A Traction Inverter Design for Increasing the DC Link Voltage in Electric Vehicles

Abstract

Using a high-voltage DC link in electric vehicles (EVs) can bring such benefits as higher power density, less weight, smaller components, less loss and heat, and faster charging, etc. The paper proposed a cost-effective high-efficiency four-switch three-phase (FSTP) traction inverter design to enable high DC link voltage in EVs. A comprehensive theoretical study on the control of FSTP inverters has been presented in comparison with six-switch three-phase (SSTP) inverters. The simplified Space Vector Pulse Width Modulation (SVPWM) control strategy proposed for FSTP inverters significantly reduces the complexity and computation burden of the control system and makes it easier to implement SVPWM FSTP inverters than SVPWM SSTP inverters. MATLAB Simscape models with switching loss correction are used to simulate and compare different solutions. The results from the case study demonstrate that the silicon (Si) FSTP inverter is 33.3% lower in cost and has 32.3% less power loss, as well as better THD compared to the Si SSTP inverter when transforming an EV powertrain from 400 V to 800 V. A silicon carbide (SiC) version of the FSTP inverter is also investigated for further efficiency improvement. It has been shown that another 21.7% of power saving can be achieved at a 12% higher cost of the Si SSTP inverter. Thus, the FSTP topology can help overcome the cost barrier of SiC technology and promote its adoption in EVs.