Functional Situational Awareness for Reliable and Efficient Operation of Hybrid Electric Vehicle Power Systems

Abstract

Hybrid electric vehicle power systems (VPSs) comprise of limited energy resources and variable load requirements. The functional status of components and subsystems that make up the VPS is critical to the overall system operation. The degradation and critical operating states of components affect system efficiency and reliability differently. Therefore, monitoring of the functional status (referred to as functional situational awareness (FSA)) of components, subsystems and system is needed for reliable and efficient operation of VPS. In this study, VPS-FSA is inferred hierarchically at three levels of complexity, namely, at the component, subsystem and system level. In each of these levels, two types of FSA are inferred to qualify and quantify the functional states of components, subsystems and system. Component-FSA is based on currents and temperatures measurements of the components. Subsystem-FSA and System-FSA are derived as fusion of Component-FSA and Subsystem-FSA, respectively. Type 1-FSA is inferred using reasoning and threshold values. Type 2-FSA is derived using more complex relationships of temperature and current states. Typical FSA results are presented for a VPS for a standard drive cycle and long-term effects on the VPS operation are shown over several drive cylces.INDEX TERMS Functional situational awareness, hybrid electric vehicles power system, component degradation, critical operating states. NOMENCLATURE y Type 2-Degradation FSA of y