Assessment of an Average Controller for a DC/DC Converter via Either a PWM or a Sigma-Delta-Modulator

R Silva-Ortigoza,H Taud,D Muñoz-Carrillo,J J Gálvez-Gamboa,M Marcelino-Aranda,F Carrizosa-Corral

doi:10.1155/2014/196010

Abstract

Sliding mode control is a discontinuous control technique that is, by its nature, appropriate for controlling variable structure systems, such as the switch regulated systems employed in power electronics. However, when designing control laws based on the average models of these systems a modulator is necessary for their experimental implementation. Among the most widely used modulators in power electronics are the pulse width modulation (PWM) and, more recently, the sigma-delta-modulator (Σ-Δ-modulator). Based on the importance of achieving an appropriate implementation of average control laws and the relevance of the trajectory tracking task in DC/DC power converters, for the first time, this research presents the assessment of the experimental results obtained when one of these controllers is implemented through either a PWM or aΣ-Δ-modulator to perform such a task. A comparative assessment based on the integral square error (ISE) index shows that, at frequencies with similar efficiency, theΣ-Δ-modulator provides a better tracking performance for the DC/DC Buck converter. In this paper, an average control based on differential flatness was used to perform the experiments. It is worth mentioning that a different trajectory tracking controller could have been selected for this research.

Highlights

Sliding mode control is a well-known discontinuous feedback control technique which has been exhaustively explored in many books and journal articles by various authors
Using [22, 23], the Appendix presented in this paper describes the most relevant characteristics associated with the implementation of average controllers via a Σ-Δ-modulator
(iii) Modulator stage, which converts the average control signal into a switched signal, via either a pulse width modulation (PWM) or a Σ-Δ-modulator: two characteristics of this stage are highlighted: (1) it produces the complement of u, that is, u, which will appropriately activate the NTE2984 Mosfet since the NTE3087 optocoupler inverts the logical input; (2) following the analysis presented in [50], since the proposed sampling frequency for the Σ-Δ-modulator was 25 kHz, a corresponding frequency for the PWM that achieves a similar efficiency to that of the Σ-Δ-modulator is 12.5 kHz

Summary

Introduction

Sliding mode control is a well-known discontinuous feedback control technique which has been exhaustively explored in many books and journal articles by various authors. A complete account of the history and fundamental results of sliding modes is found in books, such as those presented by Emelyanov [1], Utkin [2, 3], and Utkin et al [4]. Well-documented books that contain chapters on sliding mode control are those of Slotine and Li [6], Sastry [7], Kwatny and Blankenship [8], and Zak [9], among others. Other interesting works about applications of sliding modes are those presented in [14,15,16] and the references therein. Applications to DC/DC power converter-DC motor systems have been reported in [20, 21]

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Conclusion