Study Of The Input-Series-Output-Parallel Multiple Full SiC Phase-Shifted Full-Bridge ZVS Converter

The urban rail vehicle auxiliary power system is the core component of the urban rail metro,and its performance determines the operational safety and operational efficiency of the vehicle.As the main part of the auxiliary power supply,the DC/DC converter is developing in the direction of high frequency,high efficiency,high power density,light weight and miniaturization.The feasibility of applying the commercial 1700V all SiC power module to DC 1500V power supply DC auxiliary converter is studied.The circuit topology of the input-series-output-parallel(ISOP)phase-shifted full-bridge(PSFB)ZVS converter is selected.The optimized interleaved voltage equalization control strategy is used.The computer simulation and hardware platform experiments are used to test and analyze the all SiC ISOP PSFB converter.The operating characteristics of the circuit are compared with the Si IGBT auxiliary power converter for loss characteristics,which verifies the correctness and feasibility of the scheme.Firstly,the different circuit topologies applicable to the auxiliary power converter is analyzed.The detailed working principle of the ISOP PSFB converter is studied.The soft-switching implementation and dead time selection,duty cycle loss,rectifier diode oscillation,voltage and current equalization are studied.Among them,three suppression methods are proposed for diode oscillation.The simulation comparison analysis is carried out with PSIM.The results show that the diode clamp method is more suitable for the converter.Secondly,the control strategy and the mathematical model of ISOP PSFB converter is studied.The corresponding transfer function is solved.The common duty cycle control strategy is studied.A control index showing the average flow degree is proposed to improve the common duty cycle mode.The simulation is verified by PSIM simulation.An improved interleaved voltage equalization control strategy is proposed.The controller is designed with a double closed loop design method.It is verified by MATLAB simulation.A loss comparison analysis was performed on IGBT type and all SiC type converters that meet the requirements of auxiliary power supply.At last,a digital control system and a hardware experiment platform that meet the performance indicators are designed.The soft-start experiment results show that the converter can ensure the safety.The open-loop experiment shows that the theoretical analysis is correct.The results of the diode clamp experiment reduce the secondary side oscillation;the interleaving control experiment shows that the method can reduce the output current ripple.The closed-loop verification experiment shows it can reach the output voltage regulation,output current sharing and input voltage equalization control target.