Modeling and Control of a Single-Phase Sheppard-Taylor Based Power Factor Corrector

In this paper, a single-phase power factor corrector (PFC) based on the Sheppard-Taylor topology is presented. Compared to conventional buck, boost or buck-boost PFCs, this topology allows a better current tracking at the AC side, with a relatively reduced voltage at the DC side. Consequently, the high frequency AC filters required by the buck PFCs are avoided, and the voltage stresses on the boost switches are significantly reduced. Furthermore, the control detuning phenomenon from which suffer most of the conventional PFCs, especially at very low input voltage, is avoided. This yields major improvements in the source current waveform. The proposed converter is integrated as a PFC at the DC-end of a single-phase diode bridge. A pulse-width-modulated (PWM) control is developed in order to ensure a unity power factor at the AC-source side and a regulated voltage at the DC-load side. In order to verify the performance of the proposed control scheme, simulation experiments are carried out on a numerical version of the converter with its control circuit. The implemented model of the converter is obtained by using the switching function technique. The control system is tested under both rated and disturbed operating conditions. The system performance is evaluated in terms of source current total harmonic distortion (THD), voltage regulation, robustness and dynamic time response to a set point offset.