Input impedance modeling of single-phase PFC by the method of harmonic linearization

High-frequency input impedance modeling of single-phase PFC converters controlled by a new nonlinear average current control method is presented in this paper. The nonlinear control results in a nonlinear current loop model which is time-varying and cannot be linearized by conventional small-signal analysis or reduced-order modeling techniques. The proposed harmonic linearization method solves this problem by linearizing the model along the trajectory of the input current at the fundamental frequency. The resulting input impedance model is valid above the crossover frequency of the voltage loop and can be used to predict high-frequency interactions between the PFC converter with its EMI filter and the ac source. The principle of harmonic linearization is presented along with detailed development of the input impedance model and its verification by experimental measurement results. The input impedance model is further used to compare the nonlinear average current control method with other single-phase PFC control methods.