Research On Wide Range Input Bidirectional DC/DC Converter

The rail transit train is powered by the traction power supply system of urban rail transit.In case of an accident in the power supply system,the DC traction power supply network cannot provide electric energy to the rail transit train.The bidirectional DC /DC converter(BDC)with wide input range can be applied to this unexpected situation.The input-series output-parallel(ISOP)combined converter is suitable for high voltage input and low voltage output.The Buck / Boost-CLLLC two-stage bidirectional DC /DC converter is suitable for medium and high power applications with large input voltage fluctuation range and bidirectional power flow.This paper mainly studies the ISOP system with Buck / Boost-CLLLC two-stage bidirectional DC / DC converter as a single module.In this paper,the principle of Buck / Boost-CLLLC two-stage bidirectional DC /DC converter is analyzed,and the parameters of ISOP system are designed.The small signal modeling of the Buck / Boost-CLLLC two-stage bidirectional DC / DC converter is carried out.The small signal modeling of the bidirectional Buck / Boost converter is derived according to the state space average method.The mall signal modeling of the bidirectional CLLLC converter is derived according to the first harmonic method.By simplifying it,the third order small signal model is derived,and the expressions of input voltage to output voltage transfer function and input impedance of the bidirectional CLLLC converter are obtained.In this paper,the control system of Buck / Boost-CLLLC two-stage bidirectional DC / DC converter is designed,and the bidirectional DC / DC converter adopts the double closed-loop control strategy of voltage and current.Both the voltage loop and the current loop controller adopt the proportional-integral(PI)controller.The PI controller not only has good robustness,but also can make the control system respond to the output error quickly and realize the tracking of the output value without static error.Finally,the simulation model of ISOP system and a 10 k W Buck / Boost-CLLLC two-stage bidirectional DC / DC converter are built in the laboratory to verify.The simulation results and experimental results are consistent with the theoretical analysis,which proves the correctness of the theoretical analysis.There are 78 pictures,10 tables and 50 references.