Research On Dual-active-bridge DC/DC Converter For Solid State Transformer

In recent years,the power system has developed rapidly,its scale has been continuously expanded,the voltage level has been continuously increased,and the types of loads have become increasingly diversified.Due to the limitations of its own functions,traditional transformers cannot meet the challenges brought by modern power grids.At this time,solid-state transformers come into being.The three-stage structure of solid-state transformers usually includes the rectifier stage,isolation stage and inverter stage.This paper mainly deals with the isolation stage,dual-active DC-DC converter.This paper studies and analyzes the topology of dual-active DC-DC converter and the switching modes of the dual-active DC-DC converter in the two types of typical control modes: single-phase shift and double-phase shift in the single-side.The capacitor voltage on the load side is selected as the state variable,the small signal mathematical model of the dual-active DC-DC converter is deduced,based on which the voltage closed-loop control system is designed,and the correctness of the closed-loop system design is verified through simulation;A new control strategy of equalizing current based on real-time current deviation is proposed for the current balance problem of multiple dual-active bridge modules,which is based on real-time current deviation control.The principle is simple,easy to implement and with high accuracy.According to the quantity relationship of steady-state of the dual-active DC-DC converter,the parameters of the key components such as the switch tube in the power circuit are calculated and determined;various parameters of the high-frequency transformer are analyzed and calculated to complete the design and manufacture of the high-frequency transformer;the control link with the core of the TMS320F28335 type DSP is designed.Experiments on the double-active DC-DC converter with single-side dual phase-shift control were conducted through experimental prototypes.The experimental waveforms and data collected are consistent with the theoretical analysis,the functions of the dual-active DC-DC converter and the feasibility and correctness of its control strategy are verified.