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A new digital robust control law for dc-dc converters is analyzed and implemented in this paper. The robust control QFT technique, which has been successfully used with analog implementations, has been adapted to the digital domain. Concretely, this paper considers the design of a power conditioning unit, which must take into account the uncertainty of the converter, as the conduction mode, the load, the input voltage or the storage elements while assuring that the specifications of a well-known standard are met. The robust control has been implemented by means of a digital device. The sampling frequency is a critical parameter for this kind of system which exhibits fast dynamics. The paper shows a procedure to analyze the minimum sampling frequency of the regulation loop. The procedure consists of transforming an standard analog QFT design to a digital controller by means of an accurate transformation from the s to z domain. After this transformation, we assure the robust stability of the converter by means of the Kharitonov theorem. This approach allows the designer to avoid iterations while finding an appropriate sampling frequency. The experimental prototype has been implemented by means of a FPGA device where the sampling frequency is 100 kHz for a buck power stage with a switching frequency of 200 kHz. The experimental results that are in good agreement with theoretical derivations. [ABSTRACT FROM AUTHOR]

This paper deals with the modeling and the robust controller synthesis for nonlinear dc–dc converters. In the first part of this paper, a model for the bilinear dynamics is presented. Such nonlinear dynamics can be included in a convex polytope such that the trajectories of the converter out of the equilibrium are assured to remain inside a guaranteed region of stability despite of the bilinear term. Such a description of the dynamic response of the converter is employed, in the second part of this paper, to propose synthesis algorithms that can guarantee, a priori, the stability and performance requirements of the design. The resulting region of stability can take into account not only the bilinear terms but also the saturation of the control input, which is a topic of major importance in high-performance dc–dc converters. The aim of this paper is to contribute with a robust control framework which allows the designers to deal with the common requirements of regulated dc–dc converters. The correctness of the results has been verified both with numerical simulations and experimental measurements from dc–dc converter prototypes. [ABSTRACT FROM PUBLISHER]

A design method using quantitative feedback theory (QFT) for robust control of PWM DC-DC converters is developed. Parametric and nonparametric uncertainty can be described accurately with this technique. Besides, with the proposed method, the controller can consider both continuous and discontinuous conduction mode models (CCM and DCM respectively). Considering these sources of uncertainty results in a robust controller insensitive to parametric variations and also to different plant cases due to different conduction modes. A power converter satisfying a well-known industry standard is presented as a design example, in order to demonstrate that, with the proposed procedure, the performance of the regulated system can be tightly specified not only in terms of frequency requirements, but also in terms of time-domain characteristics, like overshoot and establishment time. The synthesised robust controller has been verified with experimental data from a power converter prototype, achieving satisfactory results. [ABSTRACT FROM AUTHOR]

This paper presents two different robust controllers for boost converters with two stages in a cascade. The first robust controller is monovariable; that is, the duty-cycle is the same for the two switches. The monovanable controller ensures that some prescribed constraints on pole placement and control effort are met, and optimizes the load disturbance rejection, while takes into account the uncertainty in certain parameters. The first controller is then compared with a multivariable robust controller; that is, with independent duty cycles in each switch. The multivariable controller takes into account the same uncertainty, constraints and optimization function. The comparison shows that the multivariable controller performs better at the expense of a slightly more complex implementation; that is, the multivanable controller provides a better rejection of the load disturbance. The paper also describes simulations and experimental results that are in perfect agreement with theoretical derivations. [ABSTRACT FROM AUTHOR]