control loop foundation€¦ · title: control loop foundation author: terry blevins subject:...

Copyright © 2010 by ISA

+

Process

Feedback

Controller

Manipulated

Input

Disturbance

Input

Multi-loop Control - Feedforward Control


Information

needed to

Commission

Feedforward

L/L & DT

Measured

Disturbance (D)

Controlled

Parameter(C)Deadtime

Lead/Lag

+Dynamic

Compensation

Process

Feedback

Controller

Manipulated (M)

C

M

C

D

Feedforward Control Implementation


Measured Load

Disturbance

Controlled

Parameter

Manipulated

Input

∆CM ∆CL

∆M

∆L

Time(sec)

Tm Td

63% of

Change

63% of

Change

Measured Load

Disturbance

Controlled

Parameter

Manipulated

Input

Time(sec)

DT1 DT2

Commissioning Dynamic Compensation


TC

185

TT

185

50-200 DegF

TT

185A

Workshop – Feedforward Control


Secondary

Controller

Manipulated

Disturbance

Disturbance

Process 2Process 1

Primary

Controller

Cascade Control


Outlet Steam

Temperature

Controller

Attemp Outlet

Temp Controller

Spray Valve

Steam

generatedFuel

Source

Superheater

Process

Attemperator

ProcessOutlet Steam

Temperature

Steam

Temp

Superheater Tubes

Boiler Drum

Spray Valve

Attemperator

TT

186TT

187

Example – Boiler Steam Temperature


Cascade Control Implementation

Selecting

FRSI_OPT for

dynamic reset

in primary loop

and Use PV for

BKCAL_OUT in

secondary loop

can often

improve

dynamic

response.


Workshop – Cascade Control


Manipulated

Controller

Information Needed to Tune

Controllers

Override

Controller

<

Max Value

Process

Constraint

Override Control


White Liquor

Clarifier

SC

190

FY

190

FC

190

AC

191

FT

190

AT

191

<

Density

Example – Override Control


Override Control Implementation


Workshop – Override Control


Controller Process

One(1) Controlled

ParameterTwo(2) Manipulated

Parameters

FY

Disturbance

Override Control


Split Range Control Implementation


Splitter SP

0 1000

100

0

100

0

100

100

100

0

0

OUT_1

OUT_2

LOCK_VAL “holds ”

LOCK_VAL “is zero ”

OUT_ARRAY

0 100 0 100

IN_ARRAY

0 100 0 100

OUT_ARRAY

100 0 0 100

IN_ARRAY

0 40 35 100

OUT_ARRAY

0 100 0 100

IN_ARRAY

0 40 35 100

Split Range Setup


400# Header

1475# Header

Boiler

Turbo

Generator

FY

196

PC

196

PT

196

BA

Example – Split Range Control


Workshop – Split Range Control

TT

197

TC

197

HeaterCooler

FY

197

Steam

Cooling

Water

BA


pH Process

Fine Valve

Coarse Valve

I-Only Controller

SP= Target

Valve

Position

Time

pH

Fine Valve

Coarse Valve

Target Valve

Position

AT

201

AC

201

ZC

201

Valve Position Control


PID configured for I-Only control

Valve Position Control Implementation


Low BTU – Waste Fuel

HI BTU Fuel

Boiler

BTU Demand

ZC

205

FT

205A

FT

205B

FC

205

FY

205

Example – Valve Position Control


Small

Valve

Big Valve

FT

215

FC

215

ZC

215

Workshop – Valve Position Control


Input = SP or PV of

independent loop

SP

SP= (Ratio * Independent Loop Input )

FT

220

FC

220

FT

221

FC

221

RC

221

Ratio Control


Ratio Control Implementation


FT

230

FC

230

FT

231

FC

231

AC

232

AT

232

RC

231

Example – Ratio Control

In this example

the ratio setpoint

is adjusted using

feedback control

based on a

downstream

analysis of the

blended material


Static Mixer

Main Flow

Blend Flow

% Solids

FC

251

FT

250

FC

250

AT

252

AC

252

RC

251

FT

251

Workshop – Ratio Control

control loop foundation€¦ · title: control loop foundation author: terry blevins subject:...

Documents