cmc
DESCRIPTION
coordinated master controlTRANSCRIPT
CMC
(COORDINATED MASTER CONTROL)
Prepared by:
SUKHAMOY ROY. SR.SUPDT.(C&I).
& C&I-BOILER-II GR.
CMC ensure proper coordination between Auxiliaries, boiler and turbine to attain efficient and safe running of the plant. In thermal power units the turbines are fast responding components& boilers are having transport lag & thermal inertia Hence delayedly respond with variation in command. Turbine will be able to control the load or th.pre. quickly by changing the position of control valves. The other parameter are to be controlled by boiler master. The mode of operating the units as follows.
(1)CMC – coordinated mode (2)BOILER follow mode- Boiler follow turbine(3)Turbine follow mode- Turbine follow Boiler
(constant Pr. Mode)(4)RUNBACK MODE.
1) CMC:
Basically to control internal parameter’s of unit like (1) M S Pressure, (2) Load. Also to coordinate sensitive turbine and slow response of boiler auxiliaries, Good for network and Unit stability. Both Boiler and Turbine control ON Auto.
2) BFM:
Boiler follow turbine. Turbine on Load control- Boiler ON Auto-control pressure with BLI as feed forward. MW demands are met by Turbine firstly and lesser importance to unit stability.
3) TFM:
Turbine follow Boiler. Boiler Master on manual control. Pressure control. Turbine maintains pressure by varying MSCV ,Unit load depends on steam output from boiler Best for unit stability
Definitions:
RUNBACK MODE.RUNBACK MODE.
under runback conditions the firing for the boiler must be reduced to preset values, as close as possible to the tolerable limits. Therefore the swings of firing rate caused by the action of the PID controller must be avoided. As consequence of this condition the system has to switched to pure feed forward to control where the firing rate set point is directly proportional to load capability signal. To avoid any mismatch between steam production of the boiler and the turbine load turbine has to be switched to initial pressure control.
04) RUNBACK:
In R/B mode boiler controls give command in proportion to unit capability. Turbine – Pre. Control. R/B mode sets in automatically.
05) BOILER MASTER:
Basically a pressure controller
FEED FORWARD SIGNAL
GNI OUTPUT - CMC
BLI - B.F.M
PRTD - T.F.M
GET BYPASSED - R/B
F/F Pre. Set point Actual pressure +
BM
06) G N I :
Control tracking generator or set point control module. Generates increase/decrease rate.
Target to GNI:
CMC : Load dispatch center or unit- master [frequency
corrected]
BFM : Boiler demand (BM O/P)
TFM : Actual Load.
R/B : Unit capability.
07) UNIT CAPABILITY:
Capability to produce MW at that instant, W.C signal depends on the number of auxiliaries in service and their contribution is expressed as MW signal, which they can support.
08) FGMO:
Free Governing mode of operation Intro duce critical external parameter i.e. freq. of network to our control system. To ensure stability of network or grid it is necessary to have frequency regulation in CMC/EHC. But frequency is network parameter, which cannot be controlled by few units in the network. Total disturbance in network will be passed on to the units having regulation by the many units do not have regulation.
09) CMC TABLE ModeBoiler
controlsTurbine controls
InputTo BoilerControls
Feed Forward
InputTo turbine
control
BFMThrottle
PressureMW
Pressure error
Steam Flow[BLI]
MW error(Load controller
active)
CMC Pressure MWPressure
errorMW errorGNI O/P
MW error(Load controller
active)
TFM
MW & Pressure
[Manual at KORBA]
Throttle- pressure(Pressure
controller active)
Pressure error
PRTD Turbine load set
point
Pressure error
RUNBACK
Produces steam as per unit
capability
Throttle- pressure(Pressure
controller active)
UNIT Capability
Signal
BMBypassed
Pressure error
BOILER FOLLOW BOILER FOLLOW MODEMODE
1. Turbine on load control2. Boiler master on Auto-controls throttle steam Pressure with steam flow as feed forward. Varying fuel I/P (firing rate) in the furnace.
In this mode boiler has to supply the steam for whatever load has been set from Turbine desk. In this way if the throttle steam reaches a limit (10 kg below the set throttle steam Pr.) “limit Pr. Engaged” condition comes and load would be scarified to maintain/restore the throttle steam Pr.
MW SET PT.
G
MW
F
T
+ -
PR. B
FUEL FIRING DEVICE
+ -U
PID PI
F
P-
BOILER FOLLOW MODE
SELECTION OF BOILER FOLLOW MODE ( BFM)SELECTION OF BOILER FOLLOW MODE ( BFM)
1. Put air control on auto (at least one FD fan)
2. Put feeders speed control on auto after varying fuel master(FM) output and making feeder speed controller error zero.
3. Vary Blr. Master O/P so that FM error becomes zero. Then put FM on auto.
4. Make throttle pr. Set point and actual pr. Difference zero.
5. Put BM on auto.
If unit in turbine follow or coordinated mode change over to boiler follow occurs under following condition :-
turbine goes to manual because of any reason or operator action
Pr CMC - Pr Lim > 60MW
TURBINE FOLLOW TURBINE FOLLOW MODEMODE: - : -
1. Boiler manually controlled2. Turbine master On Auto -controls throttle
steam Pre. (With steam flow as feed forward) by varying load.
