Research On Real-time Optimization Strategy Of Multi-stack Fuel Cell System Based On Incremental Contro

As an important carrier of hydrogen energy power generation,the proton exchange membrane fuel cell（PEMFC）system is environment-friendly and has the advantage of operating at normal temperature,which can meet the requirements of"carbon peak"and"carbon neutralization"medium and long-term energy development planning.And it has been widely used in electric vehicles,urban rail transit and public transportation and many other fields.However,a single large PEMFC system cannot meet the high-power requirements of urban rail transit nowadays and has the disadvantage of insufficient reliability.Therefore,the use of multi-stack or modular fuel cell system（MFCS）has gained more attraction in new energy power generation of rail transit.However,the difference in efficiency characteristics between different fuel cell systems（FCS）will seriously affect the overall energy efficiency of MFCS,therefore a reasonable energy management strategy is the key to improving the fuel economy and durability of MFCS.Therefore,this paper mainly studies the modeling of PEMFC system and its energy management strategy,and the main work is as follows:Firstly,the 30k W PEMFC system named FCVelo City-MD30^?is analyzed and modeled,and the influence of the power characteristics of each auxiliary system and PEMFC module on the hydrogen consumption characteristics of the PEMFC system is analyzed in detail because the auxiliary systems such as air compressor,hydrogen recirculation blower,water pump and heat exchanger have critical influence on the hydrogen consumption characteristics of the PEMFC system,and then the overall modeling of the single-stack PEMFC system is constructed.Then,an MFCS model consisting of three PEMFC systems was established based on the single-stack PEMFC system model.Secondly,this paper proposes an increment-oriented online power distribution strategy for MFCS,which is based on the quadratic polynomial formulation derived from the hydrogen consumption analysis of integrated fuel cell system and takes the optimal efficiency and durability as the objective function.And the function approximation is realized by using the polynomial function which realizes the dynamic programming abstract description of the problem,and the optimal solution is obtained by using the Lagrange multiplier method.The quantitative correlation between fuel economy and durability in MFCS is obtained with comprehensively considering the hydrogen consumption characteristics and performance differences between different PEMFC systems,and the demand power is reasonably distributed according to the performance of each PEMFC system.An iterative high-order sliding-mode differentiation procedure is used in the initial condition determination to improve the strategy applicability with fault tolerance.Besides,performance-dominated power limits are considered in the global switching sequence calculation.The online collaborative performance improvement between MFCS fuel economy and durability is achieved.Finally,the effectiveness and practicability of the proposed strategy are verified by three designed scenario cases with fault tolerance operation performance,one-cycle short-term and life-cycle long-term evaluations.Simulation results demonstrate that the proposed strategy can guarantee fault tolerance operation and collaborative performance enhancement for multi-stack fuel cell systems with minimum hydrogen consumption and maximum service life compared with other three advanced strategies.