This paper presents a Hysteresis Modulation based Sliding Mode Controller (HMSMC), for single stage three level full bridge ac-dc converter under discontinuous conduction mode (DCM). Compared with the conventional methods like PI, fuzzy and sliding mode controller, this HMSMC is capable of attaining the improved steady state and large signal transient response under variations occur at supply and load side. State space averaging method is used here to derive the dynamic equations of the converter. Also, using the theory of hysteresis modulation for wide operating region derives the switching frequency of the converter. The Simulink model of the presented PFC ac-dc converter with HMSMC circuit is verified with Matlab/Simulink. The HMSMC for the converter is analyzed for line variations, load variations and for non-linear component variations.

Keywords: Three level full bridge ac-dc converter, Hysteresis modulation-based sliding mode controller (HMSMC), Discontinuous conduction mode (DCM), Line and load variations