WHAT IS A CONTROL SYSTEM ? WHAT IS A CONTROL SYSTEM ? WHAT IS A CONTROL SYSTEM ?
WHAT IS A CONTROL SYSTEM ?
•
• A SYSTEM WHICH AUTOMATICALLYA SYSTEM WHICH AUTOMATICALLY
TAKES CORRECTIVE ACTION TO
TAKES CORRECTIVE ACTION TO
ELIMINATE ANY ERROR IN THE
ELIMINATE ANY ERROR IN THE
PROCESS AND KEEPS THE DESIRED
PROCESS AND KEEPS THE DESIRED
OUTPUT WITHIN PERMISSIBLE LIMITS.
OUTPUT WITHIN PERMISSIBLE LIMITS.
•
• A CONTROL SYSTEM CAN BE AN OPENA CONTROL SYSTEM CAN BE AN OPEN
LOOP OR CLOSED LOOP, DEPENDING
LOOP OR CLOSED LOOP, DEPENDING
UPON THE ERROR DETECTION
UPON THE ERROR DETECTION
MECHANISM.
TYPES OF CONTROL SYSTEM TYPES OF CONTROL SYSTEM
• AN AUTOMATIC CONTROL SYSTEM IS USED TO MAINTAIN ITS OUTPUT WITHIN DESIRABLE LIMITS BY MEANS
OF A CONTROL ACTION.THE ERROR SIGNAL IS USED TO ACTUATE CONTROL ACTION THROUGH CONTROLLER.
THESE CONTROL ACTIONS ARE :
• PROPORTIONAL
• DERIVATIVE
• INTEGRAL
CONTROL LOOPS IN SERVICE AT UNCHAHAR
• PI CONTROLLER:-1.DRUM LEVEL 2.FUEL MASTER 3.AIR MASTER 4.MILL AIR FLOW
5.PA HEADER PRESSURE
6.FEEDER SPEED OR COAL FLOW • PI-PI CONTROLLER
1.FURNACE DRAFT 2.FRS DP
3.SH/RH CONTROL • PID
CONTROLLER:-1.MILL O/L TEMP. CONTROL 2.COMBUSTION CONTROL
COMBUSTION CONTROL COMBUSTION CONTROL
THE OBJECTIVE OF ANY CONTROL
SYSTEM
IS
TO
MONITOR
AND
CONTROL
VARIOUS
PARAMETERS
AND INTER LINKED SYSTEMS WITHIN
THE
DESIRED
LIMITS.IT
WOULD
OTHERWISE BE VERY DIFFICULT OR
VIRTUALLY IMPOSSIBLE TO MONITOR
& CONTROL
SO MANY DIFFERENT
PARAMETERS
AND
SYSTEMS
IT IS A CONTROL LOOP SYSTEM WHICH
CONTROLS
AND
CREATES
AN
ENVIRONMENT INSIDE FURNACE TO
ENSURE CORRECT AMOUNT OF AIR
WITH RESPECT TO THE ADMITED COAL
SO
AS
TO
COMPLETELY
BURN
ALL THE FUEL.
INSUFFICIENT AIR RESULTS IN UNBURNT
FUEL WHILE EXCESS AIR INCREASES
THE QUANTITY OF WASTE HEAT.
COMBUSTION CONTROL COMBUSTION CONTROL
ADVANTAGE ADVANTAGE
DISADVANTAGE DISADVANTAGE
RATIO OF FUEL TO AIR / FEEDER SPEED IS IN ITSELF VARIABLE AND DEPENDS ON MANY FACTORS SUCH AS EFFICIENCY OF MILL CONTROL SCHEME ,PERCENTAGE OF ASH IN FUEL AND EFFIENCY OF THE MILL CONTROL SYSTEM.
WITH A SINGLE COMMAND i.e.VARIATION OF THROTTLE PRESSURE FROM TURBINE DESK ONE CAN CONTROL TOTAL AIR FLOW IN THE FURNACE ,TOTAL FUEL IN THE FURNACE AND THEIR COORDINATED CONTROL TO MAINTAIN AIR FUEL MIXTURE AND THROTTLE PRESSURE.
