Optimized Modular Design of Neutral-Point-Clamped Traction Inverters for Multiple Electric Vehicles

Traction inverters play a crucial role in the growing industry of electric vehicles. On the one hand, the traction inverter design is quite challenging and needs to pursue key design goals including high efficiency, high reliability, high power density, and low weight and cost. On the other hand, a modular and scalable design methodology to cover a wide range of vehicles is highly desirable. This article explores the optimal or near-optimal design configuration of the multilevel neutral-point-clamped legs of traction inverters for three use cases: an electric motorcycle, an electric passenger car, and an electric truck. The design is based on the use of an array of switching cells. The optimal configuration and operation of the switching cells are obtained through a weighted objective function in terms of efficiency, reliability, and simplicity. The design optimization results illustrate the modularity, scalability, and suitability of the used design approach, where a single module fits all applications, and the available degrees of freedom enable the adaptation of the design to the application and operating conditions, to maximize its efficiency and reliability.