In T.F.M Pr. Controller comes into picture and the throttle Steam Pre. Varies the opening of MSCV to maintain the set throttle steam Pre.
MW SET PT.
PI
G
NF
T
+PR. SET PT.
B
PI
FUEL FIRING DEVICE +
-
-
-P
TURBINE FOLLOW MODE
SELECTION OF TURBINE FOLLOW MODE ( TFM)SELECTION OF TURBINE FOLLOW MODE ( TFM)
1. Boiler master on manual.
2. Throttle pressure deviation zero.
3. Turbine in auto.
4. Press. Turbine flow push button along with manual release on CMC desk and turbine goes to initial pressure mode from LMT mode by itself.
5. Now load set point can be changed by varying the boiler master manually.
+
+
Tracking integrator
PPID
PI
GENBOILER
Pressure Set Signal
Steam PR.
TURBINE CONT.
Guidance load signal
Boiler Controller
Throttle Pr. error
Freq. Deviation correction
Logic Unit Load Capability
Min
Boiler Turbine
Unit Target Load
Min Load Rate (Set)
Permissive Load Rate form turbine stress evaluator (ESE)
Runback
+
+
-
+
± +
-
Turbine Controller
MW
CMC LOOP basic
PR.CORRECTION CKT.
CMC controls the plant treating boiler and turbine as a unit. It aims is to generate desired ‘MW’ O/P through coordinate regulation of boiler I/P & O/P (turbine I/P). Turbine must not increase load without taking firing /boiler inertia in consideration.CMC coordinate sensitive turbine & slow response boiler & Auxiliaries. IN CMC Boiler master on Auto
Turbine master on Auto Unit master - Receiving load demand from ALDC or Manually
from desk.In cmc sets the MW set point which will be pursued by boiler master by taking throttle pressure error as final trimming input signal. Turbine will control the MW by taking mw error as input. Th.pre. error will not be effecting the the mw till it is beyond limits. Boiler master will change the air & fuel to provide the desired steam. The respond will be slow when compared to turbine response. So it may be reemphasized that this mode of operation gives maximum stability to the units with optimum response taking boiler & turbine as a unit.Pressure correction curve is basically a bridge between the slow boiler & fast responding turbine control. Performance of CMC largely depends on the proper tuning of the curve. Tuning of the curve varies with boiler & fuel .
Pressure Correction in CMCUnder normal operating conditions including small load
(pressure) variation boiler and turbine are controlled independently as per set point from GNI. Any unbalance in power generation and power consumption due to frequency variation in FGMO , throttle pressure may increase or decrease which may cause dangerous condition in the boiler.
If DP (Set throttle pre.- Actual throttle pre.) variation goes below set point ( - ve pressure deviation) , boiler storage capacity is used. However, any large variation in throttle pressure shall restrict the Turbine output till the Boiler has produced the additional output to match the increased demand. Similarly in case of +ve pressure deviation turbine output will increase.
MW
2 Kg - DP
15MW
1 Kg 15MW
1 Kg 2 Kg + DP
Note:- Note:- THROTTLE PRESSURE (DP) correction starts at +/- 1Kg and acts upto +/- 2Kg. It will add or subtract +/- 15 MW to the GNI output, thereby generating pressure corrected GNI output to EHC.
+
+-
MaxnMin
P
Th.Pre. Set.Pre
F/F
Pre. Correction
Adder
Adder
O/p
K F
Min
UnitMaster
GNI
MAX
MIN
Boiler master PI+D
Delay
Frequency connected GNI O/P
Frequency & Pr.Connected GNI O/P to EHC
P
+---
+ +
Air master Fuel master
FREQUENCY INFULENCE ON CMC
1.5 %
MW
39923012
10MW
20MW
TSE upper margin
TFM
MIN
P
P
MAX
MIN
CMC
F/D
TFM
PRTD
UnitMaster
MAX
MIN
MAX
MIN
LOADUNIT
+
+-
MIN
MAX
MIN
Delay
Boiler master PI+D
Air master Fuel master
BFM
Set.Pre Th.Pre
TFM
BFM
P
MIN
UNIT load rate
Runback limit
TSE lower margin
PR (CMC set
Pt to turbine)BLI P
F(x)
UNITCOORDINATER
GNI
Runback in action
Capability
LDC
PULV A -J
Frequency influence
PA FAN A
CMC
BFM
PA FAN B
UNIT Capability
LIMITING BLOCK
Turbine load limiter
Actual MW
Boiler demand
Target of unit
D action
load
+ + -
+
+ +
+
-
CMC LOOP ST#II KORBA
Load Reference
FrequencyInfluenceON
Pressure Correction
Load Limiter
FrequencyUnloadingCharacteristic
Load controller
TSE Influence
+
+
+ MIN
+
-
Max / Min.Limiter
Max Min
Load Setter
GNI
Delay
Boiler Master
( f ) Load
Actual Pressure
Throttle Pressure Set.
