Low-Frequency Input Impedance Modeling of Boost Single-Phase PFC Converters

Input impedance models of boost single-phase power factor correction converters suitable for predicting small-signal input characteristics below the line fundamental frequency are presented in this paper. Existing low-frequency input impedance models based on double averaging predicts input current responses to perturbations in the amplitude of the input voltage. It is shown in this paper that such impedance models do not conform to the standard definition of impedance, and, hence, cannot be used in conjunction with the source output impedance to study system interactions based on the Nyquist stability criterion, as traditionally done in dc power systems. A new input impedance model that overcomes this problem is developed by using the method of harmonic balance. The new model conforms to the standard definition of impedance and predicts input current responses to superimposed input harmonic voltages. Numerical simulation and experimental results are presented to validate the proposed model. Mathematical relationship between the two types of models are also presented.