Ström- och spänningsripplets påverkan på DC-ledet i ett elfordon. Verifikation av teoretiska resultat genom mätningar.

Abstract

This thesis work examines the current and voltage ripple present in the DC link when an induction machine is powered by a battery source through a three phase inverter. The project evaluates the ripple at different frequencies that is generated due to the combined working principles of the induction machine and the switching of the inverter transistor. An available electrochemical impedance spectroscopy measurement of one battery cell identical to the type used in this project is used in a computer model to simulate and verify the ripple components against the measurement results from the physical model. The measurements show that sigificant levels of ripple in DC link voltage and current are present. Frequency analyses of the resulting waveforms show that the sixth harmonic component as well as multiples of the inverter switching frequency and their sidebands dominate the ripple waveforms. Simulations of DC link voltage and current ripple show that the characteristics and magnitude of the measured ripple components can be verified, however, with some deviation. A possible cause for deviation is due to the fact that some unknown impedances present in the physical battery system could not be measured and therefore are not represented in the computer model.