific converter adopted. A theoretical analysis allowing the optimal choice of such parameters is also carried out. Results of experimental measurements are in agreement with the predictions of theoretical analysis. Index Terms--Maximum power point (MPP), maximum power point tracking (MPPT), perturb and observe (P&O), photovoltaic (PV).

An 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 cast of components. Simulation results show the wide usefulness of the proposed method in supporting designer decisions.

This paper introduces an evolutionary approach to the variability analysis of nonlinear systems. The algorithm shows some advantages with respect to classical stochastic approaches and, in particular, with respect to Monte Carlo-based methods. First, it allows a significant reduction of the underestimation error that affects any nondeterministic approach; in other words, it guarantees a considerable saving of simulation time. Moreover, the technique ensures a higher reliability in pursuing the true range of variation of the system performance of interest. The method has been applied to a practical problem of great interest: the variability analysis of a stress control tube made of a composite material used for electric stress relief in cable accessories. The cable termination has been modeled by means of a lumped nonlinear circuit. The proposed technique also provides reliable results whenever large parameter variations need to be taken into account and/or nonlinear functions of varying parameters are considered. Simulation results prove it to be of great support for the designer in cable termination dimensioning and in composite material selection. Index Terms--Cable accessories, composite materials, variability analysis.