Emerging Developments in Fault-Tolerant Powertrain Topologies for Series Hybrid Electric Vehicle Motors

Abstract

The technological advancement of battery and fuel cell systems accelerated the development of plug-in Hybrid Electric Vehicles and Battery Electric Vehicles. Notably, hybridization can effectively extend the driving range and reduce refueling frequency. However, for a Highway-capable Plug-in Hybrid Electric Vehicle that interfaces with a power grid, the propulsion unit should be featured with function redundancy in order to minimize driving inconvenience. Motor and power converter constitute the core component of the electric propulsion unit. Consequently, faults can hindrance not only propulsion but also ancillary functions like charging/discharging operation and as a result degrade the overall mobility of the vehicle. With a focus on series HEV powertrain architectures, this study identifies the state of the art of current fault-tolerant design approaches enlightening both research and industry. A design process philosophy is proposed that consists of different levels of redundancy, where a higher level provides a higher reliability but at the cost of lower availability. Availability and reliability are two aspects of fault-tolerant design. Availability is often defined as the percentage of time in service. Reliability can be defined as the robustness to faults and it is related to the redundancy of the system, which can be maintained even without the service of a certain component. At least two main levels of redundancy can be considered for electric motor drives: (i) redundancy within the motor, inverter and controller, and (ii) redundancy across components in the propulsion circuit.