Inverter losses minimization using variable switching frequency based on multi-objective optimization

This article presents the result of an VSI-losses minimization technique based on multi-objective convex optimization for a salient-pole PMSM with a two-level VSI for an automotive application. The optimization, using the switching frequency as control variable, is based on a multi-objective cost function defined by the combination of VSI-losses and electromagnetic torque peak-peak ripple, analytically expressed using time-domain current predictions. The optimization target is to keep an optimum balance between VSI-losses and electromagnetic torque ripple, using variable switching frequency (VSF). The primary objective with this article is the presented design methodology. Simulations are used to verify functionality as well as influence of different scaling factors. In addition, the NEDC driving cycle is used to further quantify the results for two different cost function setups.