Analysis Of DAB With Design And Experimental Research Of SiC Prototype

Isolated bi-directional DC-DC converters are widely applied in electric vehicles,aerospace and distributed generation,especially in fast developed DC micro-networks,the demand for isolated high-power DC-DC converters with higher voltage is increasing more and more.This paper choose the dual active bridge(DAB)as isolated bi-directional DC-DC converters,it has the advantages of high efficiency,high power density and so on.Compare to LLC converter which use the resonant way the DAB system is suitable for higher power transmission,moreover the new generation semiconductor material SiC device isapplied to design DAB converter prototype.Through the experiment,research and test advantages of SiC device for the effect of system performance improvement.Firstly,the research status and development trend of dual active bridge converter are studied and summarized.A general discussion of the characteristic of SiC device and Si device and the usability of SiC device apply on DAB has been done.At the present stage commercial SiC device have more Switching loss than Si device,system design still needs soft switching mode to avoid excessive switching losses,and make full use of the advantage of low conducting losses of SiC device.So the working principle of dual active bridge converter based on phase shift control is expounded,the transmission principle of the converter and the realization of soft switch are analyzed,and the theoretical analysis is verified by simulation.Then,a dual active bridge converter system is modeled,the average and small signal models of the system are derived,based on the small signal model,the transfer function of the system is obtained.Uses the obtained transfer function of DAB converter,a system performance of dual active bridge converter is analyzed,and based on the characteristics of the system,a dual-loop controller composed of the output voltage and the inductor current is designed.The rationality of controller design is verified by simulation.The following part of this paper expounds the principle of interleaving,analyze the advantages implementation scheme and control method of double active bridge converter with interleaving use in the high power applications,and verified by simulation.The second part of this paper is design of a prototype system with 10 kW bidirectional 800 V DAB converter use the SiC device.Based on the device selection of system design,a fair analysis method of dual active bridge system efficiency based on SiC and Si devices is proposed,it proves that SiC has improved the efficiency of the system.Hardware design including power device,filter parameters,high frequency transformer,inductance,SiC Mosfet driver circuit,signal sampling and conditioning circuit.Reducing the effect of parasitic parameters on EMI by rational design.Finally,according to the design plan,the prototype of dual active bridge converter is completed.The open loop and closed loop dynamic performance test and efficiency test were carried out.The theoretical analysis of dual active bridge converter and the rationality of hardware design are checked.