基于自适应多分辨率分析的电动拖拉机驱动功率分配策略

    Drive power allocation strategy for electric tractor based on adaptive multi-resolution analysis

    • 摘要: 燃料电池分布式驱动电动拖拉机(fuel cell distributed drive electric tractor,FCDET)能够有效解决环境污染和能源紧缺问题、推动农业可持续发展。针对FCDET牵引效率低、续航时间短、氢耗量大等问题,该研究提出了基于自适应多分辨率分析(adaptive multi-resolution analysis,AMRA)的犁耕驱动功率分配策略。首先建立燃料电池系统等效电路模型、总效率求解模型、能量耗散模型以及驱动电机响应模型。一次重构策略基于可调Q因子小波变换(tunable Q-factor wavelet transform,TQWT),获得有效反应功率信号振荡特性的子序列。二次重构策略将低频子序列经过变分模态分解(variational mode decomposition,VMD)为若干个具有特殊稀疏性质的离散子信号。然后采用麻雀搜索算法(sparrow search algorithm,SSA)实时获取VMD的分解层数和二次惩罚因子的最优组合。最后将二次分解后的子序列和子信号按照频率特性进行重构,并将重构功率信号在各个能量源之间重新分配。以ET504-H样机为对象,通过田间试验采集犁耕载荷功率需求信息,并进行驱动电机台架试验。结果表明:基于AMRA的FCDET驱动功率分配策略能够有效提高燃料电池系统的能量利用率和犁耕作业的经济性。相较于功率跟随策略和一次重构策略,燃料电池系统的平均效率分别提升了8.30%和1.82%,等效氢耗量分别降低了35.60%和11.86%;驱动电机平均效率分别提升2.06%和1.27%,总能耗分别降低3.73%和2.60%。研究结果可为FCDET控制系统研发提供新的理论基础和技术途径。

       

      Abstract: Agricultural machinery and equipment are indispensable to realize resource utilization for high efficiency in sustainable production. It is also required for the efficient, intelligent, and environmentally friendly agricultural power machinery, due to the greenhouse gas emissions and the drastic reduction in the extraction of non-renewable resources. Fuel cell distributed drive electric tractors (FCDET) can provide a new approach to developing green agricultural machinery. However, the great challenge has posed on the traction efficiency, short range, and high hydrogen consumption. A reasonable and effective power allocation can be expected to reduce energy consumption for the high efficiency of the fuel cell system. In this study, an allocation strategy of plowing drive power was proposed for FCDET using adaptive multi-resolution analysis (AMRA). The effective decoupling between the various energy sources was also realized to reduce the frequent start-stop and the large power fluctuations of the hydrogen fuel cell. Firstly, two models were established for the fuel cell system and the total efficiency solver. The first-time reconstruction was to obtain the subsequence that effectively responded to the oscillation characteristics of the power signal using the tunable Q-factor wavelet transform (TQWT). The second reconstruction was to decompose the low-frequency subseries into several discrete sub-signals with special sparse properties using variational mode decomposition (VMD). Then, the sparrow search algorithm (SSA) was used to obtain the optimal combination of modal decomposition layers and quadratic penalty factors for VMD in real time. Finally, the second-time decomposed subsequence and sub-signals were reconstructed, according to the frequency characteristics. The reconstructed power signal was redistributed among the various energy sources. A test was carried out to verify the power allocation. The power demand information of the drive motor was acquired for FCDET plowing conditions at the China YTO Mengjin test base, taking the ET504-H prototype as the object. The plowing condition included a 0-8.7 s starting stage and an 8.7-18.0 s stable plowing stage. The demand power signal shared a large rate of change in the starting stage and a large high-frequency characteristic in the stable plowing stage. In addition, another experiment was carried out on the transmission bench in the New Energy Key Laboratory of Henan Province, in order to test the cooperative operation of permanent magnet synchronous motors (PMSM) under three power allocations. The results showed that the FCDET drive power allocation using AMRA effectively improved the energy utilization of the fuel cell system and the economy of the whole vehicle in plowing condition. The fuel cell system efficiency was improved by 8.30% and 1.82%, respectively, compared with the power-following and the first-time reconstruction. The equivalent hydrogen consumption was reduced by 35.60% and 11.86%, respectively. Meanwhile, the drive motor efficiency was improved by 2.06% and 1.27% on average; the energy consumption was reduced by 3.73% and 2.60%, respectively. This finding can provide a novel theoretical and technical approach for the development of the FCDET control system.

       

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