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In the background of Voltage Source Converter HVDC (VSC-HVDC) gradually coming into practice, fault ride-through control for wind farm connected to a VSC-HVDC system can maintain system stability, but also impact on the wind generators. To study on fault ride-through problem for wind generators in a VSC-HVDC system, this paper establishes a simulation model of two-terminal VSC-HVDC system including...
Ice-clad transmission lines can seriously damage a power grid, causing a partial or entire breakdown. De-icing the transmission line is a good method to prevent recurrence of such a situation. The development of dc de-icing technology can make difference in power grids preventing an ice disaster. Based on the calculation, analysis, and tests in the artificial climate chamber of the conductor de-icing...
Hydraulic control system is a typical highly nonlinear system, the loops of the system are coupled each other, so that the failure modes, failure mechanism of the hydraulic control system is very complex and diverse. Fault diagnosis of hydraulic control system is a uncertainty, incomplete information systems, which makes wrong diagnosis. Directing to the hydraulic press's hydraulic control system,...
SQL injection is an attack technique used to exploit code by altering back-end SQL statements through manipulating input. This paper proposes a novel methodology of preventing SQL injection attacks by building a protective adaptive shell. The protective shell is located between the application and the back-end database and has three layers to block illegal SQL statements. It could be adaptive after...
The paper combined the advantage of particle swarm optimization algorithm (PSO), the global optimizing ability of Hopfield Neural Network, and the teacher supervising features of BP neural network to construct a new equipment fault diagnosis method with higher diagnosis precision, compared with the traditional single BP neural network.
Modern industrial equipments need to be monitored on-line to ensure the machines work in normal state. In order to track the state of the machines in remote place, the monitoring signal analysis for the machines was realized in remote equipment on-line monitoring system based on B/S structure, which was developed by ASP.NET. In the system, the real monitoring vibration signal is transmitted to the...
In order to evaluate the bilingual instructing process and help the university acquire timely feedback information from students, a Bilingual Teaching Evaluation System based on BP neural network is established. Based on the investigation and analysis of the bilingual instructing process in Nanchang University, an evaluation index system is built, which consists of 14 indices. Take the 14 evaluation...
Directing to the inconsistency of the fault diagnosis information, a method of the rules extraction for fault diagnosis based on rough set theory and decision network is proposed. The fault diagnosis decision system attributes are reduced through discernibility matrix and discernibility function firstly, and then a decision network with different reduced levels is constructed. Initialize the network's...
BP neural network is easily trapped into the local minimum during the training process, which results that it can't get the optimal solution, even misjudging in device fault diagnosis. Directing to the above problems, a Hopfield-BP neural network fault diagnosis method was proposed, which combined Hopfield neural network, having the global optimal neural network computing ability, with the BP neural...
This paper presents the basic structure parameters of 800 kV DC composite insulator specimen and the pollution test scheme under whole voltage and whole structure dimension. The condition of 800 kV DC composite insulator pollution test under whole 800 kV voltage and whole structure dimension completed in STRI, which is completed first time in the world, is introduced. The study results indicate that...
This paper introduces the facing technical challenges and up to date research achievement of ?? 800 kV UHVDC transmission technology in China. The insulation coordination technology, external insulation technology, internal insulation technology and development of major ?? 800 kV UHVDC equipments are introduced emphatically. Most of these research items to be done are the first time in the world....
Directing to the low precision of single fault diagnosis method, a decision-level information fusion diagnosis system model was proposed to obtain more reliability and more accurate diagnosis, in which, the method based on the BP neural network was applied to the fault diagnosis firstly, and then the D-S evidence theory was utilized to partial fusions in diagnostic results, which was acquired in different...
The attribute reduction and value reduction of rough set were discussed in this paper. The discernibility matrix was extended to value reduction firstly and the attribute significance was redefined based on attribute dependence. An algorithm for classification rules extraction based on discernibility matrix and attribute significance is proposed, which keeps the same classification ability and the...
To design a streamlined network structure is a commonly used method for BP neural network to guarantee the neural network's generalization. Self- configuration algorithm deletes the redundant nodes of the hidden layer to achieve the optimized structure. But it isn't effective in solving the non-linear problem due to the linear regression theory basis. Thus, a self-configuring algorithm based on polynomial...
This paper presents the basic structure parameters of 800kV DC composite insulator specimen and the pollution test scheme. The condition of 800kV DC composite insulator pollution test under whole 800kV voltage and whole structure dimension completed in STRI, which is completed first time in the world, is introduced. The study results indicate that the linear relation between the pollution flashover...
This paper describes the SSTI study for Guizhou-Guangdong plusmn 500 kV DC transmission link being constructed in China Southern Power Grid. Well established methods which comprise the UIF analysis and the time domain simulation studies were adopted for the study. The UIF analysis provided hints for which generators SSTI must be studied in more detail. Time domain transient simulations were performed...
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