Transient Response Improvement of Buck Converter through Sliding Mode controller

Abstract

Power electronic converters are integral part of the modern power system. Fast dynamic response along with low cost and small size of DC-DC converters are responsible for their increasing use in renewable energy interface, electric vehicles, telecommunications, control and switched mode power supplies. Step down buck converter is one of the most commonly used DC-DC converter topology. PI controllers failed to control dynamics of buck converter under line and load variations. Sliding mode controller is a nonlinear controller and offers advantages of robustness, fast dynamic response and ease of implementation. In this paper, SMC is proposed to control dynamics of buck converter. Proposed controller is combination of linear control and nonlinear control. Linear control is implemented through PI and is derived from voltage loop of the buck converter. Nonlinear part of the controller is implemented through hysteresis. Inductor current ripple is used to select ON and OFF points of the hysteresis control. Proposed controller for buck converter is simulated using MATLAB®/SIMULINK® software. Simulation analysis confirms effectiveness of the proposed SMC. Overshoot in output voltage and inductor current is eliminated for initial transient and line variation. Very small overshoot in output voltage is observed for load variation