Research On Power Allocation For Multi Module Fuel Cell Hybrid Power System

Fuel cell is a clean and efficient power generation device,which can replace the traditional fossil fuels as the ideal power source of the automobile.However,due to the drawbacks of fuel cell such as its soft output characteristics,slow dynamic response and it is unable to recycle energy,fuel cells are usually required to cooperate with auxiliary energy storage equipment to form a hybrid power system in practical application.The traditional hybrid power system with only one fuel cell stack has some problems such as the low reliability and efficiency,in addition,the hybrid system also requires a reasonable power allocation strategy and control methods to further improve the overall efficiency and dynamic response speed,thus both the power and fuel economy issues can be taken into account.Firstly,the advantages and disadvantages of various energy forms of fuel cell hybrid power system are analyzed.On this basis,supercapacitor is selected as the auxiliary energy,the multi-module fuel cell system is used to replace the single fuel cell system as the main energy source of the system.Then kinds of connection structures between multiple fuel cells are introduced,and parallel connection between multiple fuel cells is chosen after comparing the structures.And then DC/DC converters for the hybrid system are designed,thus the overall topology of the hybrid system is determined.Secondly,aiming at the multi-module fuel cell hybrid power system,a power allocation strategy that can switch the working mode of the system is designed based on the analyses of traditional power distribution strategy for hybrid system and the power distribution between the multiple fuel cells,which can make the fuel cells work in the high efficiency area as much as possible.A PI controller is designed to verify the effectiveness of the power allocation strategy through a preliminary simulation analysis.The failure of fuel cells in the system and the treatment methods are stated,and the safe operation modes are designed to improve the reliability of the system.Then the passive control theory is used to design the controller for the system,the simulation combining with the passive controller and the power allocation strategy is carried out to analyze the state of the system in the working mode switching and the performance under the UDDS conditions,and to verify the improvement of the system dynamic response speed with the use of the passive controller and the performance of the power allocation strategy under complex conditionsFinally,the hardware-in-the-loop(HIL)simulation platform is built for the hybrid power system,and the simulations for UDDS condition and some other conditions are carried out on the platform to validate the applicability of the power allocation strategy under various working conditions,the speed and efficiency of simulation verification are greatly improved and the simulation results will be more close to the actual.The fuel consumption of the fuel cell system under various working conditions is analyzed,which verifies that the economy of the system is improved through the power distribution strategy.The results demonstrates that the application of the multi-module fuel cell hybrid system combining the power allocation strategy of switching working mode and the passive controller can greatly improve the efficiency,reliability and the dynamic response performance of the system,the vehicle power requirements can be meet and the economy of the system is also improved.