DC-Voltage Control Design under Saturation Nonlinearity by Using Singular Perturbation Theory

This paper proposes a dc-voltage control design for a dc-dc converter with saturation nonlinearity. The suggested implementation is only slightly altered from the traditional structure of cascaded PI-controllers for handling the nonlinearity introduced by the input voltage limitation. Singular Perturbation Theory (SPT) is used to justify time-scale separation between the outer loop voltage control implementation and the inner loop current control. Furthermore, it is proved by SPT and Lyapunovs direct method that the proposed dc-voltage control system is globally asymptotically stable with input voltage saturation nonlinearity. Simulation results are presented to illustrate how the voltage saturation can influence a regular dc-voltage control loop and how the proposed implementation can ensure a stable and smooth response when reaching the saturation limit.