MODELLING, ANALYSIS AND CONTROL OF NON-IDEAL SEPIC DC-DC CONVERTER

Abstract

This thesis presents the design and comparative analysis of PI and PID controllers for a non-ideal SEPIC DC-DC converter intended for electric vehicle charging applications. The converter is configured to step up a 24V input to a regulated 48V output under Voltage Mode Control. A complete non-ideal small-signal model is derived by the State-Space Averaging technique, taking into account inductors, capacitors, switching devices and input source parasitic resistances, leading to a fourth-order control-to-output transfer function. Two systematic tuning methods, the classical Cohen-coon method and the model based Internal Model Control (IMC) approach, are investigated and compared. Both the controllers are implemented and evaluated with the help of circuit level simulation in MATLAB/Simulink. The performance is evaluated in terms of transient response characteristics such as rise time, settling time and overshoot and disturbance rejection capability under input voltage and load variations. The comparison reveals the relative merits of each tuning method and gives a systematic basis for controller choice in non-ideal DC-DC converter applications.