A new method on the limit cycle stability analysis of digitally controlled interleaved DC–DC converters

Abstract Nowadays, the requirement to ameliorate efficiency in power conversion systems along with the demand for increased power rating gives rise to the implementation of interleaving operation. Interleaving in conjunction with digital state feedback control provide the ability to create sophisticated control schemes which allow for high efficiency under a wide range of operating conditions and restrictions. Along these lines, the interleaved boost converter finds widespread application in a variety of cases such as battery charging, renewable energy sources and distributed power systems. A very salient aspect concerning the performance of the converter is the occurrence of limit cycle instabilities that can have an adverse effect on the operation of the converter resulting in efficiency and lifetime reduction. These instabilities are a trait of the piecewise linear nature of the system dynamics, in which case, a bifurcation analysis is required to investigate their influence on the system. However, in the case of interleaving along with digital control the standard implementation of the bifurcation analysis for determining the Monodromy matrix is impeded by the dependency of the system of past sampled states. As a consequence, the conventional approaches found in literature are inadequate when it comes to predicting and avoiding these kind of instabilities. This paper addresses the specific issues and presents a novel approach on defining the Monodromy Matrix and deciding upon the stability of the limit cycle. The proposed approach relieves the dependence of the system on past samples by augmenting the first return map with expressions that describe the evolution of the control laws. The interleaved boost converter is used as a case study. Finally, numerical, analytical and experimental results validate our work.