Energy Efficiency Improvement via Bus Voltage Control of Inverter for Electric Vehicles

Although great effort has been devoted with various approaches on the improvement in energy efficiency of electric vehicles, much of the focus has been on the design of electric devices and power electronic systems and of energy storage systems with energy management strategies. This paper proposes a bus voltage control method that actively and dynamically controls the bus voltage applied to the inverter through a dc/dc converter, such that it tracks the rotational speed of the motor, that aimed to improve the energy efficiency of the inverter, or the overall energy efficiency of power electronic systems. A detailed energy efficiency model is first developed that takes into account the inverter loss and motor iron loss. Some detailed and in-depth analyses on energy efficiency have been conducted that conclude that the inverter's energy efficiency is largely related to the voltage applied, and the voltage is further closely related to the rotational speed of the motor. Simulations and in-vehicle experiments under a New European Driving Cycle (NEDC) have been conducted that demonstrate the effectiveness of the proposed method on the improvement in energy efficiency of the inverter, as well as the system as a whole.