Input-output linearization and stabilization analysis of internal dynamics of buck-boost converters

Using the state-space average modeling method, a nonlinear affine model of Buck-Boost converter is set up. Based on the input-output linearization method of differential geometry theory, the internal dynamics of the systems, with output represented by inductor current and capacitor voltage respectively, are been studied. It is pointed out that the average PWM model of the `Buck-Boost' converter, with output represented by the average capacitor voltage, is actually a nonminimum phase system, and its internal dynamics is unstable. So, it is unfeasible to control the output voltage directly. But, if the output is represented by the average inductor current, the system is a minimum phase system, and its internal dynamics is asymptotically stable. It is feasible to control the output voltage indirect through the regulation of inductor current. Further, the nonlinear state feedback law is proposed. The control law proposed in this paper has some advantages of being simple, easy to implement. The validity of the indirect output capacitor voltage control scheme using input-output feedback linearization method is verified by numerical simulation results. Key waveforms based on simulated extensive work verify the superiority of the proposed nonlinear control method.