A comparative analysis of nonlinear current control schemes applied to a SEPIC Power Factor Corrector

In this paper, a comparative analysis of two nonlinear control schemes proposed for a Single Ended Primary Inductance Converter (SEPIC) Power Factor Corrector (PFC) is presented. The SEPIC converter, compared to conventional buck or boost ones, allows a low current ripple at the input for a relatively low level of the DC-bus voltage Consequently, the high frequency filter needed at the AC-side of a buck converter is avoided, and the high voltage stresses applied on the switches are significantly reduced with respect to the boost converter. The converter is integrated at the DC-end of a single-phase diode bridge. In order to ensure a unity power factor at the AC-source side and a regulated voltage at the DC-load side, a multiple-loops feedback control scheme has to be developed. Two control strategies are considered in this paper. The first one uses a robust hysteresis current controller, whereas the other method is based on the application of the input/output feedback linearization technique on a state-space averaged model of the converter. In order to verify and compare the performance of both control schemes, numerical simulations are carried out on a switching-functions-based model of the converter, which is implemented using Matlab/Sirnutink. The proposed model of the converter is valid in the Continuous Current Mode (CCM) and the Discontinuous Current Mode (DCM). The control systems are tested under both rated and disturbed operating conditions. The systems performance is evaluated in terms of source current Total Harmonic Distortion (THD), input power factor, DC voltage regulation and robustness toward a load disturbance.