Nonlinear feedback regulator design for the Cuk converter

The method of extended linearization is used for designing stabilizing nonlinear proportional-integral (PI) feedback controllers which regulate to a constant set-point value either the average output inductor current, the average input inductor current, or the average transfer capacitor voltage of a pulse width modulation (PWM) controlled Cuk converter. The design is carried out on the basis of the frequency-domain Ziegler-Nichols method, applied to a family of transfer function models of the linearized average PWM controlled circuit, parametrized by constant operating equilibrium points