High energy efficiency oriented-control and design of WFSM based on driving condition of electric vehicle

The purpose of this paper is to increase the energy efficiency of an electric vehicle (EV) with a wound-field synchronous motor (WFSM). Therefore, methods are proposed to estimate and improve the energy efficiency of the EV as well as the performance of the WFSM. The following contributions are provided: 1) EV model as well as the mathematical model of the electric motor are explained considering the common Artemis driving cycle (CADC); 2) a control method for maximizing the energy efficiency of the electric motor is proposed; 3) analysis methods for calculating the circuit parameters (resistance, inductance, and flux linkage) and losses (ohmic, iron, and mechanical loss) are described. The efficiency of the machine is accurately determined using the proposed analysis method; 4) based on the proposed methods, the design process of the WFSM is proposed to improve the energy efficiency considering the vehicle system and driving cycle; and 5) the proposed methods are verified through tests of the prototype and improved motor. As a result, through the proposed design and control method, even though the volume of the improved motor was 7.8% smaller than that of the prototype, the efficiency of the improved motor was higher than that of the prototype in all regions. In addition, to confirm the effectiveness of the proposed methods, the performance of the electric vehicle considering the driving cycle was analyzed according to the characteristics of the electric motor. The energy loss of the improved motor with the proposed control and design method was 63.3% less than that of the prototype. Accordingly, the energy efficiency of the vehicle system and the energy consumption of the battery increased by 7.8%p and decreased by 2.0 kWh, respectively.