Double Fed Induction Machine for All-wheel-drive Application in Electric Vehicles

Sammanfattning

AbstractThe transition to electric vehicles (EVs) demands innovative drivetrain solutions that maximize performance, reliability and reduces complexity and cost. This thesis deals with the modelling, novel strategy for controlling, and analysis of double-fed induction machines (DFIM) for an allwheel- drive scenario in electric vehicles and the integration of double-fed induction machines (DFIM) in electric all-wheel-drive (AWD) systems, aiming to maintain performance comparable to conventional systems using induction machines (IM) and permanent magnet synchronous machines (PMSM). The research addresses the challenge of reducing overall components in an electric AWD system by replacing the IM+PMSM combination with a DFIM+PMSM setup, utilising a single, compact micro-converter at the DFIM rotor, and controlling the PMSM and DFIM stator through a PMSM controller. The study begins by examining the fundamental principles of DFIMs, highlighting their dual stator and rotor winding configuration which allows for variable frequency control through power electronics. This unique characteristic facilitates bidirectional power flow and regenerative braking, key advantages for EV applications. The thesis then discusses the working of DFIMs into AWD systems, focusing on the requirements of power between the rotor and stator of the DFIM in order to provide deeper understanding into coordination of torque to improve handling and performance. Simulation models and experimental setups are utilized to analyse the performance of DFIMbased AWD systems under different driving conditions. Key performance indicators such as efficiency, response time, traction control, and energy consumption are evaluated and compared with traditional AWDs with induction motor as the front (auxiliary) drive and permanent magnet synchronous motor(PMSM) at the rear (primary) drive. The results indicate that DFIMs offer enhanced efficiency and torque control, while reducing the power electronics requirement significantly.This is achieved by powering both the DFIM stator and PMSM stator using the PMSM controller and exciting the DFIM rotor using a micro converter. Results demonstrated that the DFIM consumes minimal rotor power (up to 6 kW) in a 215 kW machine, suggesting its feasibility for AWD applications. The DFIM can operate in tandem with the PMSM in a 60-40 or 80-20 torque split, reducing losses associated with disengaging the DFIM. Furthermore, the thesis addresses the challenges of implementing DFIMs in AWD systems, including control complexity, and cost considerations. Estimation of DFIM machine parameters, robust control algorithms, and cost-effective drivetrain options are proposed as potential solutions to these challenges. In conclusion, DFIMs present a promising alternative for AWD systems in electric vehicles, offering significant benefits in terms of efficiency, performance, and control. The insights gained from this study could pave the way for the development of more advanced and efficient electric drivetrains, contributing to the broader adoption of electric vehicles and the advancement of sustainable transportation technologies.