Research on Semiconductor Losses of Three-Phase Inverter for Traction Drive Considering Different Pulse Width Modulation Strategies
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Date
2025-10
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Addis Ababa University
Abstract
Electric traction systems are essential to the global move toward sustainable and energy efficient transportation, especially in the railway sector. At the center of these systems are three-phase inverters, which convert direct current (DC) into alternating current (AC) to power traction motors. The performance of these inverters largely depends on the semiconductor devices used. Si-IGBTs are commonly used due to their affordability and robust performance. However, they suffer from high conduction and switching losses, particularly at higher switching frequencies, which limits efficiency and increases thermal stress. Therefore, it is important to develop a realistic loss estimation model for power semiconductors to overcome the limitations of device-specific commercial tools. Accurately modeling and estimating these losses is critical to understanding their impact on thermal behavior, efficiency, and the lifespan of the inverter. nIn this thesis, conduction and switching losses in Si-IGBTs, free-wheeling diodes (FWDs), and SiC-MOSFETs are modeled using a common analytical model applicable to both Space Vector PWM (SVPWM) and Sinusoidal PWM (SPWM). The model combines a piecewise linear approximation for switching losses with a conduction loss model based on an equivalent thirdorder harmonic approximation of the duty cycle. Unlike commercial tools that are typically limited to specific device types, the developed model supports a broad range of semiconductor devices, enabling consistent and comparative loss evaluation. Validation of the proposed model is conducted using MATLAB/Simulink and PLECS and compared with commercial tools i.e. Semikron’s SemiSel-V5 and Infineon’s CIPM. The model is closely matches, and in some cases surpasses, commercial tools in accuracy. SiC-MOSFET based inverters achieve 98.22% system efficiency, compared to 91.76% for Si-IGBT-based inverters, reflecting significant reductions in conduction and switching losses. Comparison with commercial tools shows minimal deviations: for the Infineon module, conduction and switching losses differ by less than 0.5%. In conclusion, this research developed a versatile loss estimation model that outperforms commercial tools in accuracy and flexibility. As results confirm that SiC-MOSFETs deliver significantly higher efficiency than Si-IGBTs, making them the preferred solution for high power
traction applications.
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Keywords
Semiconductor losses, Si-IGBT, SiC-MOSFET, freewheeling diode (FWD), Space Vector PWM (SVPWM), Sinusoidal PWM (SPWM), traction inverters, electric drives, permanent magnet synchronous motor (PMSM), thermal management