Mathematical Approach for Computational Analysis of Triple Active Bridge DC–DC Converters in Hybrid Energy Storage Applications

Abstract

Hybrid energy storage systems need to have high efficiency bi-directional power converters to manage power exchanges between batteries, supercapacitors and also the DC bus under dynamically varying operating conditions. Traditional converter analysis approaches depend on simplified circuit models which are not able to capture the nonlinear interactions between the converter ports leading to the loss of prediction accuracy for power transfer, voltage regulation and efficiency. This study presents a mathematical prediction model in the form of a nonlinear state-space representation of a Triple Active Bridge (TAB) DC–DC converter with the inclusion of the phase-shift characteristics of the power transfer equations and solved numerically using MATLAB/Simulink based simulation. The proposed framework is able to comprehensively assess the converter dynamics of multiple modes such as charging, discharging and bidirectional energy transfer. According to the simulation results, the proposed mathematical framework is effective in hybrid energy storage applications with peak conversion efficiency of 97.8%, the negative/positive regulation of the DC-link voltage within ±1.2%, the prediction error of the power transfer below 2.0%, and a ripple of 14.6% less than conventional analytical model for current.