Research On DC/DC Converter Systems For Medium Voltage DC Distribution Network Based On SiC MOSFET

In order to adapt to the wide application of renewable energy and distributed energy,the DC power distribution system is considered to be one of the development directions of the power system.As the voltage conversion equipment in the medium voltage DC power distribution system,the DC/DC converter still has many scientific problems and challenges in how to efficiently and reliably realize this equipment,from the topology to the control method to the engineering application.The emergence of wide bandgap power devices has created conditions for the high frequency and miniaturization of DC/DC converters in medium voltage DC distribution networks.Benefiting from the characteristics of silicon carbide semiconductor materials,SiC MOSFET,as the mainstream silicon carbide power device,has many advantages in terms of switching speed,heat dissipation performance,and withstand voltage.This paper aims to solve the key problems of SiC MOSFET in the application of DC/DC converters in medium voltage DC distribution network,and has done an in-depth research in the aspects of SiC MOSFET device characteristics,converter topology and control strategy,principle prototype design and implementation.First of all,in order to realize the reliable application of SiC MOSFET,the static and dynamic characteristics of SiC MOSFET have been analyzed,the principle of dynamic characteristic test has been explained,the reason of voltage and current oscillation has been analyzed in combination with stray parameters,and the generation mechanism and suppression methods of crosstalk in the application of SiC MOSFET bas been analyzed in detail.Secondly,in view of the coupling problem of input and output voltage in the InputSeries Output-Parallel(ISOP)type Dual Active Bridge(DAB),a small signal circuit model of ISOP type DAB system has been established,the decoupling control method of input voltage equalization is derived,and the effectiveness of the decoupling control strategy has been verified by simulation.Finally,a 10 k V/400 V SiC MOSFET-based ISOP type DC/DC converter prototype has been designed,and the selection and design methods of the SiC MOSFET,filter capacitor,and isolation transformer in the prototype are described in detail.Combining the working principle of DAB converter,the loss model of SiC MOSFET has been derived,the loss bas been calculated and a reasonable heat sink has been selected.According to the switching characteristics of SiC MOSFET,the drive board bas been designed.Combined with the decoupling control strategy,the control system suitable for the prototype of this principle has been designed,and the reliability of the hardware platform design and the equalization control has been verified through experiments.This paper has 69 figures,4 tables,and 86 references.