en Nonlinear Control Nonlinear Control Research Paper Research Paper In this paper, the problem of controlling PWM single-phase AC/DC converters is addressed. The control objectives are twofold: (i) regulating the output voltage to a selected reference value, and (ii) ensuring a unitary power factor by forcing the grid current to be in phase with the grid voltage.  To achieve these objectives, the singular perturbation technique is used to prove that the power factor correction can be done in the open-loop system with respect to certain conditions that are not likely to take place in reality. It is also applied to fulfill the control objectives in the closed-loop through a cascade nonlinear controller based on the three-time scale singular perturbation theory. Additionally, this study develops a rigorous and complete formal stability analysis, based on multi-time-scale singular perturbation and averaging theory, to examine the performance of the proposed controller. The theoretical results have been validated by numerical simulation in MATLAB/Simulink/SimPowerSystems environment. Singular Perturbation, PWM AC/DC Converters, Nonlinear Control, Power Factor Correction, Averaging Theory, Stability Analysis. 2013 2013 http://ijeee.iust.ac.ir/browse.php?a_code=A-10-3625-1&slc_lang=en&sid=1 Y. Mchaouar youssef.mchaouar-etu@etu.univh2c.ma 1800319475328460010056 1800319475328460010056 Yes TI Lab., Faculty of Sciences Ben M'sik, Hassan II University of Casablanca, Casablanca, Morocco. A. Abouloifa A.ABOULOIFA@gmail.com 1800319475328460010057 1800319475328460010057 No TI Lab., Faculty of Sciences Ben M'sik, Hassan II University of Casablanca, Casablanca, Morocco. I. Lachkar lachkaribtissam@gmail.com 1800319475328460010058 1800319475328460010058 No ESE Laboratory, ENSEM, Hassan II University of Casablanca, Casablanca, Morocco. H. Katir katir.hanane@gmail.com 1800319475328460010059 1800319475328460010059 No TI Lab., Faculty of Sciences Ben M'sik, Hassan II University of Casablanca, Casablanca, Morocco. F. Giri fouad.giri@unicaen.fr 1800319475328460010060 1800319475328460010060 No Automatic Laboratory of Caen (LAC), National Graduate School of Engineering of Caen (ENSICAEN), University of Caen Normandy, Caen, France. A. El Aroudi abdelali.elaroudi@urv.cat 1800319475328460010061 1800319475328460010061 No Department of Electronic, Electrical and Automatic Engineering, University of Rovira i Virgili (URV), Tarragona, Spain. A. Elallali aichaelallali@gmail.com 1800319475328460010062 1800319475328460010062 No TI Lab., Faculty of Sciences Ben M'sik, Hassan II University of Casablanca, Casablanca, Morocco. C. Taghzaoui taghzaouichaimaa@gmail.com 1800319475328460010063 1800319475328460010063 No TI Lab., Faculty of Sciences Ben M'sik, Hassan II University of Casablanca, Casablanca, Morocco.