Design of a three-level inverter for an electric vehicle.
Thesis DisciplineElectrical Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
A conventional two-level BIT inverter was installed in an electric vehicle to control two AC induction motors at the University of Canterbury. Nowadays, power device technology has made tremendous progress, and the IGBT becomes the best device in high-quality drive system with inverters in the mid power range. A new three-phase, three-level IGBT inverter has been design and will replace the conventional inverter for the electric vehicle. This inverter produces an output voltage waveform which has three difference levels and can generate a more sinusoidal shape than that of convention two-level inverters. The output voltage of a three-level inverter contains less harmonics than that of a conventional inverter. This thesis deals with the development and implementation of a three-phase, three-level IGBT inverter for an electric vehicle. The inverter design incorporated a laminated busbar structure to reduce stray inductance. An IGBT gate drive circuit with two-stage protection in the inverter is developed. To improve the efficiency and reliability of the inverter, the gate drive provides high speed switching with attention to di/dt and dv/dt requirements and controlled two-stage fault protection. Computer Simulations are performed to demonstrate the operation of a three-level inverter and to determine its specifications. Experimental tests are carried out to evaluate the performance of the three-level inverter as an AC induction motor speed controller. The inverter is tested on a motor load at full voltage, and maximum rated current and torque. Simulation and experimental results show that in principle a three-level inverter is suitable for the propulsion system of an electric vehicle.