Large-Signal Stability for DAB Converters Feeding Constant Power Load based on State Trajectory Analysis

Different from resistive loads, constant power loads (CPLs) may threaten the stability of power interfaces (PIs) due to the negative incremental impedance. As one of the promising PIs, dual active bridge (DAB) converters have received widespread attention. However, the large-signal stability criteria of DAB converters under CPLs remain challenging. To fill this gap, this paper thoroughly explores the inherent stability mechanism by analyzing the state trajectory of the DAB converter for the first time. Sufficient conditions for the large-signal stability of the closed-loop controlled DAB converter under CPLs are specified. Based on the derived trajectory operation criteria of DAB converters, an advanced boundary control in the geometrical domain is proposed to guarantee the large-signal stability of DAB converters feeding CPLs. Main design considerations and recommendations are given. Experimental results show that the proposed strategy can reduce the start-up transient time by 50% and speed up the output-voltage-reference-change transient time by over 30% compared to the traditional control while ensuring a stable operation of DAB converters under CPLs.