A Zero-Voltage Switching Three-Port Isolated Full-Bridge Converter

Abstract

This paper proposes an integrated single-stage three-port DC-DC converter. The proposed converter interfaces two bidirectional source/storage ports, and a galvanically isolated loading port. The power topology is based on the integration of a bi-phase boost pre-regulator stage into a phase-shift controlled full-bridge converter. The four bridge switches play the combined role of realizing synchronous boost conversion, and driving the transformer. The proposed topology is conditionally able to achieve zero-voltage switching of all bridge switches. Compared to the cascaded converter approach, this topology alleviates the cost overhead associated with introducing a switching leg for boost operation, and saves the switching loss it would exhibit. A constant-frequency switching scheme is adopted that presents two degrees of freedom necessary for proper control. The duty-cycle of the two phase-legs of the bridge is varied to control energy flow in the boost section, while the relative phase-shift between the legs is utilized to regulate the power pushed to the loading port. The operation of the topology is verified using an experimental 1 kW prototype, designed to handle a photovoltaic source, a storage battery bank, and a regulated DC load