Coordinated Master Control

TALCHER SUPER TPP STAGE - II (4X500MW) NTPC

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Write-up on CLCS – COORDINATED MASTER CONTROL

References: CLCS Document No.4330-405-PVI-P-016 I & C Device List Basic symbols for Control and Instrumentation Abbreviation

CLCS – COORDINATED MASTER CONTROL

DOC. No : D0T195-302-CJY-E00 NTPC REF DWG : 4330-405-PVI-P-016

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Write-up on CLCS – COORDINATED MASTER CONTROL

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OVERVIEW

The purpose of this document is to explain and describe the implementation of Coordinated Master Control and Boiler Master Control used in t his project.

2.0

COORDINATED MASTER CONTROL PURPOSE: The purpose of this controller is to provide Load Set Point to Boiler Master and Turbine Master as per Unit Master Output when they are in Coordinated mode; while taking into account the Temperature Margins of Turbine and the margins of Fuel Master/Air Master/Feedwater Controllers.

The controller also calculates the Unit Capability based on the availability of

auxiliaries of the unit and ramps down the Load Set Point at a pre-set rate when one of the auxiliary trips. The various auxiliaries whose status is being monitored are as follows: 

ID Fan



FD Fan



PA Fan



Primary/Secondary Air Pre Heaters



BCW Pump



Turbine



CEP Pump



CW Pump



Mills

FUNCTIONAL DESCRIPTION: Automation System Structure: The Automation of Coordinated Master Controller allows the Operator to set the Load Set Point from the MMI unit (OWS/LVS etc) of the DDCMIS or through Hand Manual Station located in the Central Control Room (CCR). It consists of Commands, Interlocks and Monitoring functions necessary to manage the system correctly. The operator can set the controllers in Cas/Man mode and vary the Unit Load SP.

OWS/LVS Operator Interface: The following operator interfaces based on OWS/LVS operations are available in CCR. 

To Set Unit Load SP.



Cas/Man Selection of controller.

UCP Mounted Operator Interfaces/Devices: 

Hand Auto/Manual station for Unit Master 3-CF-HK-8201. CLCS – COORDINATED MASTER DOC. No : D0T195-302-CJY-E00 CONTROL NTPC REF DWG : 4330-405-PVI-P-016

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Write-up on CLCS – COORDINATED MASTER CONTROL 

Window Annunciators (based on customer inputs)

Control Philosophy Unit Master Set Point comes from Load Dispatch Centre. The output of Unit Master Auto Manual Station is fed to a Ramp Generator. The Ramp Generator’s output Rate of Change limit is set after detecting the direction of change while checking the Boiler margins. If Boiler margin (i.e., Fuel/Air/Feedwater Controllers deviations are within limit in the intended direction of change) the Ramp Generator’s output is allowed to change at a preset rate. A correction is applied to the set point according to deviation of frequency through a summer. The output of the summer block is passed further on to a Ramp Generator through a Switch if CMC mode is selected. If Boiler Follow mode is selected the input to the second Ramp Generator is the Delayed Load Set Point of Turbine Controller. If the Boiler is in Manual mode, Actual Load is fed as the input to the second Ramp Generator. The above said switching function is achieved using a Switch Block. The second Ramp Generator output is ramped according to the Output rate of Change limit. The output rate of change limit is calculated according to the direction of change. The output is allowed to change according to a rate of change if direction blocking is not present in the desired direction of change. Change in any direction is allowed only if the deviation of the following controllers are within a predetermined limit. The controllers whose deviation is monitored when an increase in SP is desired are: 

Feed Water flow Control



Air Flow Control



Fuel Flow Control



PA Header Pressure Control

The controllers whose deviation is monitored when a decrease in SP is desired are: 

Feed Water flow Control



Air Flow Control



Fuel Flow Control

The rate of change of limit is the minimum of the following: 

Load Rate of Change limit set by the operator



The rate of change limit calculated by the Turbine Stress Evaluator(TSE) according to the

margin available in the direction of change desired if TSE influence is turned on. Otherwise a safety margin of 50% is considered. The direction of change is determined by comparing the difference between the input and output of the ramp generator with a direction specific numeric with a value of +1 or –1(adjustable). When the difference cross the limit the direction of change is sensed and the corresponding margin is selected. The upper limit of the Second Ramp Generator is the minimum of the following: 

Unit capability



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Max Load SP set by the operator.



