energies Article Adaptive Global Sliding Mode Controller Design for Perturbed DC-DC Buck Converters Saleh Mobayen 1,2, * ,† , Farhad Bayat 1, * ,† , Chun-Chi Lai 3 , Asghar Taheri 1 and Afef Fekih 4   Citation: Mobayen, S.; Bayat, F.; Lai, C.-C.; Taheri. A.; Fekih, A. Adaptive Global Sliding Mode Controller Design for Perturbed DC-DC Buck Converters. Energies 2021, 14, 1249. https://doi.org/10.3390/en14051249 Academic Editor: Teuvo Suntio Received: 24 January 2021 Accepted: 22 February 2021 Published: 25 February 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Electrical Engineering, University of Zanjan, Zanjan 4537138791, Iran; taheri@znu.ac.ir 2 Future Technology Research Center, National Yunlin University of Science and Technology, Yunlin 64002, Taiwan 3 Bachelor Program in Interdisciplinary Studies, National Yunlin University of Science and Technology, Yunlin 64002, Taiwan; cclai@yuntech.edu.tw 4 Electrical and Computer Engineering Department, University of Louisiana at Lafayette, Lafayette, LA 70504, USA; afef.fekih@louisiana.edu * Correspondence: mobayen@znu.ac.ir (S.M.); bayat.farhad@znu.ac.ir (F.B.); Tel.: +98-24-33054219 (S.M.); +98-24-33054071 (F.B.) † These authors contributed equally to this work. Abstract: This paper proposes a novel adaptive intelligent global sliding mode control for the tracking control of a DC-DC buck converter with time-varying uncertainties/disturbances. The proposed control law is formulated using a switching surface that eliminates the reaching phase and ensures the existence of the sliding action from the start. The control law is derived based on the Lyapunov stability theory. The effectiveness of the proposed approach is illustrated via high- fidelity simulations by means of Simscape simulation environment in MATLAB. Satisfactory tracking accuracy, efficient suppression of the chattering phenomenon in the control input, and high robustness against uncertainties/disturbances are among the attributes of the proposed control approach. Keywords: global sliding mode control; DC-DC buck converter; switching surface; adaptive con- troller; lyapunov stability 1. Introduction DC-DC converters are widely employed in various electric power supply systems, such as DC motor drives, computers, cars, ships, aircraft, photovoltaic systems, etc. [1–4]. In those applications where the desired output voltage is smaller than the input voltage a common choice is the buck converter. Because of the nonlinear and time-varying structure of the buck converters owing to their switching operation, the design procedure of high- performance controller for these systems is a challenging topic [5–8]. The main objective of the control method is to confirm the stability of the system in the arbitrary condition with satisfactory dynamic response in the presence of load variations, parametric uncertainties and external disturbances. Nonlinear and robust control techniques are considered to be the best candidates in DC-DC converter applications than other linear feedback control methods. In the recent years, several nonlinear and robust control schemes have been employed for the stability and tracking control of DC-DC buck converters [9]. Among them, the sliding mode control (SMC) as an effective robust control method has received many applications because of its exceptional robustness against uncertainties and distur- bances, guaranteed stability properties, computational and implementation easiness, fast response and excellent transient performance with respect to other control schemes [10,11]. The sliding mode control method has been prosperously applied to a broad diversity of practical linear and nonlinear systems such as nonholonomic systems [12,13], robot manip- ulators [14], aircraft [15], spacecraft [16,17], underwater vehicles [18], chaotic systems [19], electrical motors [20], and power systems [21,22]. The algorithm of SMC comprises two different phases, i.e., reaching and sliding phases [23]. Due to the impact of the switching Energies 2021, 14, 1249. https://doi.org/10.3390/en14051249 https://www.mdpi.com/journal/energies