Analytical Modelling and Control of Dual Active Bridge Converter Considering all Phase-Shifts

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Abstract
The Dual Active Bridge (DAB) is one of the most promising topologies among bidirectional isolated DC-DC converters, especially in interfaces to batteries. It is recently gaining interest due to its versatile features. The investigative studies are progressing to inspect, control and improve the overall performance of the DAB converter. Currently, there are challenges regarding the control of DAB. It has complex nonlinear properties and also has to attain multiple aims (e.g. regulating power flow, achieving zero voltage switching (ZVS) and minimizing current stresses).This has resulted in the requirement to investigate with different abstraction levels in DAB design process, e.g. ideal behavior (steady-state, dynamics), losses analysis, optimization of parameters and control. In this paper, an accurate analytical model is presented which makes the design of voltage controller simple and independent of the operating conditions. The analytical developments presented, based on the superposition principle, allow obtaining the waveforms of inductor and output current using a simple and fast closed-form procedure. This allows to apply optimization methods for the selection of the operating point or during the design stage (e.g. for selecting inductance and frequency values). Moreover, the novel fully analytical model describes the output current vs. phase-shifts relation. As a study-case, the Single Phase-Shift (SPS) is used for regulating the output current (average) in an open-loop control (by linearizing the control of DAB output voltage. Simulations in PLECS Blockset validate the theoretical results.

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