Three-Phase Interleaved Bidirectional <i>LLC</i> Resonant Converter With Vertically Integrated Magnetics for Energy Storage System Applications

The bidirectional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter is increasingly adopted in energy storage systems due to its notable attributes such as high efficiency, high power density, and low electromagnetic interference (EMI). To extend output power and minimize current ripple, a common strategy is paralleling multiple-phase interleaved converters, which has been proved to offer superior efficiency and power density. This article introduces a three-phase interleaved bidirectional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter with vertically integrated magnetics. By integrating transformers and inductors through a shared magnetic plate, the volume of magnetics is reduced. This configuration enables flux cancellation in both forward and backward operation modes, leading to reduced core loss and enhanced converter efficiency. The proposed reluctance model is employed to analyze the impact of zero-sequence magnetic flux and magnetizing current. Through an optimal design procedure, a 400 V/48 V 3.5 kW prototype is implemented, achieving a peak efficiency of 98.6% and California Energy Commission (CEC) efficiencies of 98.32% and 98.25% for forward and backward operation modes, respectively. The prototype also reaches a power density of 500 W/in<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>.