【正文】 高。所謂三沖量調節(jié)系統(tǒng)就是把給水流量 W，汽包水位 H，蒸汽流量 D 三個變量通過運算后調節(jié)給水閥的調節(jié)系統(tǒng)。如果水位設定值為 G，那么在平衡條件下應有 DDkWWk+HG=0 的關系式存在。若有一個或多個信號發(fā)生變化，平衡狀態(tài)被破壞， PI 調節(jié)模塊的輸出必將發(fā)生變化。鍋爐給水系統(tǒng)中還有一個比較重要的控制回路是給水壓力回路，因為汽包內壓力較高，要給鍋爐補水必須提供更高的壓力，給水壓力回路的作用是提高水壓，使水能夠正常注入汽包。汽包液位測量選用浮筒液位計。開車正常后波動范圍不大，可以不考慮。考慮到該廢熱鍋爐控制參數耦合小，流程簡單，產汽量也較穩(wěn)定，我 們從操作人員的操作中得到啟發(fā)，認為減少給水量的波動從而穩(wěn)定給水溫度成為該廢熱鍋爐液位控制的要點。這組 PID 參數可以使閥位波動幅度不大而回路有較快的跟蹤效果。以汽定水＋液位前饋比值控制方案調試投運簡單方便，投運后經負荷擾動 (產汽量變化 )、液位擾動 (排污量變化 )實驗，抗擾動性能良好，投運以來運行平穩(wěn)，達到工藝要求。 液位范圍（ %） 45 45~46 46~47 47~48 48 ~ 49 流量系數（ t/h） 液位范圍（ %） 49~51 51~52 52~53 53~54 54~55 55 流量系數（ t/h） 0 4 永宏 PLC PID 控制系統(tǒng)分析 帶 PID 控制功能的 FATEK 可編程控制器 PID 控制及其控制器或智能 PID 控制器 (儀表 )已經很多，產品已在工程實際中得到了廣泛的應用，有各種各樣的 PID 控制器產品，作為國產 PLC 企業(yè)，永宏電機股份公司一直致力于 PLC 的研究開發(fā)工作，帶 PID 控制功能的 FATEK 可編程控制器 (PLC)就是利用其閉環(huán)控制模塊來實現鍋爐汽包液位的 PID 控制，在異常情況下，如液位偏離正常值較大時，通過 PLC 控制系統(tǒng)控制，可以快速恢復水位，保證鍋爐的安全穩(wěn)定運行。 汽包水位 PID 控制設計優(yōu)點 (1) 減少干擾對主回路的影響，可由副回路控制器予以校正。 實際 PLC 的控制程序采用主副回路進行串級控制，即主回路的輸出做為副回路的設定值，經副回路輸出作用于被控對象。典型的閉環(huán)回路程控示意圖如圖 5 示。雖然微分項有上述優(yōu)點，但因其對輸出量的貢獻相當靈敏， 大部分的應用不必使用微分項而將 Td 設定為 0。它主要是依據系統(tǒng)的數學模型，經過理論計算確定控制器參數。三種方法各有其特點，其共同點都是通過試驗，然后按照工程經驗公式對控制器參數進行整定。 (2) 僅加入比例控制環(huán)節(jié)，直到系統(tǒng)對輸入的階躍響應出現臨界振蕩，記下這時的比例放大系數和臨界振蕩周期 。 5 結束語 由于 采用了 PLC 進行控制，系統(tǒng)功能完善，結構先進合理，能耗小，擴展靈活，便于維護，并且可靠性高，而且還極大地提高了企業(yè)的生產效率和經濟效益。 But the water level excessively low can destroy the soft drink circulation, is serious when causes the explosion of a boiler, therefore the boiler steam drum water level must strictly control. In order to guarantee the boiler to produce stable, reliable and the economical movement, we designed use the performance to be advanced the boiler PID automatic control system which forever great automatic equipment and so on FBsPLC, frequency conversion velometer, puter application will pose. This control system through examination water vapor pressure, temperature, movement physical quantity and so on steam drum fluid position, in movement process entire automatic control, has guaranteed the industry boiler security stable highly effective movement. 2 industries boilers related craft introduction The steam boiler is the factories and mines important power equipment, its duty is the supplies qualified stable steam, satisfies the load the need. Therefore, boiler production process each main parameter all must strictly control. But holds the very great proportion using the afterheat gas as the heat change medium afterheat boiler in the nation, its energy conservation falls consumes the effect especially to be obvious. Some chemical plant sulfuric acid afterheat boiler is the furnace gas which es out using the ebullition stove (mainly is SO2) the hyperpyrexia, takes it as the heat change object, through afterheat boiler vice midproduction pressure steam for each production branch factory use, also has guaranteed the production need, also had achieved the energy conservation falls the goal which consumes. The boiler is a more plex controlled member, provides the qualified steam for the guarantee to meet the load need, if the necessary design control system must satisfy each main craft parameter the need. Afterheat boiler technical process like chart 1 shows: Chart 1 afterheat boiler flow chart 3 controls difficulties analysis The boiler puter control is a new technology which the recent years developed. It is the microputer soft, the hardware, the automatic control, the boiler energy conservation and so on several technical in close integration with product, as the boiler control device, its primary mission is guaranteed the boiler the security, is stable, the economical movement, reduces operator39。3%. Chart 4 realtime fluids positions record curve 4 forever great PLC PID control system analysis brings PID the control function the FATEK programmable controller PID control and its controller or intelligent PID controller (measuring appliance) already very many, the product actual center obtained the widespread application in the project, has various PID controller product, took the domestically produced PLC enterprise, forever the great electrical machinery jointstock pany continuously will devote to the PLC research development work, will bring PID the control function the FATEK programmable controller (PLC) will be uses its closedloop control module to realize the boiler steam drum fluid position PID control, in unusual situation, when the fluid position deviation normal value will be bigger, through the PLC control system control, will be allowed fast to restore the water level, will guarantee the boiler the security stable movement. When the water monitor and the host vapor temperature control has the contradiction, may act according to the contradictory principal aspect to carry on two coordination controls. It contains for the water flow control return route and the steam drum water monitor return route two control loops, in the essence is the steam current capacity forward feed and the water level current capacity cascade system position pound control system. When steam current capacity change, in the boiler steam drum water monitor system may rapidly change the water volume for the water flow control return route to plete the coarse adjustment, then pletes the water level again by the steam drum water level regulator the thin accent. steam drums waters level PID control design merit (1) reduces the disturbance to the host return route influence, may adjust by the vice return route controller. (2) because the vice return route existence reduced the phase lag, thus improved the host return route speed of response. (3) has a better robustness to the control valve characteristic change. (4) the vice return route may defer to the host return route the demand to the object implementation accuracy