Robust Reference Tracking and Load Rejection on Non-Linear System Using Controllers

Abstract

DC-DC converters form a class of highly nonlinear systems and are widely used in most practical applications. Positive Output Elementary Luo Converter (POELC) is a fourth-order converter used to regulate dc voltages in low power applications with varying input voltage and load conditions. POELC is employed to regulate dc voltages for sensitive load applications like SMPS, powering hard disks etc. The control of higher-order converters is always a challenging task due to the highly nonlinear nature of these converters. Hence the development of an optimal controller for POELC is proposed in this paper. The proposed control methods are investigated for transient and steady-state performances considering practical operating conditions. The controllers are designed, simulated and the performance of POELC with various controllers is evaluated in the MATLAB/Simulink environment. The PI controller exhibits better performance in the linear region whereas, in the nonlinear region, due to time variance and switching nature. To minimize the sensitivity to external disturbances and to improve the stability margins, an LQR is designed to regulate the output of POELC. The result shows that a well-designed LQR feedback can stabilize the system and enhances its performance in terms of Integral Absolute Error (IAE), Integral Square Error (ISE). Certain case studies are discussed concerning practical applications.