Charge-based ZVS modulation of a 3–5 level bidirectional dual active bridge DC-DC converter

This paper presents a charge-based Zero Voltage Switching (ZVS) modulation strategy for the 3 Level–5 Level (3–5L) Dual Active Bridge (DAB) DC-DC converter. The DAB combines a primary-side full bridge and a secondary-side mixed bridge (i.e. a 3-level T-type leg with a half-bridge leg), linked by a high-frequency transformer and an inductor. A ZVS modulation strategy is presented, in which a charge-based model of the non-linear parasitic output capacitances of the switches is used to accurately describe the ZVS constraints. Moreover, commutation inductances are included to extend the ZVS region to the entire operating range. The configuration of the secondary-side bridge facilitates increased flexibility compared to a full bridge configuration, in order to reduce the RMS current in the switches, inductor, and transformer. The nominal power of the investigated converter is 2.8 kW with input voltage range from 8 V to 16 V and output voltage range from 175 V to 450 V. The RMS currents of the 3–5L DAB are compared with those of a typical 3–3L DAB, applying the proposed modulation strategy in the 3–5L DAB, and a similar strategy previously proposed in literature in the 3–3L DAB.