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.