Second life potential of electric vehicle power electronics for more circular economies

As newer generations of electric vehicles get to market, more electric vehicles with out-of-use components will emerge. Some of these electric vehicles will have components that no longer pass automotive standards. This study establishes a method of assessing the second life potential of end-of-life traction power converters repurposed for stationary applications like solar energy conversion systems. Traction converters in electric vehicles are subject to aggressive mission profiles as the vehicle can go from idle to full power acceleration and surge power conditions within seconds. Hence, these traction converters experience electrothermal stress profiles that degrade the electrical and thermal impedance of the modules thereby reducing the efficiency. The converters are considered unusable after the electrical and thermal impedance of the module increases by at least 20 %, which ideally should occur after the vehicles useable life. However, with suitable de-rating in less stressful stationary applications, end-of-life traction converters could still be capable of high efficiency and reliable performance. Using electrothermal simulations and reliability modelling, this study demonstrates that a 300 kW traction inverter with 20 %, 40 %, 60 % higher thermal and electrical impedance (corresponding to 1.6, 3.4, 5.5 % reduced efficiency in vehicle drivetrains) is capable of higher than 98.5 % efficiency when used as a solar inverter for micro-grid applications. A method of estimating power module lifetime consumption in the second life application has been proposed indicating that demand side management is critical for maximizing the second life of the converter if vehicle charging is integrated into the photovoltaic powered micro-grid.