POWER June 2011 - 41

INSTRUMENTATION & CONTROL
ments full-plant equipment models and can
be " tuned " to the latest plant conditions.
The tool allows the user to accurately forecast
maximum power that can be generated
from the two power blocks under a variety of
operating conditions. To forecast the maximum
power generation possible, the user
must input the following parameters:
■ CT inlet pressure drop
■ CT exhaust pressure drop
■ Ambient temperature
■ Ambient pressure
■ Relative humidity
■ Cooling water inlet temperature
■ Current level of CT degradation
The CT inlet pressure drop, exhaust pressure
drop, and current CT degradation can
be obtained from the online EfficiencyMap
system. The user can also estimate the maximum
power generated by each block under
" new and clean " conditions.
K-Power generates the forecast for the
next 24 hours using these tools and then
sends the forecast to KPX based on the lowest,
highest, and average expected ambient
temperatures. After receiving the load profile
from K-Power, KPX sends the load profile
for the next day back to K-Power by 18:00
hours. The load profile is then converted to
a continuous AGC signal, which MVC uses
to control plant output by manipulating the
power setpoint of the individual CTs.
Commissioning New Controls
A long-term commissioning plan was established
at the project kickoff. A complete team
charter was also developed to define the roles
and responsibilities of the GE engineers and
K-Power staff. The MVC commissioning
plan had five stages:
1. Instrument input/output checkout
2. DCS level configuration checkout
3. Plant step testing and APC controller
tuning
4. Model building and implementation
5. Site acceptance test
The start-up team included GE commissioning
engineers working on DCS-level
configuration checks to ensure that the plant
was well protected during all anticipated operating
scenarios and that switching between
different control modes (such as APC control,
automatic, and manual functions) was
bumpless. Additional configuration changes
were made to ensure that the regulatory controllers
defaulted to safe mode in the event of
failure of the supervisory computer.
Before plant step tests, all DCS level control
loops were checked to make certain all
the basic regulatory controllers were properly
tuned. These were not just APC-related
loops but also other loops that improved unit
stability and ensured smooth plant operation.
The GE engineer developed the DCS logic
changes, and the K-Power DCS engineer approved
the logic changes and implemented
the logic changes on site during scheduled
outages. GE and plant engineers tested the
logic changes thoroughly before the power
blocks were returned to operation.
Full involvement of plant staff, especially
the operations staff, is critical for the success
of any APC implementation. During the step
testing phase of MVC commissioning, for
example, plant operators were fully involved.
Continuous and frequent interaction between
the GE engineering team and operating personnel
allowed the GE engineering team
to learn about the intricacies of plant operations.
In turn, the plant operators learned
more about multivariable control.
Operator Training
The plant operators are the primary users of
the APC system, and proper operator training
is a critical component of a successful APC
project. Formal operator training consists of
a systematic and comprehensive training program,
which is normally held after commissioning
and prior to the site acceptance test.
At K-Power, operators were trained on APC
fundamentals as well as hands-on usage of
the APC system during project implementation
and post-commissioning.
The APC training material covered basic
process control concepts, DCS-based
advanced control concepts, multivariable
control concepts, and the MVC system. Human
machine interface and K-Power-specific
control strategies and operational procedures
were also discussed.
During the hands-on APC system training,
the GE engineer explained the control
strategies specific to this project and how
the multivariable controllers move manipulated
variables to satisfy setpoint variables
and constraint variables under different scenarios.
Operators were trained how to activate
and deactivate MVC, how to perform
minor troubleshooting, and how to handle
system start-up and shutdown. An operator's
manual was provided at the end of the training.
An ongoing supporting services agreement
ensures that the benefits derived from
the MVC, EfficiencyMap, and what-if tools
continue into the future.
Post-APC Performance
The MVC was successfully commissioned at
K-Power in October 2007. Thanks to a userfriendly
operating interface, a single-window
philosophy of operation, and proper training,
operators have readily accepted the APC
system. This system has achieved measureTable
2. Power block test results. An assessment of the MVC performance was conducted about two years after the system was
commissioned. The performance improvement of the plant on AGC control was remarkable. Source: GE Power
Dispatch ramp
(MW)
500-525
252-550
MVC
status
Off
On
Off
On
500-525
252-550
Off
On
Off
On
Average AGC
demand (MW)
518.4
512.4
530.5
532.8
511.5
545.3
520.8
531.8
Note: AGC = automatic generation controls.
June 2011 | POWER
www.powermag.com
41
Average actual
production (MW)
533.2
522.9
537.9
527.4
527.5
523.5
531.8
527.3
Standard
deviation (MW)
Power Block 1
7.2
4.7
7.2
5.0
Power Block 2
7.8
5.0
10.9
5.1
Improvement
in standard
deviation (%)
35
31
Difference between AGC
demand and AGC average
actual (MW)
-14.8
-10.5
-7.4
5.4
36
53
-16
-8.2
-11
4.5
Improvement in
AGC control (%)
29
27
49
59

http://www.powermag.com

POWER June 2011

Table of Contents for the Digital Edition of POWER June 2011