Medium-Frequency Oscillation in Voltage-Controlled Full-Bridge Inverter with a Nonlinear Inductor

Abstract

An inverter, whose inductor current is periodic, is the key equipment for photovoltaic power generation, fuel cell power generation, etc. A nonlinear inductor, whose inductance will be changed by its current, can be used to improve the grid current quality of the inverter, although making the mathematical model of the inverter system more complex. In this paper, the voltage-controlled full-bridge inverter with a nonlinear inductor is investigated and its mathematical model is established. The influence of parameters on the dynamical behaviors of this system is analyzed by using the harmonic balance method and the Floquet theory. Consequently, the mechanism for the occurrence of medium-frequency oscillation is revealed. The hardware circuit for the voltage-controlled full-bridge inverter with a nonlinear inductor is designed and some experimental results are presented for confirmation. The research results show that the mechanism for the occurrence of medium-frequency oscillation is Hopf bifurcation and its oscillation frequency is between the line frequency and the switching frequency.