Analysis of Slow-Scale Instability in Boost PFC Converter Using the Method of Harmonic Balance and Floquet Theory

In this paper, the slow-scale instability in a boost PFC converter under average current mode control is studied via the harmonic balance method and Floquet theory. Systematic and general numerical algorithm of the technique is developed. The objective is to identify instability of the system. If instability exists, the type of bifurcation and the boundaries of slow-scale instability in the parameter space of the system can be found for facilitating the design of such converters. Firstly, based on the fact that the current compensator is designed very well and what we considered is the slow-scale instability, the simplified model of a boost PFC converter under average current mode control is derived. And then, the solution of the simplified model is calculated by using the harmonic balance method. Subsequently, both the stability of the circuit system and the type of bifurcation are identified via Floquet theory. Meanwhile, the critical conditions of the stable operation in the parameter space of the system are given accurately. Finally, experimental results are presented for the verification of the analytical results.