COMPONENTS OF COMBUSTION CONTROL COMPONENTS OF COMBUSTION CONTROL
THIS LOOP CONTAINS TWO MAJOR SECONDARY LOOPS:
AIR
AIR MASTER MASTER AND FUEL MASTER FUEL MASTER
MASTER CONTROL OF THESE TWO
B PID CONTROLLER MIN MAX MAX MIN F(X)
MASTER PRESSURE CONTROLLER MASTER PRESSURE CONTROLLER
THROTTLE PRESSURE SP THROTTLE PR. ACTUAL 75 % 40 %
TO AIR MASTER TO FUEL MASTER
ACTUAL TOTAL FUEL ACTUAL TOTAL AIR BTU A
AIR FLOW MASTER AIR FLOW MASTER
F(x) PI ACTUAL AIR FLOW TO FD FAN VANES O2 TRIM A FROM MASTER CONTROLLER 70 % TO 110%
FUEL MASTER FUEL MASTER PI ACTUAL FUEL FLOW B FROM MASTER CONTROL
50 100 0 100 140 180 BTU IN %
C
O
A
L
F L
O
W
TOTAL AIR AT 800 T/HR BTU CURVE BTU CURVE RELATION BETWEEN BTU AND FUEL/ AIR RATIO 0 % = 0.5 50 % = 0.7 100 % = 0.9
CCS-CCS- CO-ORDINATE CONTROLSCO-ORDINATE CONTROLS
AN INTEGRATED APPROACH TO CONTROL FINAL OUTPUT OF THE TURBO-GENERATOR i.e. LOAD, KEEPING ALL OTHER IMPORTANT PARAMETERS LIKE THROTTLE PRESSURE , TOTAL FUEL FLOW , TOTAL AIR FLOW i.e. COMBUSTION INSIDE FURNACE ,OXYGEN AND FURNACE PRESSURE WITHIN LIMITS.
CCS-CCS- CO-ORDINATE CONTROLSCO-ORDINATE CONTROLS
THE OBJECTIVE OF THIS CONTROL SYSTEM IS TO OPERATE THE TURBINE ,GENERATOR AND BOILER AS AN INTEGRATED UNIT.BY THE COORDINATED ACTON IS MINIMUN INTERACTION BETWEEN CONTROL VARIABLES OF UNIT GENERATION , STEAM PRESSURE ,FLUE GAS OXYGEN,FURNACE
DRAFT AND STEAM TEMPERATURE BY
APPROPRIATE SIMULTANEOUS OPERATION . MANIPULATED VARIABLES OF FUEL,FEEDWATER , AIR AND TURBINE GOVERNER
THE CCS PROVIDES FOUR DIFFERENT OPERATING MODES
CCS CCS
CCS IS DESIGNED FOR FOUR DIFFFERENT MODE OF OPERATIONS DEPENDING UPON THE STATUS OF THE TWO MAIN UNITS i.e. TURBINE AND BOILER.
AT ANY ONE POINT OF TIME ONLY ONE MODE CAN BE SELECTED.
MANUAL MODE
TURBINE FOLLOW MODE BOILER FOLLOW MODE CO-ORDINATE MODE MANUAL MANUAL MANUAL MANUAL AUTO AUTO(REMOTE) AUTO TURBINE BOILER AUTO(REMOTE)
MODE SELECTION LOGIC: CO-ORDINATE MODE PR. CONTROL BY BOILER
MW CONTROL BY TURBINE BASED ON SP FROM CMC .
BOILER FOLLOW MODE PR. CONTROL BY BOILER
MW CONTROL BY TURBINE BASED ON LOCAL SP(EHTC)
TURBINE FOLLOW MODE PR. CONTROL BY TURBINE MW CONTROL BY BOILER MANUAL MODE MW CONTROL BY TURBINE PR. CONTROL BY BOILER CCS CCS
CCS CCS
COORDINATE MASTER CONTROL:
IN THIS MODE OF OPERATION BOTH TURBINE AND BOILER REMAINS IN AUTO . M W IS CONTROLLED BY EHTC AND THE STEAM PRESSURE i.e. MS THROTTLE PRESSURE IS CONTROLLED BY BOILER FIRING RATE CONTROL.
THE SET POINT FOR EHTC IS GENERATED FROM CMC CONSOLE.
