全局与瞬时特性兼优的燃料电池有轨电车能量管理策略

Management Strategy for Fuel Cell Trams with Both Global and Transient Characteristics

传统庞特里亚金极小值原理在应用到燃料电池混合动力有轨电车的能量管理时,由于需要已知未来工况条件,存在实时性与工况适应性差的问题。为此,该文提出一种全局优化与实时工况构建相结合的应对策略。首先,基于极小值原理,以氢耗量最小为目标,在保证负载需求与避免超级电容SOC大范围波动的约束下,求取燃料电池全局最优参考输出功率;其次,将电车运行过程划分为怠速牵引、加速启动、稳速行驶、减速制动和再生制动五种模式,并分别根据各自运行特性构建状态转移概率矩阵,进而以燃料电池效率为判据确定工作模式并更新瞬时最优功率;最后,分别在有轨电车典型和非典型行驶工况中,对该文所提策略、传统极小值原理策略及等效氢耗最小策略进行在线运行对比分析。结果表明,该文所提策略能够提升混合动力系统应对高功率负载突变鲁棒性,有效降低燃料电池启停次数,实现全局和实时最优功率分配。

The Pontryagin minimal principle(PMP)strategy,a widely used global optimization strategy,requires to know all working conditions in advance for energy management of the hybrid system of fuel cell trams.However,the actual operation of the tram is characterized by strong randomness and fluctuation,resulting in poor real-time and working condition adaptability of the energy allocation.In order to solve the problems,a coping strategy combining PMP and real-time working condition construction is proposed to achieve both global and transient optimal characteristics of energy management.Firstly,the minimization objective function of total hydrogen consumption for hybrid power system operation is derived based on the principle of minimal value,and the global optimal fuel cell reference power is solved offline.Secondly,the operating process is divided into five stages:idle traction,acceleration start,steady speed driving,deceleration braking and regenerative braking according to the real-time operating characteristics of the tram,and the corresponding state transfer probability matrices are constructed based on Markov chains to improve the adaptability of the energy management strategy to working conditions.At the same time,the fuel cell is classified into four modes:low efficiency,medium efficiency,high efficiency and super efficiency according to its power generation efficiency,and it is set not to start in the low efficiency mode,which can reduce the number of starts and stops of the fuel cell and improve its working efficiency,thus enhancing the engineering applicability of the proposed strategy.Finally,the results of the working condition construction are combined with the energy management,and the instantaneous optimal power allocation is updated online.The proposed strategy,traditional global PMP strategy and instantaneous equivalent consumption minimization strategy(ECMS)strategy are simulated under typical and atypical working conditions.The results show that:The hydrogen consumption of the proposed strategy is 3.76 kg under typical working conditions,which is reduced by 9.6%and 16.8%,respectively,compared with 4.13 kg under PMP strategy and 4.52 kg under ECMS strategy.Similarly,the hydrogen consumption of the proposed strategy is 5.25 kg under atypical working conditions.Compared with the consumption of 5.52 kg and 5.92 kg for PMP and ECMS,the consumption is reduced by 4.9%and 11.3%,respectively.The data indicating that the proposed strategy achieves the global optimal fuel economy.In terms of the calculation time of the optimization algorithm,the proposed strategy,PMP strategy and ECMS strategy are 37ms,2020 ms and 35 ms respectively under typical working conditions,and 32 ms,1820 ms and 29 ms respectively under atypical working conditions.Meanwhile,the proposed strategy can reduce the high power startup times and peak power fluctuation time of fuel cell,and further enhance the system rapidity on the basis of prolonging the service life of fuel cells.Combined with the simulation analysis, the core advantages of the proposed energy management strategy are: (1) overcoming the shortcomings of the global optimization strategy represented by the traditional minimum value principle in terms of real-time and working condition adaptability, and making the hybrid system power distribution both instantaneous and globally optimal. (2) Introducing the demand power prediction based on the identification of the operating state of the tram and dividing the fuel cell operating mode, which improves the working condition adaptability of the energy management strategy. (3) Compared with the traditional PMP strategy and ECMS strategy, the hydrogen consumption is reduced and the overall energy utilization efficiency of the system is improved under both typical and atypical working conditions, while the supercapacitor SOC and bus voltage fluctuation range are significantly improved.