Active Power Decoupling using Zero-Sequence Inductance of Three-Phase Transformer

Abstract:
Electric Vehicle (EV) On-Board Chargers (OBCs) are designed to deliver power from the grid to the battery, typically rated in kilowatts, requiring high power density and reliability. Traditional OBCs utilize bulky dc link capacitors to filter double-line (DL) frequency power ripple from the ac input, while active power decoupling (APD) is an alternative to mitigate ripple effects and increase power density. This paper proposes an APD circuit integrated into a three-phase (TP) dual active bridge (DAB) converter with a TP transformer, serving as the dc-dc stage of EV OBCs. The topology is analyzed and verified for a 400 V battery charging system, demonstrating the potential of a 36% capacitor volume saving with a 0.56% efficiency penalty at 8 kW.