Active Power Sharing Control in Asymmetrical Bidirectional DC/DC Converter

In many practical applications, such as electric vehicle charging and smart transformers, reverse power flow is significantly lower than forward power flow. Designing a full-rated bidirectional DC/DC converter in such cases leads to increased hardware costs. To address this, recent research has explored isolated topologies that support asymmetrical bidirectional power flow at reduced cost. This manuscript investigates an asymmetrical bidirectional DC/DC (AB-DC/DC) converter that integrates a partial-scale active bridge and a partial-scale diode bridge connected in parallel on the secondary side. Passive power sharing between these bridges is controlled by selecting appropriate coupling inductors, but practical magnetic tolerances cause power imbalances. To mitigate this, a novel modulation technique is proposed to enable active power sharing, allowing power transfer from the diode bridge to the active bridge. The study covers various operating regions, including discontinuous conduction mode (DCM), continuous conduction mode (CCM), dual-active-bridge (DAB) mode, and two hybrid regions, where the diode bridge operates in DCM and the active bridge in CCM. Closed-form power expressions and boundary conditions are derived for all modes. The proposed strategy is validated through simulations and experimental measurements on a hardware prototype, demonstrating consistent waveform behavior and confirming the feasibility of active power transfer from the diode bridge to the active bridge.