Max Load permissible by TSE.

Unit capability is calculated according to the auxiliary equipment availability. All the auxiliary equipments mentioned in the beginning of this section are monitored continuously and unit capability due to the individual equipments are compared with the Load SP and the minimum is selected as the SP to the Unit Capability ramp generator. When any one of the equipment trips the SP to the Unit capability ramp generator comes down correspondingly. The output of the Ramp Generator is brought down by Runback action. The runback rate depends upon the equipment that tripped. Maximum load permissible by TSE is calculated by adding the Upper margin provided by TSE with Actual Load. The lower limit of the second Ramp Generator is the maximum of the following: 

Minimum Load SP set by the operator



Minimum Load Permissible by TSE.

Minimum Load permissible by TSE is calculated by subtracting the Lower margin provided by TSE from Actual Load. The output of the second Load Ramp Generator is passed on to the Turbine Load controller as Load setpoint after delaying the output (by using a second order delay element)and subtracting a value (bias due to Throttle pressure deviation when CMC mode is selected). The same output is fed as Feed Forward signal to Boiler Master after adding a bias due to Frequency Correction (if the Frequency influence is kept ON in EHTC) when the Boiler Master is in CMC mode.

Unit Load SP Generation control: (Refer dwg. 3CJY00_01,02,03,04) As explained above the controller calculates the Unit Load SP for Boiler/ Turbine. Functional Blocks used: CJY00_1C21: Unit Master Auto/Manual Station. CJY00_1C22:REGCALC BLOCK CJY00_1C23: SUMMER Block for adding Frequency influence. CJY00_1C24: SWITCH Block to switch between Load SP of Unit Master/Load

Reference (PRTD)/Actual Load according to the mode selected. CJY00_1P06: CALCULATOR Block to calculate the difference between the output and

input of the ramp generator. CJY00_1N56, CJY00_1N57: NUMERIC Blocks used to detect the direction of change. CJY00_1N51: NUMERIC Block to pass on Frequency deviation signal when the same is

not bad.



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Write-up on CLCS – COORDINATED MASTER CONTROL CJY00_1P01, CJY00_1P02, CJY00_1P03: GENLIN Block used to calculate the

correction factor due to frequency deviation. CJY00_2C21: RATIO Block used as ramp generator to limit the output rate of change

according to the TSE margin available. The Output High/Low limits are determined according to Unit capability , TSE margin and the Maximum/minimum limit set by the operator. CJYOO_2P01: LEADLAG Block to provide a second order delay to Unit Load SP

generated. CJY00_2N58: NUMERIC Block used to determine throttle pressure deviation. The

deviation of the Boiler master controller is selected and passed on according to the mode (CMC/Boiler Follow) mode selected. CJY00_2P02: GENLIN Block used to determine the influence of Throttle Pressure

deviation on generated Unit Load SP. CJY00_2N51: NUMERIC Block used to pass the bias due to Throttle pressure deviation

when CMC mode is selected. 4CJY00_2C22: SUMMER Block for calculating the Load SP to EHTC after taking into

account the bias due to Throttle pressure deviation. CJY00_02.CALCULATOR : CALC Block used to determine the Feed forward signal to

Boiler master after taking into account the frequency correction signal. CJY00_2N52: NUMERIC Block to pass on Frequency correction signal when Frequency

influence is turned ON in EHTC. CJY00_3P01, P02, P03, P04, P05, CJY00_4P01, P02: CALC Blocks used to determine

unit capability set point by selecting the minimum capability of the auxiliary devices as the final setpoint. CJY00_3N51 TO CJY00_3N73 & CJY00_4N51 TO CJY00_4N57: NUMERIC Blocks

used to determine individual equipment capability according to availability of the equipment. If the equipment is ON then the capability of the equipment is passed on as the value of the numeric by the corresponding logic otherwise zero is passed on. CJY00_4N59 TO CJY00_4N68: NUMERIC Block for determining the individual

auxiliary equipment’s runback rate. The rate is kept as zero until the equipment’s capability is more than the unit SP. Once the equipment’s capability comes below unit SP a predetermined runback rate is passed on. 3CJY00_04.RUNBACK : HILOAVG Block used as high selector to select the highest of the

available run back rates. •

CJY00_3C21: RATIO Block used as ramp generator for determining unit

capability. During runback the output is ramped according to the predetermined rate of the equipment due to which the runback is initiated. CLCS – COORDINATED MASTER CONTROL


