Bidirectional power flow in energy storage facilities is common and required. Energy supply from energy storages and energy imbursement back to the storages and preferably at high-efficiency are basic operations for these kinds of equipment. Since the boom growth on uninterruptable power supplies for critical loads and electric vehicles, storages, especially batteries, are in deep demands nowadays. Although high-efficient bidirectional power flow can be achieved by two unilateral dc-dc converters, an integrated bidirectional converter will benefit with compact size and more efficient equipment usage. In this paper, a full-bridge isolated converter with an auxiliary inductor can reach zero-current-switching in current-fed step-up mode; and zero-voltage-switching in voltage-fed step-down mode. The test results have a good agreement with theoretical waveforms under suitable control strategies. At step-up mode, conversion efficiency can be up to 95%; while at step-down mode, conversion efficiency reaches 94%.

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