Small-Signal Discrete-time Modeling and Digital Control of the Bi-directional DC/DC Converters

Bi-directional DC/DC converters have been widely used in many applications because of its energy bidirectional flow. This paper proposes the small-signal discrete-time model of bi-directional buck/boost converter at a selected operating point and the accuracy of the model is verified in comparison to the traditional continuous-time average model. Also, the digital PI controller is designed for the converter based on the discrete-time model. In addition, a unified digital current controller is utilized and suitable for two working modes. A set of effective digital PI voltage controller parameters are also designed. Simulation results of the bi-directional buck/boost converter under start-up condition and load transient condition in MATLAB are presented. Finally, two hardware testing platforms are employed and the experimental results are presented to validate the proposed methods.