BOILER FOLLOW MODE:
IN THIS MODE OF OPERATION TURBINE REMAINS IN LOCAL i.e. LOAD IS CONTROLLED BY EHTC SET POINT FROM TURBINE CONSOLE.WHEREAS BOILER FUNCTIONS TO MAINTAIN THE THROTTLE PRESSURE.EHTC LOAD SET POINT IS USED FOR FEEDFORWARD TO BOILER MASTER.
BOTH CMC AND BFM HAVE THE ADVANTAGE OF QUICK RESPONSE TO LOAD CHANGES AND BETTER CONTROL
CCS CCS
BOILER MASTER :
THIS CONTROLLER CONTROLS COMBUSTION IN THE FURNACE AND MAINTAINS THROTTLE PRESSURE BY VARYING FIRING RATE. SLIDING PRESSURE MODE CHECKES BOILER LOAD INDEX FOR THE CALCULATION OF THROTTLE PRESSURE SET POINT.
TURBINE FOLLOW MODE:
IN THIS MODE OF COTROL STEAM PRESSURE IS CONTROLLED BY TURBINE AND LOAD IS CONTROLLED BY BOILER
TFM WILL AUTOMATICALLY SELECTED WHEN RUNBACK OCCURS AND SYSTEM IS NOT IN MANUAL MODE.
OR
THROTTLE PRESS TX OK
AND
AIR MASTER AND FUEL MASTER AUTO. TURBINE IN LOCAL MANUAL MODE SELECTED R S OR 2 3 4 1 MA
MANUAL MODE SELECTION MANUAL MODE SELECTION
TFM MODE SELECTION TFM MODE SELECTION
AIR MASTER AND FUEL MASTER AUTO.
AND
AND
OR THROTTLE
PRESS TX OK AND
RUNBACK IN ACTION R S OR 1 3 4 2 TF BFM CMC TFM RELEASE TUR.IN LOCAL PR DEV >< +-1.5%
BFM MODE SELECTION BFM MODE SELECTION AND AND R S OR 1 2 3 BF 4 BFM CMC TFM RELEASE
TUR.IN LOCAL AIR MASTER AND FUEL MASTER AUTO.
EHC LOAD >< +-2.4%
CO-ORDINATE MODE SELECTION CO-ORDINATE MODE SELECTION
AND AND R S OR 1 2 4 3 BFM CMC TFM RELEASE TUR.IN LOCAL EHC LOAD >< +-2.4%
AIR MASTER AND FUEL MASTER AUTO.
C O
RUNBACK IN ACTION CMC BLOCK CMC BLOCK DIAGRAM DIAGRAM
ACTUAL TURBINE LOAD EHTC LOAD SP MAX UNIT LOAD SP CMC CONSOLE MINIMUM LOAD SP MIN SELECTOR SELECTOR LOAD INTEGRATOR (SWI) SELECTOR SELECTOR II ND ORDER DELAY
LOAD SET POINT TO
TURBINE CONTROL EHTC
FEEDFORWARD TO BOILER MASTER MAXIMUM LOAD SP MAXIMUM TURBINE LOAD (FROM TG) 2 1 EHTC LOAD SP CMC SELECTED SEL. 2 2 2 ACTUAL TURBINE LOAD MANUAL MODE SELECTED SEL. 2 1 SELECTOR OR BFM AND TFM SEL. 2 1 SEL. 2 2 1
ACTUAL THROTTLE PRESSURE CMC SEL SELECTOR 1 THROTTLE PRESSURE SP CMC CONSOLE 2 INT (SWI) FKG BLI SLPR. MODE SELECTED SEL. 2 ADDER MUL PID CONTROLLER ADDER FKG SELECTOR SELECTOR SEL. 2 SEL. 2 1 1 2 2 OR RA CMC BFM EHTC LOAD SP LOAD SP FEEDFORWARD TO BOILER MASTER UNIT CAPABILITY RUNBACK IN ACTION A CMC BLOCK CMC BLOCK DIAGRAM DIAGRAM
AIR MASTER AIR MASTER DIAGRAM DIAGRAM A FKG MAX INT (SWI) MAX MUL FKG FKG PIR TOTAL FUEL ACTUAL BLI O2TRIM RAISE LOWER AIR FLOW MASTER SP
