Input Impedance Modeling and Analysis of Line-Commutated Rectifiers

This paper presents the modeling and analysis of small-signal input impedance for line-commutated rectifiers. The recently developed impedance mapping method, which has been applied to single-phase rectifiers with sinusoidal line inputs, is generalized to single-phase rectifiers with distorted lines as well as three-phase rectifiers. The modeling method assumes known impedance of the circuit on the dc side of the rectifier bridge (including its output filter and the load), and determines the corresponding ac input impedance by using a current and voltage mapping function which describes the operation of the rectifier bridge in the frequency domain. In this approach, closed-form analytical expressions are derived for the ac input impedance as functions of the dc circuit impedance. The resulting models are intended for stability analysis and design of large ac power systems involving significant number of rectification loads, such as more-electric aircraft power systems and microgrids. Detailed derivation of the models is presented in this paper. Numerical simulation and experimental measurement results are also presented to validate the derived models.