Development of PMP-based power management strategy for a parallel hybrid electric bus

To operate a hybrid electric vehicle efficiently, it is important how to manage energy components such as the engine, motor and battery of the vehicle. In this paper, the Pontryagin’s minimum principle (PMP) based power management strategy is developed and applied to a forward simulation program able to calculate the fuel economy of a vehicle with its specified driving cycle. Typical two other power management strategies, the Max state of charge (SOC) power management strategy and the power split ratio rule-based power management strategy are also developed and applied to verify the application possibility of the PMP-based power management strategy. A simulated comparison of the power management strategies using six driving cycles is conducted. As a result, considering the characteristics of buses which drive a routine cycle repeatedly, the PMP-based power management strategy, which shows the most efficient performance with respect to the fuel economy and the maintenance of the battery SOC, is more appropriate than the other power management strategies while the application of PMP-based power management strategy to a conventional vehicle has a difficulty because of the problem about maintenance of the battery SOC.