Research On Energy Management Strategy Of Hydrogen Fuel Cell Hybrid Power System

In order to solve the increasingly serious energy shortage and environmental pollution problems,the development of efficient and pollution-free clean energy has become an urgent issue for all countries in the world.Among all kinds of clean energy sources,hydrogen fuel cell is gradually becoming an international research hotspot with its high energy density,no emission and high efficiency.As a specific application of hydrogen fuel cell hybrid power system,it has been developed in the field of urban buses and other public transportation.Most of the traditional hydrogen fuel cell hybrid power system energy management strategies only consider the power and economy of the system,but do not fully consider the working condition-sensitive operating characteristics of hydrogen fuel cells.In this thesis,we mainly focus on hydrogen fuel cell hybrid power system city buses to study the energy distribution strategy to make the output power fluctuation of hydrogen fuel cell more smoothly,and the main work is as follows.Firstly,several common hybrid power system topologies are analyzed,based on which a vehicle dynamics model is designed according to the relevant parameters of the city bus.The power demand of this model is calculated under three extreme working conditions,namely full-load maximum speed cruising,full-load maximum climbing operation and maximum acceleration,and the maximum value of the three is taken to ensure its dynamics meets the requirements.Combining the operating characteristics of the hydrogen fuel cell and lithium battery,the parameter configuration of the system energy source is determined,and the preliminary parameters of the DC/DC converter are calculated on this basis.According to the working principle of key components in the hydrogen fuel cell hybrid power system,the simulation models of hydrogen fuel cell,lithium battery,Boost boost converter and bidirectional DC/DC converter are built in Matlab/Simulink,and the rationality of each module is verified separately.Then the city bus simulation model is built in AVL/Cruise for converting the standard cycle operating conditions into power demand data and verifying that its dynamics meets the design requirements.In order to improve the service life of hydrogen fuel cell in hybrid power system,this thesis innovatively applies the idea of digital signal processing to power demand splitting from the operating characteristics of hydrogen fuel cell,and proposes an adaptive improved low-pass filtering strategy based on the idea of frequency separation.The core lies in designing a low-pass filtering algorithm so that the hydrogen fuel cell provides low-frequency fluctuating power and main energy output,and the lithium battery provides high-frequency fluctuating power and recovered braking energy.To this end,the filtering effects of the sliding average filtering method,FFT filtering method and Savitzky-Golay filtering method under actual driving conditions are studied respectively,and based on these,an adaptive improved low-pass filtering algorithm based on SavitzkyGolay filtering method and FFT filtering method is proposed.To verify the rationality and effectiveness of the strategy in this thesis,a control model based on rule control is built and compared with the strategy in this thesis under the driving conditions of a Chinese city bus and the actual conditions of a city bus,respectively.Finally,the effectiveness of this thesis’ s strategy is verified in terms of lithium battery SOC stability,hydrogen fuel cell power smoothness and hydrogen fuel cell remaining life.