Advantages of using SiC MOSFETs in industrial high frequency bidirectional PFC power converters

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 front-end power converters with bidirectional current conversion functions. This article analyzes the application performance of SiC power MOSFETs in high-frequency PFC converters in typical three-phase power applications, and proves the advantages of silicon carbide power solutions. For example, the three-phase two-level full-bridge (B6) converter and The NPC2 three-level (3L-TType) 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 front-end power converters with bidirectional current conversion functions. This article analyzes the application performance of SiC power MOSFETs in high-frequency PFC converters in typical three-phase power applications, and proves the advantages of silicon carbide power solutions.

SiC MOSFET in active front-end 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.

This paper evaluates the relationship between energy efficiency and switching frequency of typical three-phase two-level full-bridge (B6) and NPC2 three-level (3L-TType) bidirectional power converters using two different power semiconductor technologies: silicon-based IGBT and SiC MOSFET .

Figure 2 Two-level full bridge (B6) and NPC2 three-level (3L-TT) bidirectional PFC converter based on SiC MOSFET

Use the formula listed in Table 1 to calculate the power loss of the two-level 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 three-level T-converter requires a special formula^[2], Will be discussed in the final paper.

Table 1: Power loss calculation formula

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 silicon-based IGBT. In the two-level full-bridge 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.

in conclusion

This article evaluates the topological structure of high-power PFC and introduces the performance of SiC MOSFETs in high-frequency and high-voltage applications. Especially, in two-level converters, the advantages of SiC MOSFETs compared with IGBTs are more obvious, because the maximum output DC voltage of high-frequency 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 Three-Phase PFC Rectifier Systems—Part I,” in IEEE Transactions on Power electronics, vol. 28, no. 1, pp. 176-198, Jan. 2013, doi: 10.1109 /TPEL.2012.2197867.

[2] M. Schweizer, T. Friedli, and JW Kolar “Comparative Evaluation of Advanced Three-Phase Three-Level Inverter/Converter Topologies Against Two-Level 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.