Comparative Study of Two Average-Model-Based PWM Control Schemes for a Sheppard-Taylor PFC

In this paper, a comparative evaluation of two control strategies applied on the single-phase Sheppard-Taylor power factor corrector (PFC) is proposed. Both control laws generate fixed-frequency carrier-based pulse-width-modulation (PWM) gate signals, and are designed on the basis of the nonlinear averaged model of the converter, which is established using the well-known state-space averaging technique. The first control approach employs linear PI regulators for both input current wave-shaping and output voltage regulation. For this purpose, the derivation of the converter's small-signal transfer functions was required. The second control uses the input-output feedback linearization strategy in order to compensate the system's nonlinearity and simply, thus, the controllers design. The performance of both control schemes is tested through simulations. The comparison is conducted in terms of source current total harmonic distortion (THD), input power factor and DC-voltage regulation.