Improved Fourier Domain Model and Adaptive Controller Design for Handling Double Resonance Impact on Performance of Current-Fed Isolated DC/DC Converter

Interleaved current fed dual active bridge (CFDAB) converter is a potential converter for low voltage battery charging applications. The output inductors, which are present on the low voltage side of CFDAB, provide ripple-free battery current and shoot through protection under fault conditions. The behavior of this converter slightly differs from the voltage fed dual active bridge (VFDAB) converter and is less studied in literature. This paper presents the study in two parts. Firstly, an improved Fourier domain model of CFDAB is presented which can seamlessly incorporate numerous harmonics for better large signal model accuracy unlike conventional generalized average modeling (GAM) technique. Furthermore, the small signal model is constructed for selective dominant harmonics in order to preserve simplicity. The presented Fourier domain model is based on Harmonic state space (HSS) model. Secondly, it discusses the presence of two resonances in the small signal model of CFDAB. One of them lies at switching frequency while other lies at converter natural frequency. The latter resonance either increases the steady state ripple or decreases the bandwidth of the conventional closed loop current controller. Hence, this paper also presents adaptive notch integrated PI controller in order to overcome above drawbacks of simple PI controller. Simulations are carried out in MATLAB/Simulink. Experimental investigations are carried out on a laboratory prototype. Simulation and experimental results confirm the plausibility of the model and controller.