Modeling and Design of Three-Phase Interleaved Buck Converter Based on Differential Flatness Theory

This paper addresses the issues of large output fluctuation and long recovery time in three-phase interleaved Buck converters under traditional PI control when subjected to external interference. A modeling and design scheme for three-phase interleaved Buck converters is proposed based on differential flatness theory. The output capacitor voltage is selected as the flat output variable for the voltage outer loop, and the duty cycle of the switching tubes is used as the control variable for the current inner loop. Firstly, the state-space model of the converter is established. Through differential flatness coordinate transformation, the differential flatness mathematical model of the three-phase interleaved Buck converter is obtained. To ensure that the error between the output variable and the state variable approaches zero and the error integral is sufficiently small, the voltage outer loop and current inner loop are designed using Barbalat’s lemma and Lyapunov’s theorem. Finally, a simulation experimental system is built to compare the dynamic response characteristics of threephase interleaved Buck converters with differential flatness control and PI control, verifying the correctness and feasibility of the theoretical analysis.