Link Current Optimization for Triple Port Active Bridge Converter with Series Voltage Injection

A Dual Active Bridge (DAB) converter is commonly used as an interface between energy storage systems and DC buses in applications such as distributed generation and electric vehicles. Various modulation schemes, like Single Phase-Shift (SPS), Dual Phase-Shift (DPS), and Triple Phase-Shift (TPS), are used in DAB operation. However, when the voltage conversion ratio deviates from unity, these schemes lead to a higher link current stress. Although modulation and optimization techniques can reduce this stress, they often limit the power range, prevent softswitching over a wide range, and result in moderate efficiency. To address these issues, a novel optimization scheme is proposed by injecting series voltage into the secondary side of the transformer through an auxiliary third port. This injection helps to reduce the link current stress in an optimized manner based on the available voltage at the auxiliary port. Optimization is achieved by adjusting power flow from the third port to minimize link current stress across different output power ranges. The proposed optimization method is verified through simulation and through experimental results from a scaled-down prototypes.