Development of a double-layer shaking table for large-displacement high-frequency excitation

It is difficult to conduct shaking table tests that require large-displacement high-frequency seismic excitation due to the limited capacity of existing electrohydraulic servo systems.To address this problem,a double-layer shaking table(DLST)is proposed.The DLST has two layers of one table each(i.e.,an upper table and lower table)and aims at reproducing target seismic excitation on the upper table.The original signal is separated into two signals(i.e.,a high-frequency signal and low-frequency signal)through a fast Fourier transform/inverse fast Fourier transform process,and these signals are applied to the two tables separately.The actuators connected to different tables only need to generate large-displacement low-frequency or small-displacement high-frequency movements.The three-variable control method is used to generate large-displacement but low-frequency motion of the lower table and high-frequency but small-displacement motion of the upper table relative to the table beneath.A series of simulations are carried out using MATLAB/Simulink.The simulation results suggest that the DLST can successfully generate large-displacement high-frequency excitation.The control strategy in which the lower table tracks the low-frequency signal and the upper table tracks the original signal is recommended.

Measurement of algae PSII photosynthetic parameters using high-frequency excitation flashes

We establish a system to measure the functional absorption cross section of photosystem lI （PSII） （O-PSII） and maximum quantum yield of photochemistry in PSII （Fv/Fm）. The system utilizes a sequence of high-frequency excitation flashes at microsecond intervals to induce a microsecond-level fluorescence yield curve. Parameters o-Psii and Fv/Fm are calculated by fitting the curve using nonlinear regression. Experimental results show that the relative standard deviation （RSD） of the system is less than 3%, and the correlation coefficient of Fv/Fm values measured by this system and those measured by pulse amplitude modulation method is 0.950.

电脉冲除冰系统除冰激励的仿真研究

建立了电脉冲除冰实验系统的二维电磁涡流场分析模型,提出了数值计算后处理求解试验蒙皮表面除冰激励分布的方法,并利用有限元动力分析方法建立了试验蒙皮的三维动力分析模型,通过在模型上加载后处理所得的表面瞬态压力,仿真获得了试验蒙皮的响应加速度,最后引入加速度实验用以验证模拟值。结果表明,基于二维电磁涡流场数值计算后处理求解除冰激励与有限元动力分析试验蒙皮的方法,所得的加速度与实验测量值吻合较好,因此说明了所述方法的正确性,可为电脉冲除冰系统的冰层破坏分析奠定基础。

输电线路高频、高压激励融冰技术研究

针对2008年南方电网50年未遇的罕见冰雪灾害情况,介绍了国内外输电线路高频、高压融冰有关理论及当前研究状况。参照110kV输电线路建立融冰仿真计算模型,对不同线路长度、频率、冰介质参数进行仿真计算,对融冰设备的设计、制造进行了初步分析,提出了需要进一步研究的问题和研究思路。

对流换热对覆冰导线高频融冰温度分布的影响

根据流体力学的基本原理,应用有限元分析软件ANSYS建立覆冰导线高频融冰时的外流场模型,得到覆冰导线高频融冰时的周围空气流场、压力场分布规律及覆冰导线表面对流换热差异性。分析了高频融冰过程中的热量损失和对流换热的影响因素,通过电磁与热分析,揭示了高频激励融冰过程呈不均匀非对称融冰规律,覆冰导线迎风侧压力大、温度低,背风侧压力小、温度高,表明不均匀对流换热使覆冰导线背风侧先融化,迎风侧后融化。在环境温度和覆冰厚度一定的条件下,覆冰导线外表面温度随对流换热系数的增大而降低。

基于高频激励法的输电线路融冰激励源研究

针对当前输电线路融冰技术的缺陷,国外有学者提出了一种在线高频激励融冰方法。此方法具有可实现在线融冰、融冰电流小和融冰效率高等优点,但成套融冰设备未得到深入研究。为推进此融冰方法在输电线路中的实际应用,提出一种针对500 kV交流输电线路的移动式高频融冰激励源设计方案,重点分析并计算了移相变压器与功率单元相关参数,并运用MATLAB对级联式高频激励源进行仿真。结果表明,此方案可行且具有谐波含量低、输出电压稳定等优势。