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In this paper, the complex relationship between environmental variables and dam static response is expressed using composition of functions, including nonlinear mapping and linear mapping. The environmental effect and noise disturbance is successfully separated from the monitoring data by analysis of the covariance matrix of multivariate monitoring data of dam response. Based on this separation process, two multivariate dam safety monitoring models are proposed. In model I, the upper control limits (UCLs) are calculated by performing kernel density estimation (KDE) on the square prediction error (SPE) of the offline data. For new monitoring data, we can judge whether they are abnormal by comparing the newly calculated SPE with the UCL. When abnormal data are detected, the SPE contribution plots and the SPE control chart of the new monitoring data are jointly used to qualitatively identify the reason for the abnormalities. Model II is a dam monitoring model based on latent variables that can be calculated from the separation process of the environmental and noise effects. The least squares support vector machines (LS-SVMs) model is adopted to simulate the nonlinear mapping from environmental variables to latent variables. The latent variables are predicted, and the prediction interval is calculated to provide a control range for the future monitoring data. The two monitoring models are applied to analyze the monitoring data of the horizontal displacement and hydraulic uplift pressure of a roller-compacted concrete (RCC) gravity dam. The analysis results demonstrate the good performance of the two models. 相似文献
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根据上海轨道交通的实际情况,简要介绍了轨道交通直流牵引系统的原理和构成,直流牵引系统继电保护的构成,双边联跳构成、原理以及双边联跳的实际构成方式,并对双边联跳的调试提出了一些方案和建议。 相似文献
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闪变包络线检测是分析电压波动与闪变的关键。IEC推荐的平方检测法在闪变低频段的包络线提取误差较大,不适合风力发电并网产生的电压闪变包络线提取。文中针对风电并网引起的电压闪变问题,提出了基于稀疏复原算法的闪变包络线提取方法。以电压闪变信号的极值点作为观测序列,根据闪变包络线低频段较平稳的变化特性,构造变频宽的离散余弦变换基,利用正交匹配追踪算法还原出最佳闪变包络线。通过对单一频率闪变、复合频率闪变、基波频率变动、谐波及噪声影响的电压闪变信号进行分析,表明了该算法提取闪变包络线的准确性。最后,通过对张北柔直电网中新能源风电场实测的电压波动信号进行分析,进一步验证了所提算法提取风电并网引起的电压闪变包络线的可行性与有效性。 相似文献
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《International Journal of Electrical Power & Energy Systems》2012,42(1):137-144
Special Protection Systems (SPSs) are one of efficient tools to limit the consequences of instability in case of happening large disturbances in power systems. Generator Rejection Systems (GRSs) are the mostly used forms of SPS. Offline GRS suffers from drawback of inaccuracy and increased risk when power system operating point differs from the nominal value. By predicting the future trend of bus phase angles, online GRS offers a lower risk than the offline scheme, especially when its parameters are appropriately tuned. In this paper, the effect of online GRS parameters including the starting time and width of the data window used for prediction on its performance is thoroughly investigated. The risk analysis of online GRS is evaluated under different conditions and compared with that of offline and no GRS schemes. To enhance the efficiency and accuracy of online GRS, an optimal data window is proposed. As an intriguing result, using a wider data window does not always result in a better accuracy of online GRS and the starting point of the data window has a vital effect on the performance of online GRS. The GRS schemes are tested on the WSCC test system and results are discussed in detail. 相似文献
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结合近几年来南方电网多次出现的变压器空投涌流引起直流50 Hz保护动作事件,仿真研究了励磁涌流、和应涌流及故障电流波形特征差异性,在不降低保护灵敏度的原则下,提出了一种基于波形识别的直流50Hz保护优化改进策略,并在高压直流PSCAD/EMTDC控制保护仿真模型的基础上结合优化改进策略自定义创建直流50Hz保护闭锁模型,从交流系统强度变化、换流变压器空载合闸角变化、换流变压器铁芯剩磁变化三个角度对所提出的优化策略进行仿真验证。结果表明,所提出的基于波形识别的直流50Hz保护优化改进策略能正确地实现直流50 Hz保护的闭锁和解锁,在不影响直流系统安全稳定运行的情况下很好地解决了变压器空投涌流引起直流50Hz保护误动的问题。 相似文献
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《Journal of power sources》2005,144(2):418-425
Various attempts have been made to use impedance measurements for online analysis and offline modelling of lead–acid batteries. This presentation gives an overview on the latest and successful approaches based on impedance measurements to assess state-of-charge (SoC), state-of-health (SoH) and cranking capability of lead–acid batteries. Furthermore, it is shown that impedance data can serve as a basis for dynamic battery models for the simulation of vehicle power-supply systems. The methods and procedures aim for a reliable prediction of battery performance in electric vehicles, hybrid cars and classical automotive applications. Although, it will become obvious that impedance measurements give valuable information on the battery state, typically the information needs to be combined with other conventional algorithms or self-learning tools to achieve reliable and stable results for real-world applications. 相似文献