Effects of Target Modulation Index on Variable DC Voltage Control for Electric Powertrains in Medium Duty Delivery Trucks

A potentially efficient topology for electric vehicle powertrains consists of a two-level inverter with a DC-DC converter, operated with variable DC voltage control. Previous studies show that variable DC voltage control can lower the amount of motor torque ripple and increase the efficiency of a drive system as a whole. In literature, the target Modulation Index (MI) is assumed to be kept at a high value. The effect of the target MI on the overall efficiency of an electric vehicle was studied via simulation in this paper using a class 4 delivery truck as a test vehicle. Various duty cycles were used to compare the efficiency effects. According to the results, a MI between 1.1 and 1.5 should be targeted in most cases.