Nonlinear Geometric Control of Current-Fed Dual-Active Bridge Converter With Direct Power Transfer

Linear controllers impose many limitations on the performance of DC–DC converters. Typically, the dynamics of these converters are averaged over a switching cycle and then linearized to create a Linear Time-Invariant (LTI) system model, which is subsequently used to design a linear controller. However, this linear approximation of nonlinear systems around a single operating point, combined with averaging, often leads to sub-optimal performance, particularly in applications with a wide range of operating conditions. This paper presents a novel nonlinear geometric-based SO(2) controller for bidirectional DC–DC converters. The proposed controller can directly control the high-frequency current and steer the system trajectory on a surface of a torus to achieve fast dynamics and improved stability. This paper presents the mathematical foundations and analysis, and demonstrates the superior performance of the proposed controller through simulations and experiments.