计及常用恒流工况的锂离子电池建模方法

锂离子电池(LiB)的开路电压U_(oc)和内阻R是对LiB进行特性评估的重要参数。由于两者与LiB的荷电状态(SOC)、电流I及温度T呈非线性耦合关系,难以为工程应用建立一个参数(U_(oc),R)相对于这些变量的准确的解析模型。该文提出一种工程性建模方法,旨在建立参数(U_(oc),R)与LiB常用恒流工况范围内的变量(SOC,I,T)之间的映射关系。该方法首先在LiB常用工况范围内设计多个恒流工况实验以获取包含变量(SOC,I,T)典型信息的实验数据;其次采用一套数据处理方法解决LiB运行中SOC与T同时变化问题,并测算典型工作点{SOC,I,T}下的(U_(oc),R);最后分析SOC、I、T到U_(oc)及R的映射关系,并构建开路电压模型U_(oc)(SOC,T)和内阻模型R(SOC,I,T)。与现有方法相比,该方法建立的模型涉及的工况全面、实验时间短、参数估计精度高,适用于LiB工程应用和特性研究。实验结果验证了该方法的有效性。

双有源桥变换器最小电流应力和ZVS软开关优化实现研究

为减少双有源桥变换器功率损耗,提出一种综合考虑电流应力和ZVS软开关的优化控制方案。相较其他优化控制方案,该方案无须实时检测传输功率,更易于实现实时闭环控制。根据对传输功率、电流有效值和ZVS软开关分析,将电流有效值优化问题转换为以电流有效值为目标函数、以传输功率和软开关为限制条件的条件极值问题。通过分析EPS+SPS控制方案下的传输功率特性和软开关范围,建立漏感电流有效值、传输功率及软开关条件的数学模型;运用改进的拉格朗日极值法得出优化控制轨迹,保证全功率范围内ZVS软开关及电流应力最小;最后,仿真及实验结果验证了理论分析的正确性。

In-situ Synthesis and Characterization of Poly(vinyl alcohol)/Hydroxyapatite Composite Hydrogel by Freezing-thawing Method

Poly(vinyl alcohol)/hydroxyapatite(PVA/HA) composite hydrogel was successfully in-situ synthesized via three cycles of freezing-thawing. The composition and structure of products were investigated by X-ray diffraction( XRD), Fourier transformed infrared spectroscopy(FTIR) and scanning electron microscopy(SEM). The influence of different preparation methods and contents of material on the mechanical properties of PVA/HA composite hydrogel was discussed through tensile and compressive tests. The template of PVA could avoid the agglomeration of HA particles, which improves the mechanical properties of the composite hydrogel effectively. The tensile strength, modulus and compressive performances of the PVA/HA composite hydrogel prepared by the in-situ synthesis method were better than those of hydrogel obtained by the simple blend metliod. In addition, the effect of the content of PVA, HA, and the pH value on tlie properties of tlie PVA/HA composite hydrogel has been discussed in detail.