In this paper, the stability problem of load frequency control (LFC) based power systems with two additive interval time-varying delays is studied. Firstly, considering the time delays of transmission from control center to regulator and sensor to control center, the mathematical model of two-area LFC power system based on proportional integral control is established. Secondly, under the condition that the lower bounds of interval time-varying delays are non-zero, an augmented Lyaounov-Krasovskii functional (LKF) is constructed, and a new delay-dependent stability criterion is derived. Since the extension of LKF introduces the nonlinear term of time-varying delay square, a new negative definite integral inequality transformation lemma is used to transform the nonlinear matrix inequality in the stability criterion into linear matrix inequality (LMI) equally-without introducing additional conservatism. Finally, the maximum stability margin of the LFC power systems is obtained by using MATLAB LMI-toolbox, and simulation results based on Simulink-toolbox show the effectiveness of the stability criterion.

换流站运行中伴随噪声污染,影响范围广,噪声成分复杂,噪声抑制难度较高.鉴于此,论文结合工程实例,阐述了换流站对环境的影响,基于维护环境的前提,从控制噪声、电磁辐射及无线电干扰等多个角度,对设计换流站过程中应具备的技术保护举措与建议进行细致探讨.

针对广州南沙区拟建的110 kV保税输变电站站址的深厚淤泥层软土地基处理问题,采用石灰桩复合地基处理方式进行加固.为克服传统石灰桩机械化程度低的缺点,利用开发的扩径石灰桩成套装备与工艺施做了3种不同间距条件下共28根试验桩,通过试验前后钻孔取芯、静力触探以及无侧限抗压强度试验等,对不同桩间距条件的石灰桩复合地基桩间土承载力以及复合地基承载力进行了评估.基于Biot固结理论的有限元方法,对不同间距条件下的石灰桩复合地基沉降规律进行了探讨.验证了扩径石灰桩工艺可行性的同时,也为石灰桩软基处理的设计施工提供依据.

For extra-high voltage transmission lines configured with a communication channel, the current differential protection is facing a dilemma between sensitivity and security. On the one hand, the resistive coverage will not be sufficiently high if security is guaranteed. Although the sequence-current-based differential elements are more sensitive, it may cause a longer time delay and deteriorate sensitivity under the open-phase operating condition. On the other hand, if high sensitivity is guaranteed at the cost of security, the main protection element will be blocked in the current transformer (CT) saturation scenario. To solve this problem, a novel type of impedance differential protection (IDP) is proposed. Under the open-phase condition awaiting an automatic reclosing, the proposed IDP can assist in accelerating the speed of fault-clearance for healthy phases, which is faster and more sensitive than using the zero-sequence current differential protection. For an external fault with heavy CT saturation, the proposed IDP can take over the fault identification capability before the recovery of CT, in which duration the current differential protection is blocked. Simulation results indicate that the proposed IDP coordinate perfectly with the current differential protection in the above two scenarios. The performance of the proposed IDP is also assessed using field data.

本研究通过坍落扩展度试验、J环试验、V型漏斗试验和筛析稳定性试验对聚丙烯纤维增强混凝土拌合物进行新拌性能试验研究,探讨水灰比、纤维掺量和纤维长度对混凝土拌合物流变性能的影响.研究结果表明,除了水灰比,聚丙烯纤维掺量和长度也对混凝土拌合物的和易性、间隙通过性、流动性和抗离析稳定性有重要影响.

近年来,我国电力事业发展速度的日益加快,变电站作为其重要的一部分,自身的运行的安全性以及稳定性与电网的可靠运行有着很大关联.因此,为了能够进一步的对变电站运行安全性进行提高,在具体的发展过程中,应该强化对现代化先进技术的应用.基于此,本文即对变电站的BIM技术应用现状进行了分析,希望可以为相关人员提供一定的帮助.