CONTROLLER DESIGN FOR SEPIC CONVERTER USING MODEL ORDER REDUCTION

A SEPIC (Single-Ended Primary Inductor Converter) is a DC-DC converter, capable of operating both in stepup or step-down mode and widely used in battery-operated applications. There are two possible modes of operation in the SEPIC converter: Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM). This paper presents modeling of a SEPIC converter operating in CCM using the State-Space Averaging (SSA) technique. SEPIC converter consists of two inductor and two capacitor hence it is fourth order dc-dc converter. Design of feedback compensator for fourth order system is quite complex. In this paper, model order reduction technique is used for controller design of SEPIC converter. First small signal dynamic model for SEPIC converter is obtained using SSA technique which provides fourth order transfer function. Then this fourth order transfer function is reduced to second order using Padé approximation. Then the compensator is designed for the reduced order model of the SEPIC converter. Result shows that the compensator designed for reduced order model gives the quite satisfactory response with the original system