On the robust linear control of the “buck-buck” converter: An active disturbance rejection approach

In this article, the cascade connection of two “buck” converters is examined from the perspective of differential flatness and Generalized Proportional Integral (GPI) observer-based control. The multi-variable nonlinear “buck-buck” converter is subject to unknown, time-varying, load current demands, at each one of the outputs of the two constitutive stages. The linear output feedback controllers have to actively counteract the uncertain exogenous load demands as well as the surprisingly highly nonlinear endogenous interactions, arising between the converters, due to their cascade connection. Illustrative simulation results are presented.