A Describing Function-Based Stability Analysis Method for Cascaded DC-DC Converters

Abstract

The parameters of each DC-DC converter in a cascaded converters system are often set up separately, which may cause instability or even breakdown of the whole system. The traditional Middlebrook impedance stability criterion and Nyquist criterion are based on the small-signal model, where the non-linear links are ignored or linearized, however, which leads to inaccurate modeling, and the stability range cannot be obtained analytically. In this paper, the non-linear links, i.e. pulse width modulation links, of cascaded DC-DC converters system are first modeled by the describing function; then, a novel stability analysis method for the cascaded DC-DC converters system is proposed by combining the impedance analysis method, Nyquist criterion and describing function, by which, the accurate stability range of the converter control parameters can be derived. Since the describing function method is only applicable to a single converter, in order to apply it to the cascaded converters, a source/load converter equivalent method is proposed. To this end, a two-stage cascaded boost converters system is taken as an example, and the simulation and experiment are conducted to verify the correctness and accuracy of the proposed stability analysis method. It provides an analytical method to determine not only the stable and unstable ranges but also the critical stability range of the cascaded system, namely, a quantifiable stability range of control parameters.INDEX TERMS Stability analysis method, cascaded DC-DC converters, describing function.

Kendali arus dan tegangan pada konverter DC-DC boost dengan metode kaskade proportional integral derivative

“…Kendali metode propotional integral (PI) merupakan salah satu kendali klasik yang sampai saat ini masih sangat diandalkan dalam teknik pengendalian. Konverter DC-DC jenis kaskade boost yang berfungsi untuk meningkatkan tegangan keluaran dua kali lipat dari tegangan masukan dengan sistem pengendalian yang terintegrasi menjadi satu guna meningkatkan stabilitas pada sistem [5]. Selain kendali pada konverter, kendali modern yang diusulkan juga dapat memperbaiki kinerja dan optimalisasi dari topologi konverter [6]- [7].…”

Multistability and Its Control by the PWM Carrier Signal Modulation in a DC Electric Drive System

“…From the practitioner's point of view, such nonlinear behavior is an undesired feature; therefore, the mechanism of their onset has to be clear. Recent studies are also devoted to the analysis of more complex power converter systems, such as multicell fying capacitor converters [10], LLC resonant converters [11], cascaded DC/DC converters [12], just to name a few, and also those in connection with the nonlinear source or load, such as photovoltaic module [13]. Onset of instability in such complex systems is also caused by the reasons, which difer from those that were depicted in the classic literature, like an interaction between the load and source converter in a cascaded system [14].…”