A Simulation Study on Boiler Fault Diagnosis Expert System

The boiler is one of the key parts of power station. Monitoring the operation of the boiler automatically, continuously and accurately is very important. In case of malfunctions, an expert system might be helpful to find the sources of faults, and thereafter will assist the operator to act correctly and to prevent the fault from further development.In this paper, a simulation study of an expert system, which can diagnose the running faults of boiler system, is conducted. Shallow and deep two-layer knowledge base structure is used in this two layers of knowledge base. So. this kind of expert system can overcome the disadvantages of the old types of expert systems, which are only able to deal with experience rules base.A simulator of power boiler is used for the research on fault diagnose expert system. This boiler simulator gives all necessary information for the diagnosis. The knowledge base of expert system is built in hierarchies, so the speed of reasoning may be invreased. After the reasoning the

Construction of Network Fault Simulation Platform and Event Samples Acquisition Techniques for Event Correlation

Event correlation is one key technique in network fault management. For the event sample acquisition problem in event correlation, a novel approach is proposed to collect the samples by constructing network simulation platform. The platform designed can set kinds of network faults according to user's demand and generate a lot of network fault events, which will benefit the research on efficient event correlation techniques.

Fault Ride-Through(FRT)Behavior in VSC-HVDC as Key Enabler of Transmission Systems Using SCADA Viewer Software

The world’s energy consumption and power generation demand will continue to rise.Furthermore,the bulk of the energy resources needed to satisfy the rising demand is far from the load centers.The aforementioned requires long-distance transmission systems and one way to accomplish this is to use high voltage direct current(HVDC)transmission systems.The main technical issues for HVDC transmission systems are loss of synchronism,variation of quadrature currents,amplitude,the inability of station 1(rectifier),and station 2(inverter)to either inject,or absorb active,or reactive power in the network in any circumstances(before a fault occurs,during having a fault in network and after a fault cleared),and the variations of power transfer capabilities.Additionally,faults impact power quality such as voltage dips and power line outage time.This paper presents a method of overcoming the aforementioned technical issues using voltage-source converter(VSC)based HVDC transmission systems with SCADA VIEWER software and dynamic grid simulator.The benefits include having a higher capacity transmission system and proposed best method for control of active and reactive power transfer capabilities.Simulation results obtained using MATLAB validated the experimental results from SCADA Viewer software.The results indicate that the station’s rectifier or inverter can either inject or absorb either active power or reactive power in any circumstance.Also,the reverse power flow under different modes of operation can ride through faults.At a 100.0%power transfer rate,the rectifier injected 775.0 W into the network.At a 0.0%power transfer rate,the rectifier injected 164.0 W into the network.At a-100.0%rated power,the rectifier injected 1264.0 W into the network and direction was also changed.

Fault simulation in ultrahigh voltage substation

Ultrahigh voltage(UHV)and extra-high voltage(EHV)have been widely used in power system,so the requirement for technology of operation management,as well as the accident analysis and disposal are more pressing.Based on the theory of Newton-Laphson power flow method,this simulation system imitates the primary device and secondary circuit,together with the normal,the abnormal and accidents in operation.Through simulation in various situations,it validates that this design is capable of simulating the complicated faults in UHV and EHV accurately and in real time.In addition,it can analyse and dispose them efficiently.

Fault Diagnosis for Non-linear System Based On Adaptive Fuzzy System

Although lots of valuable results for fault diagnosis based on model have been achieved in linear system, it is difficult to apply these results to non-linear system due to the difficulty of modeling the non-linear system by analysis. Adaptive Fuzzy system provides a way for solving this problem because it can approximate any non-linear system at any accuracy. The key for adaptive Fuzzy system to solve problem is its learning ability, so the authors present a learning algorithm for Adaptive fuzzy system, which can build the system's model by learning from the measurement data as well as experience knowledge with high accuracy. Furthermore, the experiment using the learning algorithm to model a servo-mechanism and to construct the fault diagnosis system based on the model is carried out, the results is very good.

基于FCM flow的小规模数字电路芯片测试

随着芯片工艺的不断演进,数字芯片的规模急剧增加,测试成本进一步增加。目前先进的DFT技术已应用于大规模SoC芯片的测试,包括扫描路径设计、JTAG、ATPG(自动测试向量生成)等。但对于一些小规模集成电路,插入扫描链等测试电路会增加芯片面积并增加额外的功耗。对于这种芯片,功能case生成的pattern可用于检测制造缺陷和故障。因此,需要一些方法来验证覆盖率是否达到了目标。Verisium manager工具依靠Xcelium的故障仿真引擎和Jasper功能安全验证应用程序(FSV)可以解决这个问题。它为ATE(自动测试设备)pattern的覆盖率分析提供了一个新的思路。

Accelerated Techniques in Stem Fault Simulation

In order to cope with the most expensive stem fault simulation in fault simu-lation field, several accelerated techniques are presented in this paper. These techniques include static analysis on circuit structure in preprocessing stage and dynamic calculations in fault simulation stage. With these techniques,the area for stem fault simulation and number of the stems requiring explicit fault simulation are greatly reduced, so that the entire fault simulation time is substantially decreased. Experimental results given in this paper show that the fault simulation algorithm using these techniques is of very high efficiency for both small and large numbers of test patterns. Especially with the increase of circuit gates, its effectivenbss improves obyiously.

Parallel Critical Path Tracing——A Fault Simulation Algorithm for Combinational Circuits

Critical path tracing,a fault simulation method for gate-level combinational circuits,is extended to theparallel critical path tracing for functional block-level combinational circuits.If the word length of the hostcomputer is m,then the parallel critical path tracing will be approximately m times faster than the originalone.

Deductive Fault Simulation Algorithm Based on Fault Collapsing

The true value simulation is necessary in the critical path tracing fault simulation algorithm.The critical and non-critical inputs can be known after the number of controlling and non-controlling inputs and the criticality of output of every gate are determined.Single output region(SOR)is defined for non-critical lines,so many other non-critical lines can be obtained before fault simulation.Then deductive fault simulation algorithm is used to compute the fault list for every possible critical line from bottom to top,which can greatly decrease the length of fault list and simulation time.The cross-section is defined to reduce the storage space.The experimental results are given at the end of the paper.

Efficient RT-Level Fault Diagnosis

Increasing IC densities necessitate diagnosis methodologies with enhanceddefect locating capabilities. Yet the computational effort expended in extracting diagnosticinformation and the stringent storage requirements constitute major concerns due to the tremendousnumber of faults in typical ICs. In this paper, we propose an RT-level diagnosis methodology capableof responding to these challenges. In the proposed scheme, diagnostic information is computed on agrouped fault effect basis, enhancing both the storage and the computational aspects. The faulteffect grouping criteria are identified based on a module structure analysis, improving thepropagation ability of the diagnostic information through RT modules. Experimental results show thatthe proposed methodology provides superior speed-ups and significant diagnostic informationcompression at no sacrifice in diagnostic resolution, compared to the existing gate-level diagnosisapproaches.

Fault Diagnosis of Physical Defects Using Unknown Behavior Model

A new fault model, called the X-fault model, is proposed for fault diagnosisof physical defects with unknown behaviors by using X symbols. An efficient X-fault simulationmethod and an efficient X-fault diagnostic reasoning method are presented. Fault diagnosis based onthe X-fault model can improve the accuracy of failure analysis for a wide range of physical defectsin complex and deep submicron integrated circuits.