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A consistent framework for robust linear quadratic regulators (LQRs) control of power converters is presented. Systems with conventional LQR controllers present good stability properties and are optimal with respect to a certain performance index. However, LQR control does not assure robust stability when the system is highly uncertain. In this paper, a convex model of converter dynamics is obtained taking into account uncertainty of parameters. In addition, the LQR control for switching converters is reviewed. In order to apply the LQR control in the uncertain converter case, we propose to optimize the performance index by using linear matrix inequalities (LMIs). As a consequence, a new robust control method for dc-dc converters is derived. This LMI-LQR control is compared with classical LQR control when designing a boost regulator. Performance of both cases is discussed for load and line perturbations, working at nominal and nonnominal conditions. Finally, the correctness of the proposed approach is verified with experimental prototypes. Index Terms--Optimal control, power electronics, robustness.

In this paper, the problem of paralleling dc-dc switching converters is solved by means of power gyrators. The key element of the parallel connection is a buck converter with input filter acting as a power gyrator of type G with controlled output current, i.e., with its dc output current being proportional to its dc input voltage, electromagnetic interference minimization, current distribution among converters, stability, and voltage regulation are ensured by this approach. It is shown that a voltage regulator based on the parallel operation of power gyrators with democratic current sharing is always stable regardless of the number of connected modules. Experimental results of a dc-dc voltage regulator based on the parallel connection of three power gyrators with democratic current sharing are in perfect agreement with the theoretical predictions. Index Terms--Converter paralleling, gyrators, stability and voltage regulation.

Using a systematic procedure for classifying resonant converters, we have synthesized a zero-voltage switching resonant structure with inherent short-circuit protection. We analyze the operating modes of the disclosed converter and derive the control characteristic curve. Experimental verification is presented in a 100-W prototype. Index Terms--Nonresonant coupling, nonresonant driving, resonant converters, short-circuit protection., synthesis, zero-voltage switching (ZVS).

This paper investigates the use of neural networks for identification and control of power converters. A nonparametric model of a dc-to-dc switching converter implemented by means of a neural network emulator identifies the converter dynamics in cases of uncertainty in the load parameter. A pseudolinearization control technique resulting in converter regulation and closed-loop linear dynamic behavior is also implemented by means of a neural controller. Simulation results in a PWM boost converter under large-signal operation illustrate both applications. Index Terms - Converters, neural networks, pseudolinearization.

A quasi-periodic route to chaos is studied both numerically and experimentally in a dc--dc boost switching regulator. After undergoing a Neimark--Sacker bifurcation of a one-periodic orbit, quasi-periodic behavior is obtained and the corresponding attractor is a [T.sup.2] torus. Under parameter changes, such torus may breakdown to give chaotic behavior. Two different scenarios are possible for the destruction of the torus. One is obtained by means of period doubling of a phase-locking orbit while the other is achieved by lossing the torus smoothness. An approximated two-dimensional mapping is build-up to predict the nonlinear phenomena detected in this system. Index Terms--Arnold tongues, chaos, dc-dc boost converter, devil staircase, quasi-periodicity.

The problem of stabilizing a boost regulator in large-signal situations using linear control laws is derived by means of a circuit-oriented procedure. After establishing a large-signal circuit model for the boost regulator including state-feedback, conditions for passivity in the resulting two-port are studied. As a consequence, a linear control law is derived, thus ensuring regulator global stability even if the control saturation is taken into account. Subsequently, a linear analysis is performed, in order to design the desired dynamics and robust behavior of the switching regulator. The nonlinear analysis shows that only one feedback gain is necessary, provided that the coordinates of the equilibrium point are known. The use of regulator root locus allows to choose the proper value of this gain. Simulations and experimental results verify the analytical predictions. Index Terms--Converters, large-signal stability, passivity.