Applied Mechanics and Materials Vols. 713-715

Abstract: Based on the classical Mayer-arc model, this paper establishes the equivalent circuit of traction network for AC25kV electric railway from the essence of contact loss discharge. The voltage waves of contact loss arc at different moments are obtained by MATLAB/simulink. Through the analysis, it can be confirmed that the EMI (electromagnetic interference) with broad band and high amplitude will appear at the moment the contact loss between pantograph and catenary happens. Finally, relevant measures are given to avoid the probability event of contact loss.

Abstract: The working principle of Programmable Logic Controller (PLC) is introduced. Three kinds of PLC programming method, logic based method, function based method and Petri Net based method are emphasized. The example is also given. It also points out that function based PLC programming method is a practical engineering method.

Abstract: With the implementation of State Grid’s management system, ‘Three Intensive Management And Five Large-scale Movements,’ it is inevitable for municipal power supply enterprises to promote and build value management. Based on value management, with management features of municipal power supply enterprises’ other expenses, whole process management will be combined with enterprises’ realities to build management system for other expenses, strengthen control of other management expenses in the event, track key projects and form a closed-loop dynamic cost management, which will make up for lack of the feedback of traditional cost management mode on other management expenses.

Abstract: In this paper a capacitor step-down regulated power supply based on current conduction angle adjustable mode is proposed. The circuit of capacitor step-down regulated power supply has simple structure, low cost, output short circuit and less loss, it is widely used in driving power supply with small power. But the conventional capacitor step-down power supply has no voltage stabilizing, it cannot work between wide voltage ranges from 180V to 260V. This power can drive LED lamp group which power range is from 5W to 20W. It has less EMI, stable work, low cost and simple maintenance.

Abstract: To solve the problem of vehicle adhoc network reliability is not high and multi-channel hidden terminals, we propose a multi-channel MAC protocol CAMP(cooperation-based asynchronous multi-channel MAC protocol) based mechanism for asynchronous cooperation in VANET. CAMP add to cooperation mechanisms in asynchronous multi-channel environment, the proposed scheme nodes cooperation in order to obtain the channel state information and status information to other nodes, thus a good solution to the hidden terminal problem multichannel transmission process, to achieve high mobility environment under the reliable transmission of data. The simulation results show that CAMP has better performance than IEEE 1609.4 standard, AMCP protocol, AMCMAC protocol on collision probability of SCH, safety messages delivery ratio.

Abstract: Problems such as low voltage and big line loss have long existing in the power grid in rural areas of China. In recent years, some province and cities have improved voltage and reduced line loss by installing SVG at substations in rural power grids, and the effect is remarkable.With great compensation capacity and a good variety of modes of compensation, SVG is sure to replace old reactive compensation devices in rural power grid in future, which requires evaluation and analysis of SVG reliability so as to guarantee safety and stability of the power grid. However, now no research or analysis has been made in China on SVG reliability in rural power grids, which affects wide promotion of SVG in rural power grids.Under the background of Liaoning Power Grid 10kV/±5Mvar Chain SVG, this paper analyzes the reliability of k/n (G) system model of SVG master circuit structure, improving the accuracy of system reliability estimation. The estimation matches the operation outcome, thus providing data basis for the feasibility of SVG’s wide application in rural power grid in future.

Abstract: As SVG products get more and more popular, new products keep being developed for the demand of actual operation. Intensive SVG is a new kind of SVG developed on the basis of conventional SVG products. The main characteristic of the so-called “intensive SVG” is the draw-out type power module which is featured by small volume, low loss and strong environmental adaptability. The power unit is the core of SVG and its reliability is the foundation on which the entire system functions. Therefore, the reliability evaluation is of vital importance. In this paper, a method of studying its reliability by setting up a reliability module is introduced, which may help with equipment maintenance in future.

Abstract: In a rural power grid 220kV transformer substation in Liaoning Province, because of the appearance of a lot of new impact loads in the power supply area, the original reactive power repertory can not meet the existing load need. As a result, the output 66kV voltage fluctuation affects the power supply security of the users. After a comprehensive evaluation, it is planned to set up a set of ±100M SVG to increase the reactive power repertory to stabilize the system voltage. The electrical system of 220kV transformer substation is huge and often meets with sudden failure; and the capacity of this set of SVG is large, so it may worsen the situation in case of improper control. This paper discusses several operational modes that SVG should have and designs a scheme that can be flexibly switched in several operational modes, which is specifically executed by an overall coordination module. This method has passed the preliminary field operation verification.

Abstract: The algorithm of rapid ambiguity resolution for single frequency receivers is presented in this paper. Firstly, a sequential least square method is applied to decrease dimensions of the observation matrix of satellites. And then, the regularization method is applied to improve the accuracy of the float solution of ambiguities. Finally, the evolutionary method is applied to search the fixing solution of ambiguities. The experiment results show that the proposed method is fast and efficient for users to perform kinematical positioning and the difference between the positioning results of the proposed method and the results of GrafNav is in 2.5 cm.

Abstract: To further improve the performance of channel estimation by particle filtering, an improved particle filtering method was proposed. The HF channel has multipath、fading and time-varying characteristics, and using the dynamic channel prediction model and the phased semi-blind estimation by improved particle filtering can obtain the tracking performance for the time varying channel. Based on stratified resampling of particle filtering, a criterion is set during the particle choosing process to ensure the valid of the chosen particles. Simulation result shows the effectiveness of the proposed method.