PSO-Based Optimization of DC-Link Current Harmonics in Traction VSI for an Electric Vehicle

A large number of modern electric traction vehicles are equipped with drive systems based on induction motors fed by voltage source inverters (VSIs). This solution is known to be a significant source of interfering disturbances for a railway signaling system. Therefore, the amplitudes of current harmonics generated by railway vehicles should meet the required limits. This article presents an optimization technique developed to control dc-link current harmonics generated by a VSI traction drive. The purpose of this article is to develop an optimization procedure to determine a switching strategy for VSI to keep the dc-link current harmonics below limits established for railway applications. The procedure presented in this article combines a particle swarm optimization algorithm and an analytical frequency-domain approach for the calculation of dc-link current harmonics. Moreover, the minimization of low-order torque harmonics is added to the optimization process as well. For calculations of dc-link current harmonics, the convolution of VSI output current and voltage harmonics is utilized and described. The modulation technique computed by the proposed optimization procedure is applied to a laboratory-scale VSI drive. Finally, the validity of theoretical consideration is confirmed by comparing the analytical results with laboratory measurements. The proposed optimization technique is suitable to determine a switching strategy for application in railway vehicles supplied with dc traction systems.