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Research On Fast Control Method In Digital Electric Hydraulic System Of Steam Turbine And Fault Diagnosis And Fault Tolerant Control

Posted on:2010-05-25Degree:DoctorType:Dissertation
Country:ChinaCandidate:X X LiFull Text:PDF
GTID:1118360275969985Subject:Mechanical and electrical engineering
Abstract/Summary:PDF Full Text Request
The steam valve regulating system of modern steam turbine unit has transmitted from mechanical hydraulic regulation to digital electro-hydraulic(DEH) regulatinon, which improve the quality of adjusting, realize the complex control algorithm, strengthen the system security and enhance the regulating quality of power and frequency. However, there is no fast control valving function in most DEH systems of our country. Fast control valving is an effective measure that kept the electric power system running stably. Especially when it is applied in area where the electric network structure is weak, the transient stabilization ability of electric power system can be enhanced obviously. In this paper, regulating system in 200MW steam turbine is studied. The protection principle of fast valving under the malfunction of electric network, devise of fast control system and optimization operation tactic are all analyzed and experiment research are made. At the same time, the faults such as interal leakage, plugging and jam in DEH system and fault tolerant control of the system are studied deeply. The chapters of the paper are arranged as following:In chapter 1, the related study background and significance of the subject are expounded. On the basis of referring to domestic and international associated documents, the research development and the current application situation of the regulating system in steam turbine are summarized. Characteristics and application of fast control system in steam turbine are introduced. Then the main problems in the study of the regualting system are analyzed. The main study work is proposed.In chapter 2, retrofit of regulating system from mechanical hydraulic control to elecro-hydraulic control is implemented and new type steam turbine fast valving mechanism is devised. The commonly used control rule of fast valving is analyzed. The operation principle and structure of steam valve is set forth. The forces received by valve are analyzed in detail.The retrofit of regulating system in 200MW reheated condensing steam turbine from mechanical hydraulic control to elecro-hydraulic control is implemented, based on which new type fast valving system is devised. There is function of both fast closing valve and fast opening valve.In chapter 3, the mathematic model of the whole fast valving system is built up and the simulation of and experiment are fulfilled. First the mathematic model of the system is given, providing theoretic basis for paper. With the use of software-AMESIM, the model of regulating system is built up. The factors influencing the performance of fast opening system is analyzed and the operation dead zone is studied, based on which optimization control tactic in dead zone is brought forward. The experiment platform of fast valving system is built up and test is realized.The simulation results and experiment results are compared, which validated the correctness of the devise.In chapter 4, the internal leakage in steam turbine electro-hydraulic system is studied. The reasons of leakage in system are analyzed. Several leakage fault mechanisms and their mathematic models are analyzed in detail. The problems of conventional diagnosis methods of internal leakage are given. The internal leakage of oil servo motor, regulating valve and servo-proportional valve are studied respectively. The changes of parameters including regulating time, oil pressure and so on are compared under the conditions of different internal leakage slit and flux. Besides, the influences of symmetrical and asymmetrical internal leakage on system are also compared. After simulation, characteristic table is given to diagnose internal leakage. In the end of this chapter internal leakage experiment is made to validate the analysis results.In chapter 5, the jam fault in manipulative mechanism of steam turbine regulating system and the plugging fault of servo valve in DEH system are studied. The structure of manipulative mechanism and the jam fault cause are both analyzed. Research is done about the particular jam fault caused by spring excursion and the theory formulas of spring excursion length are educed. Based on theory analysis and simulation three diagnosis methods are studied. The online output signals of DEH regulating system are analyzed in order to extract the fault characteristics of the servo valve directly. Based on simulation the characteristic table of the servo valve plugging is given. With characteristic parameters such as the displacement and the oil pressure, the duo-neural network is put forward to achieve an online diagnose on the plugging fault. Intelligent test and fault diagnosis system for servo valve in DEH system of steam turbine is developed, with which general characteristic analysis on common servo valve, servo-proportional valve and proportional valve can be fulfilled. The idea that static and dynamic characteristics of servo valve are analyzed once is advanced. For the first time cartridge valve is applied in servo valve test system to switch oil pipe. There are many advantages in the system such as full automation, fast response, great flux, and etc, with which test in GB/T 15623-1995 can be implemented. It plays an important role in repair and fault diagnosis of servo valve in power plant.In chapter 6, the fault tolerant control method of steam turbine based on multi-feedback is advanced. First the application situation of fault tolerant technique in steam turbine electro-hydraulic control system is introduced. Then the fault tolerant control regulating system based on displacement, flux and pressure feedback is devised. The fault diagnosis rules of sensors and fault tolerant control rules are put forward. The regulating performance under three closed loop control modes are compared based on simulation. Finally the experiment is carried out to demonstrate the feasibility of the design.In chapter 7, the major work of the study is summarized, and the conclusions and innovations of the study are elaborated. At the same time, future development is predicted in order to provide references for the further research on this project.
Keywords/Search Tags:steam turbine regulating system, digital electro-hydraulic control system, fast control mechanism, optimization operation tactic, fault diagnosis, internal leakage analysis, jam in manipulative mechanism, plugging fault in servo valve
PDF Full Text Request
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