A fuel-cell/battery hybrid DC backup power system via a new high step-up three port converter

In this paper, a fuel-cell (FC)/battery hybrid direct-current (DC) backup power system is proposed for high step-up applications. This system is composed of a newly developed non-isolated three-port converter, which achieves a high voltage gain by taking the advantage of a quasi Z-source network and an energy transfer capacitor. After analyzing the converter, a comprehensive comparison study and a design procedure are provided. Moreover, the controllers regulating the source power levels while smoothing the FC power profile according to the proposed energy management strategy (EMS) are designed based on the developed small-signal model of the proposed converter. Both hardware and controller design procedures are validated through the PSIM model of the whole system. As a result, it is shown that the proposed system can effectively couple FC and battery while transferring their energies to a high voltage DC bus according to the offered EMS.     

An unsupervised approach for fault diagnosis of power transformers

Electrical utilities apply condition monitoring on power transformers (PTs) to prevent unplanned outages and detect incipient faults. This monitoring is often done using dissolved gas analysis (DGA) coupled with engineering methods to interpret the data, however the obtained results lack accuracy and reproducibility. In order to improve accuracy, various advanced analytical methods have been proposed in the literature. Nonetheless, these methods are often hard to interpret by the decision-maker and require a substantial amount of failure records to be trained. In the context of the PTs, failure data quality is recurrently questionable, and failure records are scarce when compared to nonfailure records. This work tackles these challenges by proposing a novel unsupervised methodology for diagnosing PT condition. Differently from the supervised approaches in the literature, our method does not require the labeling of DGA records and incorporates a visual representation of the results in a 2D scatter plot to assist in interpretation. A modified clustering technique is used to classify the condition of different PTs using historical DGA data. Finally, well-known engineering methods are applied to interpret each of the obtained clusters. The approach was validated using data from two different real-world data sets provided by a generation company and a distribution system operator. The results highlight the advantages of the proposed approach and outperformed engineering methods (from IEC and IEEE standards) and companies legacy method. The approach was also validated on the public IEC TC10 database, showing the capability to achieve comparable accuracy with supervised learning methods from the literature. As a result of the methodology performance, both companies are currently using it in their daily DGA diagnosis.     

汽轮机运行调节方式优化策略探析

分析了汽轮机的喷嘴调节、节流调节、旁通调节、定压调节和滑压调节等几种基本调节方式的特点,指出现役燃煤火电机组多因调节方式单一而普遍存在着调峰能力不足、负荷响应迟缓以及因长期偏离设计工况致使运行安全经济性下降等诸多问题,提出了通过调节方式的优化组合,采用(节流)定压-滑压-(喷嘴)定压-旁通调节的复合调节方式,以实现煤电机组安全、经济、灵活、快速地参与电网的深度调峰,破解具有强随机波动性的新能源电量规模化并网的困境。     

Lightweight reactor design by additive manufacturing for preheating applications using metal hydrides

Thermal energy storage systems based on metal hydrides can be a solution for preheating fuel cells (FCs). They can provide thermal energy at temperatures below −20 °C during startup, while heat at 50 °C during operation is sufficient for regeneration. The challenge of such a system in mobile applications is the final weight specific thermal power. In this study, a reactor design based on additive manufacturing techniques for ~300 g of metal hydride is presented. Here, a reactor (passive) to hydride (active) mass ratio of 0.97 is realized, still reaching high weight specific thermal power of up to 2.1 kW/kg_MH at −20 °C and 8 bar (LmNi_4.91Sn_0.15). Considering the example of preheating a FC from −20 °C in ~120 s, the performance of LaNi₅ and LmNi_4.91Sn_0.15 is studied. While LaNi₅ requires higher regeneration temperatures than LmNi_4.91Sn_0.15 (>40 °C compared to >20 °C), its performance is less sensitive to operative variations due to its nearly ideal thermodynamic characteristic.     

Information system business affecting impact evaluation method

To effectively analyze the impact of continuous business interruption on the information system,an information system business affecting impact evaluation method (IBAIE) is proposed.First,we identify the main businesses of the system and quantify their vulnerability.Then,we take the businesses as the nodes of network topology and weight nodes based on the business significance.The orderly association between businesses is taken as the edges which are weighted based on the association between asset and business,and the directed weighted business network topology is obtained.Finally,the method of directed weighted network structure entropy is used to evaluate the change of system business network structure during the period from business interruption to recovery.Experiments show that this method has obvious advantages in evaluating accuracy compared to other methods,and can be applied in ensuring information system security.     

Using deep learning to combine static and dynamic power analyses of cryptographic circuits

Side-channel attacks have shown to be efficient tools in breaking cryptographic hardware. Many conventional algorithms have been proposed to perform side-channel attacks exploiting the dynamic power leakage. In recent years, with the development of processing technology, static power has emerged as a new potential source for side-channel leakage. Both types of power leakage have their advantages and disadvantages. In this work, we propose to use the deep neural network technique to combine the benefits of both static and dynamic power. This approach replaces the classifier in template attacks with our proposed long short-term memory network schemes. Hence, instead of deriving a specific probability density model for one particular type of power leakage, we gain the ability of combining different leakage sources using a structural algorithm. In this paper, we propose three schemes to combine the static and dynamic power leakage. The performance of these schemes is compared using simulated test circuits designed with a 45-nm library.     

1 GWt PB-FHR负荷跟踪运行特性分析

为研究熔盐堆系统在商业应用中的价值，分析其是否满足电网负荷的变化需求和安全运行的能力，本文以1 GWt球床式氟盐冷却高温堆（PB-FHR）为研究对象，仿真计算其在负荷跟踪模式下的瞬态行为和运行特性。以RELAP5/MOD4.0程序为研究工具，并植入相关的熔盐物性与计算关系式，建立氟盐冷却高温堆的热工水力系统与功率控制系统的仿真模型，对典型负荷工况参数变化情况下控制系统的响应特性进行仿真分析。结果表明：该氟盐冷却高温堆系统在设计的控制逻辑的调控下，展示出良好的负荷跟踪运行能力，堆芯功率能迅速响应负荷变化，功率超调和温度超调小，反应堆的运行参数始终处于合理的运行范围内。     

核电厂负刚度阻尼隔震结构的地震响应研究

隔震技术能有效减小核电厂上部结构的加速度响应，但强地震作用下隔震层位移过大会导致管道断裂。本文基于曲面运动原理及预压弹簧伸缩特性提出了一种负刚度阻尼系统，通过球铰在拱球面曲线运动实现负刚度特性，并在弹簧压缩方向提供黏滞阻尼性能。提出了负刚度系统的理论恢复力模型并进行了力学特性分析，设计了负刚度装置并完成了静力试验，结果显示理论恢复力模型与试验结果的一致性较理想。将核电厂负刚度阻尼隔震结构与核电厂隔震结构进行了地震响应对比分析，比较了不同地震波输入下的地震响应。结果表明负刚度阻尼系统可有效同时减小核电厂上部加速度响应和隔震层位移响应。     

核电厂应急监测计划的关键问题及探讨

应急监测计划是核电厂应急计划的重要支持性文件,是核电厂应急监测准备和响应的重要依据。本文从核电厂事故应急监测方案、监测方法、监测设施设备配置、应急监测响应、监测能力的保持、质量保证等关键问题进行分析研究,提出相关建议,为核电厂应急监测计划的制订提供参考。