Robust Stability of Networked Load Frequency Control Systems with Time-Varying Delays

In deregulated power system scenario coupled with smart grid technology, for networked load frequency control (LFC), an open communication structure, owing to low cost and flexibility, is preferred over dedicated networks in the feedback control loop for transmitting/receiving the data between the geographically displaced power system and the control center. In such a control scheme, closing the feedback loop through an open communication channel, in turn, introduces two additive time-varying delays of dissimilar characteristics in the feedback path. These delays degrade the performance of the closed-loop system, and exert a destabilizing effect on the overall system. In this paper, using Lyapunov-Krasovskii functional approach, a less conservative stability criterion is presented to ascertain delay-dependent stability of such network-controlled LFC systems with two additive time-varying delays in the feedback path in the presence of uncertain load disturbance conditions. Unlike the existing results, which are derived by combining these two delays into one, the proposed result considers the two delays as separate entities thereby imparting more generalization into the stability analysis. The effect of unknown exogenous load disturbance is incorporated by mathematically modeling them as a bounded non-linear time-varying function of current and delayed state vectors.     

Definition of the remaining life of power-transmission lines with cross-linked polyethylene insulation

XLPE-insulated cables and wires are becoming more widespread. For this reason, it is becoming necessary to control the state of insulation over its total operating life. Online monitoring of the effects on the insulation and determination of its remaining life becomes possible using modern equipment. In this paper, a method of determining the remaining lifetime of the cross-linked polyethylene insulation of the powertransmission line is presented. An insulation-aging model developed at the previous stage of the research was used. It is proposed to control the destructive effects on the insulation and calculate the remaining life based on the obtained data. The results of the research showed that the probability of failure is subject to the normal character of distribution (Gaussian distribution) as the insulation in the process of operation is exposed to a large number of effects (partial discharges, thermal actions, effect of the environmental factors, etc.). The remaining lifetime is defined as a function of inverse failure probability. The proposed method can be used to develop a set of devices for determining the remaining life of polyethylene insulation.     

Optimization of the parameters of the current transducer of block protection of electric motors

We determined the parameters of a current and voltage inductive transducer with a magnetic core made of a ferromagnetic material. The inductive transducer is used as a part of the block multifunctional protection of three-phase asynchronous electric motors. An equivalent circuit of a passive inductive current transducer is given. We determined the main relationships connecting the output voltage of the transducer with the measured current. Modeling of parameters was performed to expand the ranges of measured currents at a fixed frequency and in a wide frequency range. We examined the operating modes of the transducer at an idle speed, with a short circuit. The mathematical model takes into account the characteristics of the magnetic circuit, the possibility of its saturation, the higher harmonic components of the sensor output signal.     

A plasma device for increasing the hydrophilicity of paper products

The treatment of various materials using low-temperature gas–discharge plasma to clean their surface or change their structure is rather promising because of the generation of particles that react with molecules of impurities or base material. In addition, the molecules of the surface layer of material are exposed to the influence of ultraviolet and soft X-ray radiation generated in the cathode layer of the discharge. Only the volumetric gas–discharge can guarantee a high degree of uniformity of the material surface treatment. To increase the intensity of the plasma-chemical reactions, it is effective to increase the frequency of the supplied voltage of a discharge reactor or to use the pulse–periodic power-supply mode. The pulse frequency should be coordinated with the typical frequency of the plasma chemical reactions. Experimental installations that have a discharge reactor as their main element showed successful performance for the modification of the volumetric structure of a thin paper tape to increase its hydrophilicity.     

Low-profile patch antennas for biomedical and wireless applications

Printed microstrip-fed antennas based on a slotted radiating patch are proposed herein. First, a basic rectangular antenna without any slots was designed, being suitable for wideband applications and showing impedance bandwidth of 2714 MHz for \(S_{11} < -10\) dB. Next, dual-band operation for worldwide interoperability for microwave access (WiMAX, from 3.11 to 3.97 GHz) and wireless local-area network (WLAN, 4.97–5.71 GHz) was obtained by including slots only on the left side of the basic design. Then, using a structure with slots on the right side of the radiating patch, WLAN operation was obtained in the frequency range of 2.865–2.096 GHz. The fourth antenna, with slots on both sides of the patch, was characterized and realized for biomedical applications at 2.45 GHz (\(S_{11} <-10\) dB). The proposed antennas can be realized with small ground plane size and total antenna area of only \(27.5 \times 21\,\hbox {mm}^{2}\). This reduction in total antenna area is achieved by using a truncated patch. All the simulations were carried out using Empire XCcel. The designs were characterized based on their radiation pattern, return loss, voltage standing wave ratio (VSWR), gain, and current distribution. The simulated and measured results show good compatibility.     

塞浦路斯考古博物馆

正建筑师Theoni Xanthi获得新塞浦路斯国际建筑竞赛一等奖。此次竞赛分为两个阶段,第一阶段共收到129份参赛作品,第二阶段入围7份作品。项目耗资7 500万欧元,新的考古博物馆将容纳塞浦路斯考古机构所有的重要收藏;同时,博物馆作为"文化之岛"——尼科西亚市的多功能文化设施,功能包括文物部办公室、会议室、图书馆、咖啡馆及餐厅、文化活动平台及一个达42 000平方米的开放的底层景观平台。考古博物馆坐落在离尼科西亚中世纪城墙不远的地方,处于城市绿地与城市中心区的中间地带。因此,作为应对,     

Peat swamps at Giral lignite field of Barmer basin,Rajasthan, Western India: understanding the evolution through petrological modelling

International Journal of Coal Science & Technology - The lignite samples collected from Giral lignite field of Barmer basin have been subjected to petrological investigation. The data generated...     

Distribution of mineral species in different coal seams of Talcher coalfield and its transformation behavior at varying temperatures

International Journal of Coal Science & Technology - Mineral phase characterization and thorough understanding of its transformation behavior during combustion are imperative to know the...     

Peculiarities of chemical elements accumulation by epiphytic moss Pylaisia polyantha (Hedw.) B.S.G. in varying natural environments of West Siberia

This study explores the influence of natural environment on the content of chemical elements in the epiphytic moss Pylaisia polyantha, picked from six areas remote from industrial centres in Siberia. The neutron activation analysis determined concentrations of 25 chemical elements (mostly heavy metals). According to correlation analysis, none of the climatic variables (i.e. temperature, precipitation and airflow direction) is separately significant for the accumulation of the examined chemical elements by the moss. The concentrations of chemical elements in mosses picked in different plant subzones or belts definitely vary. This means that the environment characteristic of plant subzones or belts and phytocenosis types influence the accumulation of chemical elements in the moss. The sample selection area belongs to a certain plant subzone or belt and this reflects the overall influence of climatic and other ecological factors. However, phytocenosis properties (i.e. stand thickness, canopy density degree, etc.) impact the concentration of chemical elements in the epiphytic moss primarily due to the sunshade effect.     

Stripping with direct dumping in Kuzbass open pit mines: The current state and prospects

The analytical results are given for application of stripping with direct dumping in open pit mines in Kuzbass. It is emphasized that this most productive and the least power-consuming technology loses its weight in the overall content of overburden stripping. The authors propose a method to determine rational boundaries for application area of stripping with direct dumping using slice re-excavation coefficient. The scope of the discussion comprises potential trends of the technology and use of draglines towards enhancement of open pit mining efficiency.