Research on control strategy of bidirectional energy storage converter for a certain type of export locomotive

Dual active bridge (DAB) converters are widely used in DC microgrids, fuel cells, electric vehicles, and other fields, due to their advantages of high power density, bi-directional energy flow, electrical isolation, and the ease of soft switching. However, their application in rail transit remains limited. This paper presents an innovative input-series output-parallel dual active bridge (ISOP-DAB) converter design based on single phase shift control, to address special requirements in rail transit scenarios featuring high voltage, high power, and modularization. The application of this converter design to an export locomotive model enables bi-directional energy flow between the power batteries and the traction DC busbars, and offers a targeted solution to achieve input voltage balancing and output current sharing for the ISOP-DAB configuration. The paper systematically analyzed the fundamental operating principles and power transfer characteristics of bidirectional energy storage converter under this control strategy. The introduction of a dynamic decoupling control algorithm allowed for achieving the dual-objective cooperative control of output voltage stabilization and module equilibrium. Results from simulations conducted using a MATLAB-based simulation model and type tests using complete cabinets including charge-discharge switching and dynamic load conditions validated the effectiveness and feasibility of the control strategy. The findings provide a theoretical foundation and engineering reference for the modular design of bidirectional energy storage converters in rail transit applications.