Discontinuous Control Strategy for Loss Reduction in Wound-Field Synchronous Machine Based Electric Vehicle Powertrain System

Research towards increasing the powertrain system efficiency in battery electric vehicles is crucial for increasing vehicle range or decreasing battery requirements and reducing total cost of ownership (TCO). The pulse and glide (PnG) method is a discontinuous torque control strategy that decreases eDrive energy consumption via a software based approach for rare–earth–free electric motor powertrain systems. The proposed method increases system efficiency by repeatedly accelerating the vehicle at peak efficiency operating regions of the powertrain and allowing the vehicle to coast rather than applying a constant torque command. In this paper, a vehicle model is developed to determine the forces acting on the vehicle to dictate torque requirements of the system and to analyze the acceleration and speed profiles of the proposed PnG torque pulses. A baseline wound field synchronous machine (WFSM) and IGBT based inverter is utilized to evaluate the percentage reduction in system energy consumption due to the PnG control strategy. An optimal approach to select PnG duty cycle and pulse period is proposed to maximize energy savings while maintaining acceptable levels of speed variation in a fixed vehicle speed operating condition. A novel jerk limitation controller methodology is introduced to mitigate user discomfort due to the modulated torque profile. The framework is employed to determine the percentage reduction in energy consumption attainable across the speed range of the powertrain system and to generate look up tables of region based PnG duty cycle and pulse period for control implementation.