Considering the limited driving range and inconvenient energy replenishment way of battery electric vehicle, fuel cell electric vehicles (FC EVs) are taken as a promising way to meet the requirements for long-distance low-carbon driving. However, due to the limitation of FC power ability, a battery is usually adopted as the supplement power source to fill the gap between the requirement of driving and the serviceability of FC. In consequence, energy management is essential and crucial to an efficient power flow to the wheel. In this paper, a self-optimizing power matching strategy is proposed, considering the energy efficiency and battery degradation, via implementing a deep deterministic policy gradient. Based on the proposed strategy, less energy consumption and longer FC and battery life can be expected in FC EV powertrain with optimal hybridization degree.

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Series hybrid electric buses with power follower control strategy require rotational speed of engine to operate over a wide range which may cause severe torsional vibration of generator set. In order to optimize operating domain of generator set for series hybrid electric bus, nonlinear dynamic model of generator set is established considering electromagnetic torque fluctuations. Then operating domain of generator set is optimized. Experimental results show that range of optimized rotational speed is 1500 < n < 5730, the range of optimized electromagnetic torque is 350 < T < 530.

Irregular internal excitation (engine excitation and motor excitation) and external excitation (road excitation) can cause torsional vibration which even leads to the break of shaft of parallel hybrid electric vehicle (HEV) powertrain. Moreover, the current energy management control strategy ignores the significance of torsional stability of HEV powertrain when formulates the operating domain. The objective of this paper is to optimize the control strategy of parallel hybrid electric vehicle with multiple excitation sources to improve the torsional stability. To achieve the goal, the simplified two-mass nonlinear dynamic model of HEV powertrain is established. Then we apply the nonlinear dynamics to predict the torsional instability range of HEV powertrain. The theoretical analytical results are used to instruct to optimize the control strategy. Finally we set up the experimental platform and perform the experiment to verify the optimization of control strategy. The experimental results show that the HEV powertrain experience torsional instability under current control strategy. The critical speed when the operation mode of HEV switches from electric driving mode to hybrid driving mode was optimized to vc = 16km/h. The operating domain of engine was optimized to 1670 < n1 < 1850rpm under hybrid driving mode and driving and charging mode. The results reveals that optimization of control strategy can improve torsional stability of HEV powertrain effectively.

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