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Write-up on CLCS – COORDINATED MASTER CONTROL •

CJY00_4N69, CJY00_4N70: NUMERIC Blocks used by the operator to set

Maximum/ Minimum Load SP. CJY00_4P05: CALC Block used to calculate the upper and lower limit of Unit SP ramp

generator.

Protection and Interlock: The unit master is forced to Manual if any one of the following signals is present 

ADS Fault



RUNBACK is in action



RUNUP is not permitted



RUNDOWN is not permitted.

Hand Operated A/M stations for Boiler Master: (Refer dwg. 3CJY00_06) AutoManual stations located in UCP has the facility to take the controller individually to Manual mode and manipulate the outputs. This is redundant to the facility available in OWS. This is achieved using calculator and Logic blocks. Functional Blocks used: 3CJY00_06.UCP: CALC Block – Increment and decrement command from UCP Auto

Manual stations are taken as inputs and the calculated value is written back to Unit Master Auto Man Station.

3.0

BOILER MASTER CONTROL PURPOSE: The purpose of this controller is to maintain Throttle Pressure of Main Steam at Turbine inlet around the Set Point. Boiler Master determines the Set Point for Air Master and Fuel Master when they are in Cas Mode. The Throttle Pressure SP is operator set when the Boiler Master SP is in Fixed SP mode and is dependent on either Boiler Load Index or Actual Load (Pre Set) when the SP is in Sliding Pressure Mode.

FUNCTIONAL DESCRIPTION: Automation System Structure: The Automation of Boiler Master allows the manipulation of Boiler Demand from the MMI unit (OWS/LVS etc) of the DDCMIS or through Hand Manual Station located in the Central Control Room (CCR). It consists of Commands, Interlocks and Monitoring functions necessary to manage the system correctly. The operator can set the controllers in Auto/Man mode and vary the recirculation flow.

OWS/LVS Operator Interface: CLCS – COORDINATED MASTER CONTROL


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Write-up on CLCS – COORDINATED MASTER CONTROL The following operator interfaces based on OWS/LVS operations are available in CCR. 

Adjusting Boiler Demand.



Selection of Transmitters



Cas/Man Selection of controller.

UCP Mounted Operator Interfaces/Devices: 

Hand Auto/Manual station for Boiler Master 3-CF-HK-8202.



Window Annunciators (based on customer inputs)

Main Steam Throttle Pressure at Turbine Inlet: (Refer dwg. 3CJY00_01) Three independent measurements are available. The functional block MIDOF3 calculates the middle value. The operator has the facility to select between these 4 values (3 transmitters and Mid value) via GUI. Functional Blocks used: 3CJY00_01. 3TX_1: HILOAVG block for operator selection.

Control Philosophy The Set Point is either determined by the operator or depends on Boiler Load Index depending upon the mode that is selected. If fixed SP mode is selected from MMI the SP is operator determined. When the same is not selected the SP is determined based upon either Boiler Load Index or Actual MW. Selection between the two is preset. The Boiler Master can be operated in two different modes. When the Boiler Follow mode is selected the controller with a Feed Forward signal based on either Boiler Load Index or EHTC Load Set Point is selected. The selection between the two-feedforward signals is preset. When Coordinated Mode is selected the controller with Unit Load SP generated by Coordinated Master as the Feed Forward Signal is selected for control. When Manual mode is selected or when Run Back in Action the Boiler Master A/M station trips to Manual mode. When ‘Run Back in Action’ signal is present Turbine Follow mode Signal is automatically selected and the Unit capability comes down to match the available capability. This signal is factored (MW to Fuel Ratio) and given as Boiler Master output to the downstream controller viz., Fuel Master and Air Master signal respectively. This will result in reduction of Steam Generation to match the available Unit Capacity. The turbine controller switches to initial pressure mode and starts controlling the Throttle pressure simultaneously. In order to provide for tracking during manual mode a switch is provided. This switches the Boiler Master demand to actual Fuel Flow (in terms of Percentage) when Fuel Master controller is not in Cas mode. With the tracking option ON, the Boiler Master Auto Manual Station Output is made to track Actual fuel flow (Percentage value) when Fuel Master is in Manual mode. When Fuel Master switches back to Cas mode a bump is avoided as Boiler Master A/M output was tracking actual Fuel Flow. Operator can select the various modes of operation (Manual mode, Turbine CLCS – COORDINATED MASTER CONTROL


