Suppression of dc‐offset current in ac‐link of dual‐active‐bridge dc‐dc converter based on triple‐phase‐shift optimal control

Abstract

Abstract When dual‐active‐bridge dc‐dc converter (DAB) with energy storage load operates in a wide voltage range and high dynamic condition, the mismatch of primary and secondary side voltages will lead to high current stress and loss, and the dc‐offset current in the high‐frequency ac link will lead to magnetic saturation of magnetic components, which will damage the devices in serious cases. Therefore, aiming at the operation of DAB in a wide voltage range, a triple‐phase‐shift (TPS) optimal control strategy is adopted, and the phase shift angles of the bridges are adjusted according to the voltage ratio, so as to optimize the electrical stress and loss. What is more, the cause and mechanism of dc‐offset current in the ac‐link are analysed. Based on the TPS optimal strategy, the static dc‐offset current is suppressed with the low‐bandwidth detection of the offset current and the dynamic dc‐offset current is suppressed with the planning the current trajectory. A small‐power prototype is built, and the effectiveness of the TPS optimal control and the static and dynamic dc‐offset current suppression is verified.

Keywords

• DC‐DC power convertors
• dynamic response
• high‐frequency transformers
• optical control