A new method for AC traction drive frequency characteristic measurement

This paper deals with the description of a new method for ac traction drives frequency characteristic measurement. The proposed method helps to find dangerous resonant frequencies of the traction drive (especially of the input LC filter on dc electrification system) and to propose corrections mitigating those oscillations. The proposed method has been verified by simulations and experiment on two different types of ac drives: (i) at an induction machine drive with open loop scalar control and (ii) at a surface mounted permanent magnet synchronous motor drive controlled by a DTC algorithm. The results show that DTC controlled drive in constant taken power mode amplifies capacitor voltage oscillations, therefore; a solution has been proposed to protect the drive against those oscillations. This voltage oscillation mitigation proposal has been experimentally verified on a laboratory model of the PMSM traction drive with rated power of 10.7 kW.