Fractional Order PI Control of Dual Active Bridge Converter Using Generalized Average Modelling

Abstract

DC-DC converters are generally modeled using small-signal approximations considering small perturbations around a steady-state point. However, this is limited to a certain range of operation which in the presence of harmonic content in addition to dc offset might not provide an accurate result. Generalized Average modeling takes into account the harmonic contents along with the dc values and this can be used for alternating components such as inductor current in a Dual Active Bridge converter. The transfer function is derived which is an open-loop stable system, and in order to establish closed-loop stability, fractional order PI controller is used in this paper. Further, the optimization technique is applied in order to optimize the control variables as the degree of freedom has increased due to the incorporation of fractional powers. These optimized values are used to establish the closed-loop stable operation of a DAB converter and the technique is validated through MATLAB simulations. The entire results are shown in the figures with specifications tabulated and confirm the accurate setpoint tracking with the ripples in range.