DC-Link RMS Current Reduction by Increasing Paralleled Three-Phase Inverter Module Number for Segmented Traction Drive

This paper presents a three-phase inverter dc-link capacitor root-mean-square (RMS) current reduction method. The proposed method is especially suitable for high current electric drive applications while multiple switching devices have to be connected in parallel at the package level, such as Toyota Camry or Tesla Model S. This paper analyzed the proposed method theoretically using double Fourier analysis, and derived the optimal operating point. Furthermore, the effectiveness of the proposed method is also verified by simulation under different PWM strategies (SPWM, SVPWM, and DPWM1), carrier shapes (triangle and sawtooth), and power factors. The proposed dc-link capacitor current cancellation method could lead to smaller dc-link capacitor design; the system volume reduction and cost are also estimated with different number of device packages in parallel. The experimental results are also provided using a 6 kW SiC-based inverter prototype assuming three paralleled devices in each phase leg, which are consistent with the theoretical analysis and simulation results.