Geh 6811
Geh 6811
Geh 6811
GEH-6811A
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Revised: 2012-05-31
Issued: 2011-10-11
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Salem, VA 241536492 USA
Contents
Chapter 1 OpFlex* Product Overview .................................................................................. 1-1
Terms..................................................................................................................................................... 1-2
DLN System Theory ................................................................................................................................ 1-2
DLN Modes ............................................................................................................................................ 1-3
DLN Split Control.................................................................................................................................... 1-4
GEH-6811A
Contents
Notes
Contents
All Load Cycle Control (ALCC) is a GE term for the application of MBC design to
heavy-duty gas turbine (GT) control as an upgrade to the traditional schedule-based control
approach. ALCC is not a stand-alone product but specifically applies MBC methodology
from full-speed no load to peak load. Prior to the development of ALCC-based products,
the MBC methodology was limited to loads corresponding to Dry Low NOx (DLN) Mode
6 and higher. The following GE OpFlex products use MBC methodology.
ALCC-based:
Cold Day Performance 3.x = AutoTune + removal of cold ambient Tfire suppression
9FA Start-up NOx = ETS + revised low mode DLN fuel split schedules
Cold Day Performance 2.x = DLN Mode 6 CC + removal of cold ambient Tfire
suppression
ALCC is the F-class control architecture for all future product development. Many future
software and hardware upgrades will require the application of ALCC.
This document primarily defines AutoTune 3.x. For further information on the ETS
system refer to GEH-6810, OpFlex Enhanced Transient Stability (ETS) for GE Gas
Turbines User Guide.
From a DLN perspective the design of the AutoTune 3.x and Cold Day Performance 3.x
products are identical. Therefore, all references to AutoTune technology also apply to the
Cold Day Performance product unless otherwise noted.
GEH-6811A
Product Description
1-1
Terms
The following terms are used throughout this document:
ALCC
ARES
CDM
CDP
CRT
DCS
DLN
ETS
FSR
GS
Gas Turbine
HMI
Human-machine Interface
LBO
Lean Blowout
MBC
Model-based Control
PAMB
PCI-based Acoustical Monitoring revision B Mark Ve/Mark VIe CDM I/O pack
TRT
VAMB
VPR
1-2
DLN Modes
To maintain operability across the GT cycle from part-speed acceleration to base load,
the fuel must be staged in the combustor. This is achieved by connecting the fuel nozzles
to different supply manifolds. For a DLN 2.6 combustion system these manifolds are
referred to as PM1, PM2, PM3 and quaternary. For a DLN 2.6+ system these manifolds
are diffusion, PM1, PM2 and PM3. The various combinations of active manifolds are
called DLN modes.
When multiple manifolds are active there must be a determination of the percentage of
fuel to send to each active manifold. This percentage is referred to as the DLN split or
the fuel split.
GEH-6811A
Product Description
1-3
1-4
GEH-6811A
Product Description
2-1
Notes
2-2
GEH-6811A
Product Description
3-1
Notes
3-2
GEH-6811A
Product Description
4-1
LBO Models
Two independent control loops are used to protect against combustion LBO. The GE
combustion laboratory was used to map out LBO at various cycle conditions. This data
was then fit into a model that captures the varying conditions experienced in the combustor.
The result is a boundary model that is programmed into the controller. AutoTune does not
allow the DLN fuel splits to move past this LBO boundary. Second, there is a control loop
based on measured combustion dynamics. If combustion dynamics approach a signature
that is indicative of LBO, the system adjusts DLN splits to avoid operation in this region.
4-2
Emissions Models
AutoTune contains an emissions model for both NOx and CO. These models attempt to
re-create the physics of the actual reactions that occur in the combustor. They were first
developed for the DLN 2.6 combustor through years of data collection and processing.
Once the general techniques were established these same models were then used in the
DLN 2.6+ system with system specific alterations. The emissions models require unit
specific tuning to account for unit-to-unit variation since there is no active emissions
feedback. When properly tuned to a specific unit, these models achieve the same order
of magnitude of accuracy as a typical industrial emissions sensor. Once this relationship
is established for a given set of hardware it does not change. This allows the AutoTune
product to run for years without requiring any manual retuning of the emissions model. It
also allows for advanced diagnostic analysis and troubleshooting in the case of a hardware
problem. Only when the combustor or other flange-to-flange hardware is changed is
a DLN retune required.
Dynamics Models
Each of the combustion dynamics tones that GE controls has its own model. These models
are programmed into the controller and calculate the combustion dynamics based on
measured unit parameters as well as ARES outputs. Similar to the NOx model, they are
tuned to be specific to the unit hardware.
The combustion dynamics models are continuously adjusted based on the inputs from the
CDM system. Similar to the emissions models, the use of a model avoids the time lag
that is associated with collecting and processing combustion dynamics levels. It also
allows the system to continue operation based on the models alone, without relying on the
secondary tuning to the CDM system in the case of a CDM system fault or failure.
