A multi-active bridge power electronic transformer and its soft start method

Abstract

The invention relates to the technical field of DC distribution and utilization, and aims to provide a multi-active bridge power electronic transformer and a soft start method thereof. The auxiliary power supply and soft-start strategy are used to precharge the output side port capacitance, so that the port voltage basically reaches the rated value, and then the transformer is smoothed by switching the control mode during the process of cutting off the auxiliary power supply and connecting the distributed power supply. Enter steady state control mode. There are three degrees of freedom in the multi-mode control strategy, which respectively control the magnitude and direction of the transmission power from the high-voltage port to the medium-low voltage port. The invention can ensure the stable start of the port voltage, and at the same time, the precharging implemented from the high voltage side can successfully limit the peak value of the inductance current, and avoid the occurrence of system impact current. A variety of control modes only need to use PI controllers, the control method is simple, and the continuity of the output after mode switching can be guaranteed.

Description

technical field [0001] The invention relates to a multi-active bridge power electronic transformer and a soft start method thereof, belonging to the technical field of direct current distribution and utilization. Background technique [0002] Due to its high efficiency, controllability and other advantages, DC distribution network has gradually attracted widespread attention. Among them, the multi-voltage level DC distribution network can be compatible with distributed sources, storage and loads of different voltage levels, which is conducive to further exerting the advantages of the DC distribution network. [0003] The multi-voltage level DC distribution network includes multiple DC buses of different voltage levels, and the interconnection of multi-voltage levels is usually realized through DC / DC power electronic transformers to transform voltage. At present, DC / DC power electronic transformers can be divided into isolated type and non-isolated type, among which isolated...

AI Technical Summary

Problems solved by technology

The above soft-start strategy research is mainly aimed at the situation that the dual-active-bridge power electronic transformer starts from the high-voltage side, and the multi-active-bridge power electronic transformer has port coupling, so the problem of limiting the current during the start-up process is more complicated, and the corresponding Start-up strategies are less researched

If the low-voltage side supports the high-voltage side control mode, the existing method also starts charging from the low-voltage side, resulting in excessive capacitor current

To solve this problem, the present invention proposes a multi-active bridge power electronic transformer and its soft start method, which solves the current impact problem when the low-voltage side supports the high-voltage side through multi-mode switching

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