Research On Fault Diagnosis System Of Inverter Control Cards In A Nuclear Power Plant

In the field of nuclear power which our country develop in,inverters have played an irreplaceable role. They are widely used in 220 V AC uninterruptible power supply system called LNE(Nuclear power plant system coding, L represents behalf of the electrical system, N represents 220 V power supply, E represents the fifth 220 V power supply). Their security, reliability and economy in the power system are the foundations of the nuclear power plant for survival and development. And the core of the inverter working depends on the inverter control cards' quality. It requires maintenance staff to grasp inverter card fault diagnosis and processing technique, and to ensure the normal operation of power system and to prevent damage of inverter. Thus it is particularly important to avoid these failures cause major accidents and huge economic loss. A fault diagnosis of Inverter cards system can avoid the unplanned downtime of nuclear power plant. It can maximum limit the downtime, reduce equipment maintenance costs and prolong the life of generator sets. It provides a large number of valuable information for optimal use of generating set, so it reflects very high economic benefits.Inverter control cards working on 220 V AC uninterruptible power supply system in nuclear power plants which is called LNE is the main research of the thesis. Based on the results of fault diagnosis technology at home and abroad and the analysis of the status quo on inverter cards, a kind of intelligent fault mechanism analysis and diagnosis system which can powerfully provide functions of long-term continuous test, analysis and suitable simulation model on inverter control cards is developed.The main works and research findings in the thesis are as follows:1.After reviewing a lot of related literature on fault diagnosis technology and applications of nuclear power plants, and combining with the research status of nuclear power plant fault diagnosis at home and abroad, the main content of this thesis is brought out;2. Inverter card is analyzed from the perspective of analog circuit, digital circuit, and integrated fault diagnosis on system level. The hardware parts of inverter card is analyzed from the card function including grid frequency detection, inverter overload protection, inverter output voltage monitoring and ac power grid voltage monitoring, it analyses;3. Basis on the advantages of Pspice simulation software, a simulation model of inverter cards is built in Pspice simulation software. Normal condition or fault condition of running state on inverter cards are achieved by changing the simulation parameters, thus a simulation library of standard case and failure case and provides the basis for fault diagnosis is built providing the basis for fault judgment;4. On the basis of provision of the test case design from nuclear power, the test automation hardware system is designed. The method of cards signal acquisition is provided, the adapter of inverter cards is designed and the signal acquisition and processing functions are developed, supporting the function of inverter cards operation on device level;5. The overall design train of thought of fault diagnosis system on inverter cards is expounded, the feasibility design scheme of the software and hardware coordination is put forward and the software system is briefly showed.Nuclear power inverter control cards is the main research content of this thesis. The intelligent inverter control card fault mechanism analysis and diagnosis system is designed and the conclusion of fault diagnosis is finally achieved. At present, this system is used in actual condition, providing warning for inverter system in nuclear power plant and judging the fault type of inverter cards. This system can significantly reduce huge economic loss of the accidents caused by inverter failure downtime in nuclear power plant.