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Summary
With the advancement of automobile electrification, smart charging infrastructure is rapidly popularizing, and the application of V2G vehicles inside the smart grid to the grid is also in the ascendant. More and more application fields require active frontend power converters with bidirectional current conversion functions. This article analyzes the application performance of SiC power MOSFETs in highfrequency PFC converters in typical threephase power applications, and proves the advantages of silicon carbide power solutions. For example, the threephase twolevel fullbridge (B6) converter and The NPC2 threelevel (3LTType) converter is used as a research case, and the output power and switching frequency are compared with silicon power semiconductors.
Preface
With the advancement of automobile electrification, smart charging infrastructure is rapidly popularizing, and the application of V2G vehicles inside the smart grid to the grid is also in the ascendant. More and more application fields require active frontend power converters with bidirectional current conversion functions. This article analyzes the application performance of SiC power MOSFETs in highfrequency PFC converters in typical threephase power applications, and proves the advantages of silicon carbide power solutions.
SiC MOSFET in active frontend bidirectional converter
The choice of power converter topology is closely related to the availability of semiconductor technology. The recently introduced silicon carbide (SiC) active switching technology, namely SiC MOSFET, expands the power conversion topology to applications with higher switching frequencies. Figure 1 shows the relationship between typical technology and power size and switching frequency. The application field of SiC devices is quite extensive, and with the development of technology and the optimization of production cost, its application scope is still expanding.
Figure 1 Technology and application positioning map
This paper evaluates the relationship between energy efficiency and switching frequency of typical threephase twolevel fullbridge (B6) and NPC2 threelevel (3LTType) bidirectional power converters using two different power semiconductor technologies: siliconbased IGBT and SiC MOSFET .
Figure 2 Twolevel full bridge (B6) and NPC2 threelevel (3LTT) bidirectional PFC converter based on SiC MOSFET
Use the formula listed in Table 1 to calculate the power loss of the twolevel converter, including conduction loss and switching loss. The calculation formula takes into account the modulation index M=Vac/(Vdc/2) and the phase angle between the input voltage and current that determines the working mode of the bidirectional converter. The characteristic data of the switching loss is the basic parameter, which can be obtained from the data sheet, and according to the considered output voltage Vdc and the switching current IL, the scaling factor of the switching energy value is considered.The power consumption calculation of the threelevel Tconverter requires a special formula^{[2]}, Will be discussed in the final paper.
Table 1: Power loss calculation formula
Twolevel converter 

Conduction loss 
Switching loss 
The calculation process has considered the specifications of the power converter listed in Table 2 and the power Electronic devices used in the Circuit of Figure 2 listed in Table 3. The conduction loss and switching loss of the two converters, as well as the semiconductor energy efficiency and As a function of switching frequency. Considering that the converter has two modes: rectifier and inverter, the switching frequency range is set between 10kHz and 100kHz. The evaluation results are shown in Figure 3 and Figure 4. Observing the results of energy efficiency evaluation, it is not difficult to find that as the switching frequency increases, the advantage of SiC MOSFET is significantly higher than that of siliconbased IGBT. In the twolevel fullbridge topology, the energy efficiency gap between the two at 100kHz is as high as 10%. The final version of the paper will be Comprehensive discussion. Finally, in order to verify the calculation results, a configurable test platform was developed, as shown in Figure 5. The test results will be listed in the final version of the paper.
Table 2 Power converter specifications
Table 3 Characteristics of power devices
Figure 3 The relationship between the power loss and energy efficiency of a twolevel power converter and the switching frequency: IGBT vs SiC MOSFET
Figure 4 The relationship between power loss, energy efficiency and switching frequency of a threelevel 3LTT power converter: IGBT vs SiC MOSFET
Figure 5Schematic and physical diagram of the prototype of the test platform
in conclusion
This article evaluates the topological structure of highpower PFC and introduces the performance of SiC MOSFETs in highfrequency and highvoltage applications. Especially, in twolevel converters, the advantages of SiC MOSFETs compared with IGBTs are more obvious, because the maximum output DC voltage of highfrequency switching requires semiconductor devices with higher breakdown voltage, which has an adverse effect on energy efficiency. At the same time, the energy efficiency is reduced by as much as 10%.
references
[1] JW Kolar and T. Friedli, “The Essence of ThreePhase PFC Rectifier Systems—Part I,” in IEEE Transactions on Power Electronics, vol. 28, no. 1, pp. 176198, Jan. 2013, doi: 10.1109 /TPEL.2012.2197867.
[2] M. Schweizer, T. Friedli, and JW Kolar “Comparative Evaluation of Advanced ThreePhase ThreeLevel Inverter/Converter Topologies Against TwoLevel Systems. IEEE Transactions on Industrial Electronics. 60. 5515 5527. 10.1109/TIE.2012.2233698.
[3] Datasheet STGW25H120DF2, STMicroelectronics;
[4] Datasheet STGB30H60DFB, STMicroelectronics;
[5] Datasheet SCTW40N120, STMicroelectronics;
[6] Datasheet SCTW35N65G2V, STMicroelectronics.
Keywords: MOSFET IGBT
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