Implementation of an Adjustable Target Modulation Index for a Variable DC Voltage Control in an Electric Delivery Truck

This paper introduces an alternative control strategy for the variable voltage control of an electric drivetrain for a Class 4 medium-duty delivery truck and compares the resulting vehicle energy consumption over standardized drive cycles. The baseline system, S1, uses a standard electric drivetrain without a DC-DC and a battery at 460 V. The proposed system, S2, contains a DC-DC converter and a lower voltage battery with three voltage options being investigated: 200 V, 230 V, and 300 V. Previous work has shown that using a bi-directional DC-DC converter, the Fixed Target Modulation Index (FTMI) of the power electronics can be optimized in order to reduce the energy consumption across a drive cycle. In this study an Adjustable Target Modulation Index (ATMI) is proposed, which combines the best aspects of the fixed target modulation index control to attempt to improve efficiency even further. The new control strategy is shown to improve the energy consumption by up to 2.34% over a vehicle with a conventional electric drivetrain, depending on the required drive cycle.