Efficiency Improvements from an Electric Vehicle Induction Motor Drive, with Augmentations to a PI Control

A novel induction motor drive system has been designed for electric vehicles. The drive's speed controller includes an augmented proportion-integration (PI) control which increases drive efficiency and enhances overload protection. The augmented PI speed control is simply a traditional PI control with signal paths additively influenced by two new signals. These two new signals force the PI control to not only track the reference speed, but also control the difference between the synchronous speed and rotor speed. The synchronous-to-rotor speed difference is influenced towards an optimal value for increased energy efficiency, and is limited, in the service of overload protection. The system was evaluated in transient simulation using a magnetic saturation motor model. The system tracked randomly generated signals, designed to mimic the time-varying input a driver would provide. Simulations, run with the efficiency augmentation turned off and turned on, showed a 2.8% increase in average efficiency. A localized time interval efficiency improvement of 4.6% was detected