PI controller design via singular perturbation technique for AC-AC buck-boost converter

The problem of AC voltage regulation based on AC-AC buck-boost converter is discussed in presence of resistor load variations and voltage source variations as well. The design methodology of cascaded proportional-integral (PI) controller via singular perturbation technique is presented where two-time-scale motions are artificially induced in the closed-loop system. Stability conditions imposed on the fast and slow modes and sufficiently large mode separation rate can ensure that the full-order closed-loop system achieves the desired properties in such a way that the desired output voltage is maintained. The existence of stable limit cycle in the fast motion subsystem gives the robustness of the output voltage value in the presence of the resistor load variations and amplitude of voltage source variations. The method of singular perturbations is used throughout the paper. Numerical simulations for AC-AC buck-boost converter are presented.