Wide Bandgap Power Device-based Current Source Inverter for Electric Traction Application

As is well known in the literature, the use of wide bandgap (WBG)power devices in power conversion units enables higher switching frequencies and lower conduction losses to be achieved, improving their efficiency and power density. Drives used for electric traction are fed by a two-level voltage source inverter (VSI) with a switching frequency not exceeding 30kHz to limit overvoltages at the motor terminals, which can degrade the winding insulation and bearings. The main objective of this research activity is to investigate an alternative solution to VSI-fed drives by using a Current Source Inverter (CSI) based on WBG power devices. The CSI provides a near-sinusoidal output voltage with a significant reduction in dv/dt, thus increasing the motor drive's reliability and improving electromagnetic interference (EMI) immunity. In particular, the working principle of a CSI for electric traction applications is analysed in this paper, and the main strengths and technical challenges are identified and supported by simulations based on Spice model devices and experimental tests. The preliminary simulation results underline that the CSI topology offers significant improvements at high switching frequencies compared to the VSI due to the filtering action provided by suitably combining the design of the dc-link inductor and filter capacitors. Furthermore, the final presentation will include a design analysis of passive elements. The experimental results obtained from tests conducted on a 2kVA test bench will also be presented.