+
+
+ +
++
++
+
-
EHC
Load
25MW
40MW
0. 2HZ
0. 125 HZ
Freq
CMC LOOP
X Y P AB
P
P
Y1Y2
Y2Y1
28.6%85.7%
3X1.01
X001 XM03 XP01 PT3 X001
CVCORRECTED COAL FLOW
A
B
TOTAL OIL FLOW
MW GENERATED
XP01
TOTAL COAL FLOW
-+
+-
+ +
B/M O/P AIR
MIN
FUEL MASTER
A B J
CV Correction loop manipulates the coal flow measurement signal by increasing or decreasing it, to show less coal is going when coal quality is bad and more when coal is good the effect is limited to 85% to 100% of actual coal flow
CV CORRECTION LOOP
Max
Max
XN01
XN01
P XP01
Max XN01MIN
AIR FLOWTOTAL
AIR FLOW
XN01
AIR FLOW DEMAND
PIR L
RS04OXYGEN MASTER
80%
+ +
HK7715D WY
Ua = Ui
20%
TOTAL FUEL FLOW BOILER DEMAND
( = 0..1)XM02
Ui
FDA FDB
AIR MASTER
TOTAL AIR FLOW
- +
O2 Correction loop manipulates the total airflow
measurement by increasing or decreasing O2 master to show
less air/more air is flowing. This influence is limited to 30% of the total air flow [Presently]
AIR MASTER LOOP
O2 TRIMO2 TRIM - -
A section station and a setter for oxygen set point are provided to achieve the desired excess air. If variable O2 set point (SP) is selected, set point is generated by a function generator which is a function of max ( air flow SP and total air flow). In other mode SP is set from UCB. O2 in flue gas is compared with this SP and error is fed to PI controller, output of which is limited between 0.8 and 1.2% of total air flow.
SELECTION OF CMCSELECTION OF CMC
1. Put air control on auto (at least one FD fan)
2. Put feeders speed control on auto after varying fuel master(FM) output and making feeder speed controller error zero.
3. Vary Blr. Master O/P so that FM error becomes zero. Then put FM on auto.
4. Make throttle pr. Set point and actual pr. Difference zero.
5. Put BM on auto.
6. Increase /decrease unit master output so that it becomes equal to actual load. (wait unit load set value and load value matches as shown in the CMC panel digital indicator).
7. Form TG desk put turbine control on auto.
8. Press coordinated push button along with manual release on CMC desk.
Controller
Mill PA Flow
+ -
FEED RATE
UCB Set Point
Max
HAD
CURVE GENERATOR Generator
MILL PA FLOW GENERATION CURVE
MILL PA FLOW AUTO SETTING
CURVE GENERATOR SETTINGS XU01 CARD
HAD SET POINT FOR PA FLOW AS PER FEED RATE
FEED RATE (T/H) MILL PA FLOW SETPOINT (T/H)
0 70
17.5 75
20 77
30 92.5
40 96.5
50 100
60 105
70 108
CURVE GENERATOR SETTING
7075
77
92.596.5
100
105108
0
20
40
60
80
100
120
140
0 17.5 20 30 40 50 60 70
FEED RATE(T/H)
MIL
L P
A F
LO
W S
ET
PO
INT
(T/H
)
SEC.AIR FLOW (L)
MAX
O O O
MAX
P
PI
RL
Y
+
PI
RL
Y
- <
F(X)
P
BIAS
O O O
+
PI
RL
Y
F(X) <
-
PIRL
OOO
+
Σ
Σ/n +
AW02 AW02
O2
-
O2
-
O2 PROBE (L) O2 PROBE (R)
FLUEGAS O2
A/M
MAX
~
Σ
ΣSEC.AIR FLOW (R)
PA FLOW FROM MILLS
ANY 6 MILLS
TOTAL FUEL FLOW
TOTAL AIR
GAIN CHANGE
MW AIR FLOW
A B C D E J
+ + - -P
20%+ +
80%
Ua= Ui X∞
( = 0.1)
RS04
AW02 AW02- -+ - + -
FD FAN B BLADE PITCH
FD FAN A BLADE PITCH
Y ActY Act
+- + -- +
AIR FLOW CONTROL SCHEME ( EXCESS AIR)
A/MA/M
THANK YOU THANK YOU