1、英文原文Research on Fuzzy Control for Steam Generator Water LevelThomas Sowell Elgian Nuclear Research Centre SCKoCENBoer tang 200, 8-2400 Mol, Belgium (Received 15 March 2012) AbstractSince SG level control system is a highly complex, non-linear, time-varying and non-minimum phase system. The false wat
2、er level which is caused by the reverse thermal-dynamic effects known as shrink and swell effects, makes the SG water level process dynamics difficult to control. However, traditional PID methods cannot obtain satisfactory effects whose parameters are difficult to be adjusted online. Modern control
3、theory relys on controlled plants precise mathematics model completely. The fuzzy control technology doesnt rely on precise mathematics model and has excellent capability of adapting to the changed parameters. It is suitable for the SG water level control.I. INTRODUCTIONThe steam generator is one of
4、 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 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 bu
5、bbles in the steam generator will change due to local pressure or temperature change, the instantaneous water level showed “false water level” phenomenon. The existence of “false water level” made it difficult to control the water level. The introduction of feed-forward control to the traditional si
6、ngle-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 generator water level control has some shortcomings. To the steam generator that has highly complex, large time-delay and nonlinear time-varying
7、characteristics, the PID parameters tuning is a tedious job and the control effect is very poor. Furthermore, to achieve good control performance still as conditions changing, it often needs to change the PID controller parameters. But the analog PID controller parameters are difficult to regulate o
8、nline. Fuzzy control is a kind of nonlinear control strategy based on fuzzy reasoning, which express operating experience of skilled manipulation men and common sense rules of inference through vague language. Fuzzy control do not need to know precise mathematical model of controlled object, is not
9、sensitive to the change of process parameters, is highly robust and can overcome non-linear factors, so, fuzzy control has faster response and smaller ultra- tone, can get better control effect. Based on understanding above, this paper design a steam generator water level fuzzy controller, the simul
10、ation shows that the controller has good control performance and practical value.II. DYNAMIC CHARACTERISTICS OF STEAM GENERATORThe transfer function of PWR steam generators mathematical model of the general form shows below: （1）Where y is the steam generator water level; QW for the water flow; QS fo
11、r 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 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 pr
12、ocess that water level changes with the steam flow or water flow changing can be regarded as a simple integration process, but impact 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,
13、 and water flow GW step increases, on the one hand because the temperature of feed water is much lower than the temperature of saturated 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 wate
14、r level decreasing; on the other hand, the increase in water flow GW made it greater than steam load, and cause water level increases 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 Chara
15、cteristics under Steam Load DisturbanceSuppose feed water flow GW remains unchanged, and steam load GS step increases, on the one 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 red
16、uced; the bubble volume on the liquid surface increases, causing the water level increased. Comprehensive two factors, after the 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 water level
