Fractional-order modeling and nonlinear dynamics analysis of voltage mode controlled flyback converter

To accurately investigate the nonlinear dynamic characteristics of a flyback converter, a fractional-order state-space averaged model of a voltage mode controlled flyback converter in continuous conduction mode is established based on fractional calculus theory. And low-frequency bifurcation maps which use PI controller parameters and reference voltage as bifurcation parameters are obtained. The low-frequency oscillation phenomenon is analyzed and compared with that of an integral-order flyback converter. The results show that under certain operating conditions, the fractional-order flyback converter exhibits low-frequency oscillations as certain circuit and control parameters change. Under the same circuit conditions, there is a difference in the stable parameter region between the fractional and integral-order models of the flyback converter. The stable zone of the fractional-order flyback converter is larger than that of the integral-order one. Therefore, the circuit is more difficult to enter a low-frequency oscillation state. The stability domain of low-frequency oscillations can be accurately predicted by using the small signal model of the fractional-order flyback converter. Finally, by performing circuit simulations and hardware-in-the-loop experiments, the rationality and correctness of the theoretical analysis are verified.