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Write-up on CLCS – COORDINATED MASTER CONTROL Follow mode, Boiler Follow mode and Coordinated Mode) provided the enabling conditions are present and tripping conditions are not present.

Boiler Master Control: (Refer dwg. 3LCY02_02) Functional Blocks used: CJY00_2C28: RATIO Block for operator set Throttle Pressure Set Point. CJY00_2C29: SWITCH block for switching between Fixed SP mode and sliding

pressure mode. 3CJY00_2C23.PIDA, 3CJY00_2C24.PIDA: PIDFF Blocks, which control the Throttle

Pressure, according to SP during Coordinated Mode and Boiler Follow Mode respectively. CJY00_2N56: NUMERIC Block to select BLI/EHTC setpoint as Feed Forward signal

for Boiler Master when the Boiler Follow mode is selected. CJY00_2C25: SWITCH Block to switch between the two controllers during Boiler

Follow mode and Coordinated mode respectively. CJY00_2C26: AUTOMAN Block that acts as Boiler Master Auto Man station. CJY00_2C27: SWITCH Block to switch between Boiler Master Output and Fuel Flow. CJY00_5D41, D42, D43, D44: DIGCOMP Blocks to select Manual Mode, Turbine

Follow Mode, Boiler Follow Mode and Coordinated Mode respectively. CJY00_2N56: NUMERIC Block for determining the bias to be added to Operator set

Throttle Pressure Set Point to calculate HPBP Set Point. 3CJY00_02.CALCALCULATOR_1: SUMMER Block for calculating the HP Bypass

Set Point.

Hand Operated A/M stations for Boiler Master: (Refer dwg. 3CJY00_06) AutoManual stations located in UCP has the facility to take the controller individually to Manual mode and manipulate the outputs. This is redundant to the facility available in OWS. This is achieved using calculator and Logic blocks. Functional Blocks used: 3CJY00_06.UCP: CALC Block – Increment and decrement command from UCP Auto

Manual stations are taken as inputs and the calculated value is written back to Boiler Master Auto Man Station.

Protection and Interlock: The Boiler Master Auto Man Station is tripped t o Man when any of the 

Transmitters’ deviation high or all three transmitters signal bad.



Man Mode is selected from MMI.



Run Back in Action.



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NTPC


Turbine follow Mode is selected.

The Auto Man Station is forced to CAS mode when Boiler Follow mode selection condition is present. The output of Auto/Man Station is forced to a value proportionate to Unit Capability when Runback is in Action.

Legend for Control Schemes: AI

- Analog Input

AO

- Analog Output

DI

- Digital Input

LB

- Logic Block

DO

- Digital Output

NM

- Numeric

NN

- Node Number

FL

- Flag

MM

- Module Number

SS

- Slot Number

Abbreviation List: MID OF 3

-Median value selection

HILOAVG

-Selection of average or Operator select

PID

-Proportional +Integral +Derivative control

RATIO

-Ratio control

AUTOMAN

-Auto/Manual station

SUMMER

-Summing of inputs

GENLIN

-Function Generator

SWITCH

-Switching between inputs (S1,S2,S3,S4)

CALC

-Calculator

OPLOLM

-Output Low Limit

OPHILM

-Output High Limit

ESWMAN

-Switching externally (through logic block) to Manual mode

ESWCAS

–Switching externally (through logic block) to Cascade mode

ESWAUTO

-Switching externally (through logic block) to Auto mode

ESWENBST

-Enabling Mode change

Tag. XXXX

-Refers to the internal parameter of the tag

PVFL

-Digital Status



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Coordinated Master Control

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