Research On Energy Management Method Of Fuel Cell Hybrid Electric Vehicle Based On Minimum Principle

At present,human beings are at the historical moment where information technology and renewable energy meet,and an energy revolution in which renewable energy replaces the dominant position of fossil energy is undercurrent.Hydrogen energy as a clean secondary energy carrier is an important part of future energy changes,and fuel cells are the main application scenarios of hydrogen energy.In recent years,electric vehicles that use proton exchange membrane fuel cells as the power source have been extensively studied because of their advantages such as clean and efficient,long cruising range,and fast filling.However,the cost and durability of proton exchange membrane fuel cells are the main obstacles to their commercialization.Numerous studies have shown that the frequently changing operating conditions during vehicle operation are the main reasons for the decline of vehicle fuel cell life.The innovation of materials and the optimization of control strategies are effective methods to solve this problem.Adding auxiliary energy systems such as batteries and super capacitors to fuel cell vehicles can not only relieve the pressure on the fuel cell under dynamic operating conditions,but also absorb energy from the braking process of the vehicle,which can improve the durability and economy of fuel cell vehicles.Since fuel cell hybrid vehicles have multiple power sources,the focus of the control strategy is on the design of energy management strategies.The main works and contributions of this dissertation are as follows:1)Aiming at the problem of describing the behavior of the fuel cell system,a simplified model of the fuel cell system is established from the perspective of control.This simplification focuses on the establishment of the air-side model,which mainly relies on two assumptions:the gas in the cathode and anode are fully humidified,and water flooding is not considered;the anode-side pressure is equal to the cathode-side pressure.Simplifying the model makes the design of the internal controller of the fuel cell simple,and shortens the simulation time on the basis of ensuring the accuracy of the model.The simplified model is verified under dynamic current conditions.When the fuel cell system is well controlled,it demonstrated the rationality of using its static output curve to represent the fuel cell dynamic system in energy management.2)Aiming at the fuel cell hybrid vehicle energy management problem,a mathematical description of the energy optimization problem is established,and the Pontryagin's Minimum Principle is introduced to solve the optimization problem.In order to show that the Pontryagin's Minimum Principle under certain conditions is globally optimal,a dynamic programming algorithm is designed and compared with it.Taking into account the durability of the fuel cell,the fuel cell output power change rate limit is introduced,and the effect of the continuous and discontinuous form of the cost function on the fuel cell output power distribution is analyzed.3)Aiming at the problem of online application of the minimum principle,an adaptive energy management strategy combining the minimum principle and speed prediction is proposed,and its adaptability is reflected in the update of co-state variables.In order to improve the accuracy of speed prediction,a Markov chain speed predictor based on "classification+prediction" is proposed considering the existing speed prediction technology,and the effectiveness of the proposed method is verified in different driving modes.For driving pattern recognition,the application of support vector machine in driving pattern recognition is studied,and particle swarm optimization algorithm is used to optimize it.