PPT《Case Study #1: Boiler Control锅炉控制》

Case Study #1: Boiler Control锅炉控制 Lei XIEInstitute of Cyber-Systems & Control, Zhejiang University, Hangzhou, P.

R. China Contents Process Diagram and Control Problems of Boiler (锅炉设备的生产流程与控制问题)Characteristic Analysis & Three-element Control for Drum Level (汽包水位特性分析与三冲量控制) Cross-limiting Air/Fuel Ratio Combustion Control (双交叉空燃比燃烧控制) Simplified Process Diagram of a Boiler Main equipments ? Decompose the process into several subsystems ? Boiler Control Problem System decomposition: (1) drum-level control;

(2) combustion control;

(3) steam-temperature control. Select the best pairing of MVs & CVs ? Drum-level Control Problem Controlled variable: drum level, in H (s)Manipulated variable: feedwater flow, in F (s)Main disturbances: Steam flow, in D (s) Please explain the reason why it is a difficult problem Drum-level Characteristics Disturbance pathcharacteristic (Why?) Control pathcharacteristic (Why?) Models ? Non-minimum phase Characteristics There will be a zero in right side of the complex plane if The process will be called "non-minimum phase system (非最小相位系统)" One-element (单冲量) Control Simple PID Control Two-element (双冲量) Control Problem discussion: (1) Point out the kind of control methods ?(2) Obtain control diagram of the scheme.(3) Select the controller action, the symbol and the value of C2, if the valve is a fail-open valve and C1=1. Three-element (三冲量) Control Control Diagram ? Two Simplified Connections of Three-element Systems Which differences between two connections ? Combustion Control Problem MVs and CVs Pairings: Flue gas →Furnace pressure, Air → Excess Air (O2% in flue gas), Fuel → Steam pressure Simple Control Schemefor Combustion Control Existing main problem ? Cross-limiting Air/Fuel Ratio Combustion Control Advantage:Decoupling designProtect against excess of fuel under all conditions Analyze the control scheme Feedforward/Feedback Control for Furnace Pressure Analyze its design principle Steam-temperature Control Scheme Which kind of control methods ? Problem Discussion 《工业过程控制工程》思考题与习题 23-2~23-4, P.420 Exercise 9.1 To control drum level, the three- element control scheme shown in left figure is common used. If the feedwater valve is failed-open, then (1) describe the complete control diagram, and note the inputs and outputs for each block;

(2) determine the symbol and the value C1, C2, C3 as well as the action of level controller LC. Next Topic: Distillation Control(精馏塔控制) Description of Distillation Column Distillation Control ObjectivesSteady-state CharacteristicMeasurement of CompositionDecomposition of Control ProblemBasic Control Schemes Next Topic: Problem Discussion CVs (被控变量):P, LD, LB, TR/xD, TS/xB MVs (操作变量):D, B, L, QH, QC, DG DVs : F, xF, TF To design your multi-loop control system to satisfy the above requirements and reduce interaction