Simplified model for analysis of harmonic distortions in AC buck converter

Authors: Gorbunov R. L., Poskonnyy G. I.

Annotation: In this paper the simplified model of the AC buck converter switching unit in the form of equivalent controlled non-sine current and voltage sources is proposed. The model suitable for harmonic distortions analysis and can be used with direct methods of power indexes analysis in switching converters. The model allows determining the main harmonic distortion indexes of currents and voltages in different filter configurations and different types of load. In contrast to the switching functions method, the section-stick method, computer or numerical simulation, the results of analysis by use of the proposed model present finite analytical formulas, which allow calculation of required distortion indexes and in an explicit form include the main parameters of control algorithm and circuits of converter. An example of analysis of the system with the single-stage input filter, the power converter and the induction motor is described. Theoretical results are compared with the results of computer simulation and experiment.

Keywords: ac buck converter, harmonic distortions, mathematical model, equal time-ratio control, total harmonic distortion, harmonic distortion ratio