Optimal DC-Link Voltage Mapping for SiC-Based EV Drives: Considering the Impact of a Synchronous Boost Converter

This paper seeks to identify an optimal DC-link voltage across the complete range of drive operating conditions utilizing a loss minimization approach by integrating a DC-DC converter into the powertrain, thereby enhancing powertrain efficiency. This involves a comprehensive analysis of power losses in a connected silicon carbide (SiC)-based converter-inverter system, incorporating temperature variations, alongside a finite element method (FEM) analysis of losses in an Interior Permanent Magnet (IPM) synchronous machine, accounting for variable DC-link voltages. The results are then compared with those of traditional silicon-insulated-gate bipolar transistor (Si-IGBT) systems. The findings reveal that including a DC-DC converter into a powertrain, and adjusting the optimum DC-link voltages, is advantageous, particularly for low battery terminal voltages. Consequently, the powertrain system, incorporating a DC-DC boost converter, exhibits lower total loss values, with a difference of up to 5 kW loss difference for high-speed, low-torque regions compared to the case when not incorporating the DC-DC converter. Furthermore, applying the proposed optimal DC-link profile in the Worldwide harmonized Light vehicle Test Cycle (WLTC) leads to a reduction of up to 16% in accumulated energy losses in the SiC driveline compared to its IGBT counterpart. In addition, applying the optimal DC-link profile reduces energy losses by 58% in the SiC-based system and by 54% in the IGBT-based system, compared to operating with a fixed 300 V DC-bus voltage.