Analysis of Chaos in Three-Level Full-Bridge Converter

As an important part in the active magnetic bearing, its performance has great impact on the active magnetic bearing system. Most of the active magnetic bearing systems use current-mode switching power amplifiers. The full-bridge converter is the main topological structure of switching power amplifier for magnetic bearings. It mainly supplies current to the coil so it can offer enough fore to the rotor. It has abundant nonlinear phenomena as the power conversion device of it lies in the nonlinear region. This paper chooses the proportionally controlled three-level switching power amplifier for magnetic bearings under the mode of pulse width modulation (PWM) as the study object, building a discrete mapping model of full-bridge circuit by stroboscopic sampling and conducting analyses on the bifurcation stability and chaotic characteristics based on this model built. It has established the adjustment range of proportional control coefficient and carrier cycle using numerical calculation, with the correctness of the theoretical analysis being verified by simulation and experimental results. Chaotic phenomena can be eliminated by reducing proportional coefficient of current controller and bus voltage, and increasing the carrier frequency, which enhances the stability of the three-level full-bridge converter.