Design and Control of a Multiphase Interleaving DC-DC Converter with Loss Optimizing Operating Strategies for Electric Vehicle

Abstract

The drivetrain components of commercial electric vehicles include the battery pack, inverter, and electric machine. However, in such a drivetrain configuration, the inverter input voltage (DC-Link voltage) is equal to the battery voltage, which presents some drawbacks. Firstly, different values are required to achieve the optimum voltage level during the battery stack and electric machine design process. Secondly, the battery state of charge negatively impacts the electric machine operating area. Additionally, as it will be demonstrated in this work, reducing the DC-Link voltage lowers inverter power losses. In operating points where the necessary machine voltage is lower than the battery voltage rated value, a fixed DC-Link voltage equal to the battery voltage results in additional inverter losses. The focus of this work is on the design and analysis of a battery electric vehicle drivetrain using an additional DC-DC converter extension in it. Accordingly, the main objective is to investigate the energy efficiency benefits of shifting the operating points of the drivetrain components by placing a DC-DC converter between the battery and the inverter-fed machine. For this purpose, a multiphase interleaving converter is selected, and through comprehensive modeling of the drivetrain, the appropriate control system is designed and evaluated on the one hand, and loss optimizing operating strategies are developed on the other hand to take the most advantage of the integration of a DC-DC converter into the drivetrain.