Both the CDM system measured
and the model calculated
dynamics are available to
the operator though the HMI
AutoTune screens.
AutoTune requires a redundant CDM system to avoid single point failures. The CDM
system software uses various I/O health processing checks that remove bad CDM sensors
from the system. Not all sensors are required to be healthy for use in AutoTune control.
The AutoTune system cannot control each combustion can, so the intent of using the CDM
feedback is to understand the average behavior of the system. This design accommodates
many faults before it is completely removed from active control in AutoTune.
GEH-6811A
Product Description
4-3
Notes
4-4
Fuel flexibility
Transient capability
Fuel flexibility AutoTune enables the combustor to adapt to varying fuel constituents
to maintain acceptable parts life, output, and emissions targets. Past simulation and field
testing has demonstrated gas turbine operability under a wide range of fuel composition
conditions (as indicated using the Wobbe Index calculation). This is achieved while
observing emissions targets, and maintaining stable control of all relevant boundaries.
Heated fuel units can also recover fuel temperature to rated temperature, increasing
performance. This temperature may be lowered or varied on some GE frame sizes to
accommodate fuel variation.
Seasonal retune elimination In addition to handling varying fuel compositions, the
real-time calculation process and independent control loops of the system allow it to
adapt to changes in the airflow properties as well as fuel flow. This allows the unit
to instantly tune to the ambient conditions, be it a weather pattern change or an inlet
conditioning system.
Reduced overall dynamics The hardware should experience lower combustion
dynamics amplitudes over its lifetime. This is because the system is free to optimize the
dynamics when not otherwise constrained.
Real-time emissions target adjustments The AutoTune product includes a NOx slider
bar. This slider is a bias that allows the end user to adjust the internal AutoTune NOx
control target. The default target for the 7FA.03 DLN 2.6 GT is 8 ppm. The slider bar
allows the end user to adjust the system to account for small deviations that can exist
between the AutoTune NOx model and the site emissions reporting instrumentation.
For NOx, the allowable bias range is -1 to 5 ppm. The bias input from the slider bar
is rate limited, so any slider bar changes take 1-2 minutes to ramp to the desired bias.
Since emissions control is prioritized over dynamics control, the NOx slider bar can be
used to reduce combustion dynamics in some cases. Increasing the NOx bias potentially
allows the control loops to further minimize dynamics. This can be a worthwhile tradeoff,
especially for units with flexible NOx permits or SCR systems.
Transient capability The AutoTune product is engineered and tested with ETS. It
offers GEs most advanced technology to survive grid or other rapid transients that can be
imposed on the GT by operability demands or external sources.
GEH-6811A
Product Description
5-1
Disabling AutoTune
The AutoTune product cannot be disabled though the HMI. The system automatically
disables AutoTune if it detects a problem with the 96 GN DP transducers. This is
preferable to a unit trip. However, running on the fixed DLN split schedules may be
inappropriate for the given fuel, hardware, or ambient conditions.
Note If Autotune is disabled, it is possible that the unit may blow out or experience
high emissions or dynamics.
5-2
GEH-6811A
Product Description
6-1
Notes
6-2
Selecting any Combustion Can data from this screen displays the following window,
providing detailed can-level fault information. This can be useful when troubleshooting
the CDM system.
GEH-6811A
Product Description
7-1
In addition, clicking the CDM Fault Tree button on the Combustion Data screen
displays the following window, illustrating how the CDM faults feed into the system
lockout/trouble alarms. This can also be useful when troubleshooting the CDM system.
7-2
Control DLN
The existing DLN screen has been modified for AutoTune to include readings from the
fuel system manifold pressure sensors (96GN sensors). Each of the TMR sensors displays
on this screen.
Note The following screen is DLN 2.6 specific; the DLN 2.6+ screen has a different
manifold and TMR configuration.
GEH-6811A
Product Description
7-3
Notes
7-4
Attention
Additional CDM system Alarm
information can be found
in GEK 116769, Control
Description and Operation of
Combustion Dynamics Monitor
(CDM) Enhancements.
If 96GN sensors fault, fail degraded biases applied to machine boundary targets as
appropriate to accommodate these failures.
If all FPGN sensors are unavailable on an operating fuel circuit, AutoTune will be disabled
and the unit will slew out of AutoTune and run on fixed splits.
If combustion high dynamics exceed limits for a predetermined amount of time, the
unit will perform a load runback. The control has taken the necessary action to protect
the machine from an undesirable mode of operation. Enter a PAC case to alert product
service. If an immediate reloading of the unit is required, monitor the dynamics closely
using the Combustion HMI screen.
For detailed alarm descriptions and signals, refer to the unit specific Control Specification
provided under MLI A010 and A210 with each unit.
GEH-6811A
Product Description
8-1
Notes
8-2
GE Energy
1501 Roanoke Blvd.
Salem, VA 241536492 USA
1 540 387 7000
www.geenergy.com