Ripple-Current Suppression in Two-Phase Interleaved Bidirectional Buck/Boost Converters Using Auxiliary Converter

Conventional two-phase interleaved bidirectional buck/boost converters (IBBCs) exhibit duty-dependent low-side current ripple despite 180° interleaving. This paper investigates an auxiliary bidirectional buck/boost converter (ABBC) connected across the same DC buses to suppress this residual ripple at selected operating conditions. The auxiliary branch uses two switches and one inductor, operates at twice the main switching frequency, and follows an explicit duty-dependent phase schedule. A complete switching-interval analysis gives continuous, periodic current waveforms and closed-form peak-to-peak ripple expressions for equal inductances and ideal continuous conduction. The analysis identifies a lower ripple than the conventional converter over 0.2 < D < 0.4 and 0.6 < D < 0.8; continuous auxiliary switching does not improve the ripple near D = 0.5. The experiments on a prototype rated at 1 kW use main and auxiliary switching frequencies of 40 and 80 kHz. The measured low-side ripple decreases by 70.1% and 79.5% at nominal forward duties of 0.30 and 0.65, respectively, and by 59.5% at a nominal reverse duty of 0.70. These results demonstrate low-side current-ripple reduction at the three tested operating conditions.