Training on power plant control loops

1. 2nd UCTE project
Training
Phase 1
Item 2
Power Plant Unit Control Structures
and Operating Modes related to
Frequency Control Issues
Oguz YILMAZ
Tubitak-UZAY
oguz.yilmaz@uzay.tubitak.gov.tr

2. • Gas Turbine and Comined Cycle Power Plants
• Operating Modes
• Variable maximum power, ambient conditions
dependency
• Requirement for continuous reserve control
• Example simulations with dynamic models
• Hydro Power Plants
• Operating Modes
• Example simulations with dynamic models
• Lignite/Coal Fired Thermal Units (steam turbines)
• Operating Modes
• Example simulations with dynamic models
• Operational directives to power plants
SUMMARY

3. 8 Unit Control Structures and Operating Modes
Combined Cycle Power Plants
•Constant Load Control (MW Setpoint Control)
(Plant or Gas Turbine)
•Maintain constant MW setpoint whatever the frequency is
•Transient or no response to frequency deviations
•Unpreferred operating mode for system requirements related to primary
frequency control
•Primary Control (Droop Mode, Governor Free Operation)
•Dynamic response to frequency deviations
•Requirement for Reserve (Very Important !!!)
•Base Load (Temperature Control)
•Best operating mode for efficiency. BUT !!!
•Worst operating mode for frequency control!!!!!!!!
•Secondary Control
•Remote determination of Steady State operating point of a Power Block (1/2
GT + ST)
•Primary Control ACTIVE !!!
•Plant Load Controller Details are very very important

4. Gas Turbine
Combustor
Compressor
&
IGVs
Turbine
P2
T1 T2,
P1
Air, P1=Patm
Exhaust
Flow to
HRSG
Fuel
•Why maximum power is dependent on ambient conditions
and even frequency ???
oguz.yilmaz@uzay.tubitak.gov.tr

5. Governor
Temp.
Control
M
i
n
S
e
l
e
c
t
Gas
Control
Valve
Turbine
Frequency
Droop
Speed/Load
Reference
(Raise/Lower)
Power
Gas turbine principal control block diagram
Dead
Band
oguz.yilmaz@uzay.tubitak.gov.tr

6. Reserve Control
Governor
Temp
Control
M
i
n
S
e
l
e
c
t
Gaz
Kontrl
Vanası
Turbin
Frequency
Droop
Speed/Load
Reference
(Raise/Lower)
Power
t(24 saat)
6:00 15:00 24:00
6:00
Max power (observation,
calculation, correction)
Steady state operating
point at 50 Hz
•For the short term state of the compressor, temperature dependency of
maximum power can be foreseen.
•For the long term state of the compresor observation is necessary
% Power
reserve
100
97.5
98
95.5
Continuous control for %2.5 reserve
IGV< IGV max should be satisfied (Reserve Air !!!)
oguz.yilmaz@uzay.tubitak.gov.tr

7. %P
f(Hz)
50
Speed Droop
% ∆f / %∆P @ steady state
200 mHz= 0.2/50 x100 =%0.4
If Droop=%5
%∆P= %∆f / %droop x100
%∆P=0.4 / 5 x100 =%8
Then,
200 mHz => %8 (if reserve exists !)
100 mHz => %4 (if reserve exists !)
50 mHz => %2 (if reserve exists !)
90 95 97.5 100
Temperature
Control
Limit
oguz.yilmaz@uzay.tubitak.gov.tr

8. •Same reserve
•Different droop

9. 9
Example Simulations
Scenario 1
Combined Cycle=0.90;0.95 Gas Turbini=0.90;0.95
Dynamic response to +/- 200 mHz frequency deviation
Plant Load Controller details (limiters)
oguz.yilmaz@uzay.tubitak.gov.tr

10. 8 Unit Control Structures and Operating Modes
Hydro Units
•Constant Wicket Gate Opening Control
(Opening Limiters) (Constant Load Control)
•Constant output power whatever the frequency is
•No primary response to frequency deviations.
•Primary Control (Droop Mode, Governor Free
Operation)
•Dynamic responses to frequency deviations
•Requirement for reserve
•Governor settings are important !!! (island mode stability)
•Secondary Control
•Primary Control Active (Governor free, active)
•Steady state operating point is remotely
determined.
oguz.yilmaz@uzay.tubitak.gov.tr

11. 8 Unit Control Structures and Operating Modes
Hydro Units –Speed Regulator Block Diagram
oguz.yilmaz@uzay.tubitak.gov.tr

12. 12
Example Simulations
Scenario 2
Hydro=0.90; 0.95
Dynamic Response to +/- 200 mHz frequency deviations
Opening Limiter
Island Mode Stability
oguz.yilmaz@uzay.tubitak.gov.tr

13. 8 Unit Control Structures and Operating Modes
Lignite/Coal Fired Units (steamers)
•Pressure Control
•Turbine => Pressure Control
•Boiler => Load Controlu (or manual under operator control)
•No or transient response to frequency deviations.
•Change of output depending on caol input quality
•Constant Load Control (constant MW setpoint control,
Load Limit Control)
•Turbine => MW setpoint control
•Boiler => Pressure Regulation (Eğer otomasyon yeterli ise)
•No or transient response to frequency deviations.
•Primary Control (Droop Mode, Governor Free Operation)
•Turbine => Speed Control /Frequency influenced power control
Dynamic response to frequency deviations
•Boiler => Pressure Control (if automation is enough)
•Boiler Following the Turbine and catches up with the pressure
•Coordinated Control
•Secondary Control
•Primary Control Active (Governor free, active)
•Steady state operating point is remotely determined.

14. 8

15. 22/09/09D4121/TRA/2009-00512-1-A15
Example Simulations
Scenario 3
CoalFired=0.90; 0.95
Dynamic response to +/- 200 mHz frequency deviations
Successful/Unsuccessful Pressure Regulation
Load Controller Details (Limiters)
oguz.yilmaz@uzay.tubitak.gov.tr

16. 8 Directives to the Power Plants
•Requirement to set up a common language
•System Details =>meaningful for system operators (TSOs)
•Power Plant details =>meaningful for plant operators
•Common language for common operating modes
•Constant load control, primary control, remote control via AGC
with active primary control etc...
•Requirement to have the fundamental information
related to generating units.
•For generating units,
•speed droop or MW/Hz (or MW/0.2 Hz),
•minimum reserve amount,
•whether limiters are applied or not (primary reserve changes
with operating point unless limiters are applied)
•Maximum and minimum values for secondary control range
Should be known and validated by after incident records.
•Contactual details related to Private generation companies must be
very well known.
oguz.yilmaz@uzay.tubitak.gov.tr