Dynamical behaviour and stability analysis in SEPIC converter based on sliding-mode control

A hysteretic current-controlled SEPIC converter, which uses the sum of two inductorcurrents as the control variable, is discussed. The operation states of the converter are studied basedon the theory of sliding-mode control. The equivalent control and relative differential equations onthe sliding surface are derived, based on which, the stability of equilibrium point is analysed with thecalculation of eigen-values. With numerical calculation and computer simulation, it is shown that theequilibrium point will lose the stability via a Hopf bifurcation when the reference current increases.The other circuit parameters will make infl uence on the fi rst bifurcation point of reference current.Subsequently, the converter will exhibit complex dynamical behaviour, including limit cycle, doublelimit cycle, quasi-periodicity and chaos, by increasing the reference current furthermore.