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1、 蒸汽发生器水位控制蒸汽发生器水位控制中英文资料外文翻译文献中英文资料外文翻译文献Research on Fuzzy Control for Steam Generator Water LevelI. INTRODUCTIONThe steam generator is one of the main devices in PWR nuclear power plant, in order to ensure the safety of nuclear power plant during operation; the steam generators water level must be
2、controlled in a certain range. When the nuclear power plant is running, as the steam flow or the water flow changing, the amount of boiling bubbles in the steam generator will change due to local pressure or temperature change, the instantaneous water level showed “false water level” phenomenon . Th
3、e existence of “false water level” made it difficult to control the water level. The introduction of feed-forward control to the traditional single-loop PID control can, in a certain extent, overcome the “false water level“ phenomenon. But the conventional PID control method in the process of steam
4、generator water level control has some shortcomings. To the steam generator that has highly complex, large time-delay and nonlinear time-varying characteristics, the PID parameters tuning is a tedious job and the control effect is very poor. Furthermore, to achieve good control performance still as
5、conditions changing, it often needs to change the PID controller parameters. But the analog PID controller parameters are difficult to regulate online. Fuzzy control is a kind of nonlinear control strategy based on fuzzy reasoning, which express operating experience of skilled manipulation men and c
6、ommon sense rules of inference through vague language. Fuzzy control do not need to know precise mathematical model of controlled object, is not sensitive to the change of process parameters, is highly robust and can overcome non-linear factors, so, fuzzy control has faster response and smaller ultr
7、a- tone, can get better control effect. Based on understanding above, this paper design a steam generator water level fuzzy controller, the simulation shows that the controller has good control performance and practical value.II. DYNAMIC CHARACTERISTICS OF STEAM GENERATORThe transfer function of PWR
8、 steam generators mathematical model of the general form shows below:y(s)=GW(s)QW(s)+GS(s)QS(s) （1）where y is the steam generator water level; QW for the water flow; QS for the steam flow; GW (s) for the impact of the water flow to the steam generator water level; GS (s) for the effect of the steam
9、flow (load) to the steam generator water level.The balance of the steam generator water level is maintained through the match between the water flow and steam flow. The process that water level changes with the steam flow or water flow changing can be regarded as a simple integration process, but im
10、pact of the water flow and steam flow s change on water level is different.A. Dynamics Characteristics under Water Flow DisturbanceSuppose steam flow GS remains unchanged, and water flow GW step increases, on the one hand because the temperature of feed water is much lower than the temperature of sa
11、turated water in the steam generator, so that , when feed water entering, it will absorb a lot of extra heat, the vapor phase bubble contents will reduce, resulting in water level decreasing; on the other hand, the increase in water flow GW made it greater than steam load, and cause water level incr
12、eases linearly. Comprehensive two factors, after the step increase of the water flow, the water level rise has a time delay process, showing a down then up.B. Dynamic Characteristics under Steam Load DisturbanceSuppose feed water flow GW remains unchanged, and steam load GS step increases, on the on
13、e hand the water level will flow down because the steam flow rate is greater than the water flow rate. On the other hand, as the steam load increased, vapor pressure is reduced; the bubble volume on the liquid surface increases, causing the water level increased. Comprehensive two factors, after the
14、 step increase of the steam flow rate, the water level down has a time delay process, showing a up then down. The impact on the water level of water flow or steam flow stepping decreased has similar principle as above.As analysis can be seen as above, when the water flow or steam load change, the wa
15、ter level did not follow the change immediately, but there is an opposite process at first. This phenomenon is called “false water level“ phenomenon.III. DESIGN OF WATER LEVEL FUZZY CONTROLLERThe conventional PID controller has a poor control performance to the steam generator that exist “false wate
16、r level” characteristics, showing a greater overshoot in the tracking time. But a well-designed fuzzy controller is able to overcome the “false water level“ phenomenon, and has good control performance. A. Sstructure of Fuzzy ControllerThe structure showed in Figure 1.Fuzzy controllerK1valveGW(s)dx/dtK2GS(s)expected water leverStream flowWater leverwater floweec+-+-+Figure 1. Structure of steam generator water level fuzzy controllerChoose the water level error (e) and change rate