TOTAL AIR FLOW ACTUAL
SAD 1A/1B
PIR MAX ADS FKG BLI
TOTAL SA FLOW TOTAL PA FLOW A MIN PIR ADDER FKG TOTAL FUEL ACTUAL MEF MCD MAB MILL BIASING END BIASING PIR
MAIN AIR DAMPER
FUEL MASTER FUEL MASTER
DIAGRAM DIAGRAM
THROTTLE PRESSURE VARIATION VS THROTTLE PRESSURE VARIATION VS
LOAD CHANGE LOAD CHANGE -1% 1% -1..5% 1..5% 3..2% -3..2% THRT. PR.VARIATION IN % (100% =200KG/CM3) L O A D IN % 100% = 250 MW
0 – 2.0 KG/CM3 NO VARIATION IN LOAD
2.0 – 2.6 KG/CM3 0-3.675 MW / KG/CM3
2.6 – 3.0 KG/CM3 3.675-6.72 MW / KG/CM3
THROTTLE PRESSURE VARIATION VS THROTTLE PRESSURE VARIATION VS
LOAD CHANGE LOAD CHANGE
TO MAINTAIN LOAD AS PER THE AVAILABLE CAPACITY OF THE UNIT AND TO SAVE UNIT FROM TRIPPING RUNBACK
SYSTEM IS INITIATED.EACH AUXILLIARY WHICH IS USED FOR KEEPING THE RESPECTIVE PARAMETERS WITHIN RANGE HAS CERTAIN CAPACITY UPTO WHICH IT CAN BEAR LOAD.THIS LIMIT IN TURN DEFINES THE BOILER LOADING CAPACITY i.e. HOW MUCH LOAD CAN BE GENERATED WITH THAT
AVAILABILITY.
ALL THESE LIMITS ALONG WITH THE MAXIMUM LOAD i.e. 100% ARE THEN COMPAIRED BY A MINIMUM BLOCK ,THE OUTPUT OF WHICH THEN DEFINES THE UNIT CAPABILITY.
RUNBACK SYSTEM: RUNBACK SYSTEM:
RUNBACK SYSTEM: RUNBACK SYSTEM: M I N I M U N UNIT CAPABILITY UNIT CAPABILITY ID FAN LIMIT(130 %) FD FAN LIMIT(130%) PA FAN LIMIT(130%) FUEL LIMIT(130%)
BFP LIMIT(100%) (DELAY 3SEC)
TURBINE / LSR LIMIT(60%)
MAX LOAD (100 %)
THESE LIMITS ARE AS FOLLOWS FOR THE RESPECTIVE AUXILLIARIES:-1. ID FAN 65% EACH 130 % FOR TWO FANS
2. FD FAN 65% EACH 130 % FOR TWO FANS
3. PA FAN 65% EACH 130 % FOR TWO FANS4.
4. MILL 65% EACH 130 % FOR TWO MILLS
5. TURBINE TRIP/LSR OPER. 60% 100% FOR NORMAL RUNNING
FINAL CMC DEMAND i.e. BOILER MASTER DEMAND CONTINUOUSLY CHECKS UNIT CAPABILITY AND DEPENDING UPON THE UNIT CAPABILITY THE FINAL OUTPUT IS GOVERNED.
FOR EX. IF 80 % IS THE NORMAL BOILER O/P DEMAND AND UNIT CAPABILITY IS 100% AND SUPPOSE ANY AUX. SAY ID FAN TRIPS THEN BOILER MASTER O/P WILL BECOME (80 X 65 =52). RUNBACK SYSTEM: RUNBACK SYSTEM: SELECTOR FINAL BOILER MASTER OUTPUT TO AIR AND FUEL MASTER UNIT CAPABILITY BOILER MASTER DMD RUNBACK IN ACTION 2 1 SEL 2
S R AND RUNBACK SEL RUNBACK IN SERVICE MANUAL MODE RUNBACK IN ACTION
MANUAL MODE SEL
RUNBACK SYSTEM: RUNBACK SYSTEM:
WHENEVER THESE CONDITIONS FULFILL “RUNBACK IN ACTION” ALARM WILL APPEAR AND TURBINE CONTROL WILL TRANSFER INTO PRESSURE CONTROLLERFROM LOAD CONTROLLER AND TFM OF CMC WILL ACTIVATE.
