Willans Line-Based Equivalent Consumption Minimization Strategy for Charge-Sustaining Hybrid Electric Vehicle

Energy management strategies for charge-sustaining hybrid electric vehicles reduce fuel consumption and maintain battery pack state of charge while meeting driver output power demand. The equivalent consumption minimization strategy is a real-time energy management strategy that makes use of an equivalence ratio to quantify electric power consumption in terms of fuel power consumption. The magnitude of the equivalence ratio determines the hybrid electric vehicle mode of operation and influences the ability of the energy management strategy to reduce fuel consumption as well as maintain the battery pack state of charge. The equivalent consumption minimization strategy in this article uses three Willans line models, which have an associated marginal efficiency and constant offset, to model the performance in the hybrid electric vehicle controller. The three Willans line models are linearly combined to generate a single static equivalence ratio that quantifies the fuel power-to-battery power conversion process for all hybrid electric vehicle modes of operation. A proportional-integral controller and polynomial penalty term are added to the static equivalence ratio to account for variations in the battery pack state of charge to maintain the battery pack state of charge. The Willans line-based equivalent consumption minimization strategy reduces fuel consumption while achieving charge-sustaining performance over city and highway drive cycles with a single static equivalence ratio and one set of controller gains.