Investigating the dynamics of a buck converter with time-delay feedback control

Abstract

The paper deals with the dynamics features of a closed automatic control system based on a buck converter with a function to control nonlinear dynamic processes. A comprehensive analysis of the system under study is carried out using both small-signal average dynamic models and nonlinear dynamic models. For the first time, a small-signal average model of a system with a control function for nonlinear dynamic processes based on a time-delay feedback control has been obtained. The influence of this control method on Bode plots of an open system is shown. It is noted that the use of the time-delay feedback control ensures the stability of both the equilibrium point of the small-signal average model and the fixed point of the periodic mode of the nonlinear dynamic model of the system under consideration. This enables to achieve high quality output voltage. The application of the time-delay feedback control does not require to correct the system parameters, which ensures a given speed and low losses in the power switch of the converter. In addition, the quality of the transition process in the system is improved, namely, oscillation is eliminated and overshoot is reduced. Using the time-delay feedback control, it is possible to provide the desired dynamic mode in the areas of instability of the initial system without controlling nonlinear dynamic processes, which makes it possible to increase the speed due to the small time constant of the regulator. These results were obtained for the first time and can be used in the design of pulse power supply systems of a wide variety.