Enhanced Load Step Response for a Bi-directional DC-DC Converter

An essential requirement for a high performance dual active bridge (DAB) DC-DC converter is to rapidly and accurately maintain its DC output voltage under all operating conditions. This paper uses a harmonic modeling strategy to create a linearised dynamic model of a DAB that accurately identifies its transient response to both a reference voltage change and an output load current change. Using this model, a feedforward compensation strategy is presented that significantly improves the DAB's transient response to an output load change. The transient performance is then further enhanced by analytically compensating for the non-linear deadtime distortion that is caused by the converter switching processes. The resultant control system achieves rapid and precise output voltage regulation for both reference voltage and output load changes. The theoretical analysis is confirmed by both matching simulation and experimental investigations.