1. Rudolf Wieser, Matthias Baechle, Valerijs Knazkins – ATPE
Improving Power System Stability Through Integrated Power System Stabilizers
© ABB Group
April 16, 2017 | Slide 1

2. OUTLINE Controlled Generator on Grid
The main functions of an Automatic Voltage Regulator (AVR)
The main functions of a Power System Stabilizer (PSS)
How to test an AVR system
Introduction to Real time Simulator
Grid Code compliance testing
UNITROL built in compliance test functions
© ABB Group
April 16, 2017 | Slide 2

3. The main functions of an AVR Automatic Voltage Regulator
State-of-the-art excitation systems are equipped with fast acting voltage regulators:
Advantages:
Fast acting voltage control and reactive power support
Providing synchronizing torque component
Disadvantage:
Introducing negative damping torque component
Solution to the reduced damping torque problem
Power System Stabilizers
© ABB Group
April 16, 2017 | Slide 3

4. Model of a single Generator connected to Grid Turbine and Generator Mechanics
Turbine driving torque Tm
Generator braking torque Te
Mechanical rotational speed ω
© ABB Group
April 16, 2017 | Slide 4

5. Model of a single Generator connected to Grid Turbine and Generator Connection to Grid
Turbine + Generator
Generator breaker
Step-up transformer
Transmission line
Infinite bus (constant voltage)
© ABB Group
April 16, 2017 | Slide 5

6. Model of a single Generator connected to Grid Turbine and Generator connected to Grid
A single generator connected to a large grid can be represented by the Phillips-Heffron model (assuming constant field voltage and mechanical torque)
© ABB Group
April 16, 2017 | Slide 6

7. Model of a single Generator connected to Grid Linearized Model at certain Operating Point
A single generator connected to a large grid can be represented by the Phillips-Heffron model (assuming constant field voltage and mechanical torque)
© ABB Group
April 16, 2017 | Slide 7

8. Model of a single Generator connected to Grid Torque Disturbance Impact
Harmonic Phasor Representation
Torque equilibrium disturbance
Electric torque produces natural positive damping
© ABB Group
April 16, 2017 | Slide 8

9. Model of a single Generator connected to Grid Fast Voltage Control Impact
Harmonic Phasor Representation Generator plus AVR
Electric torque form AVR function produces negative damping torque
© ABB Group
April 16, 2017 | Slide 9

10. Model of a single Generator connected to Grid Power System Stabilizer Function
Power System Stabilizer (PSS)
Band limited damping torque contribution
Speed estimator from electrical voltage and current signals
© ABB Group
April 16, 2017 | Slide 10

11. OUTLINE Controlled Generator on Grid
The main functions of an Automatic Voltage Regulator (AVR)
The main functions of a Power System Stabilizer (PSS)
How to test an AVR system
Introduction to Real Time Simulator
Grid Code compliance testing
UNITROL built in compliance test functions
© ABB Group
April 16, 2017 | Slide 11

12. Synchronous Machine Transient Simulator Turbine, Generator, Transformer, Line to infinite Bus
Typical turbine - generator arrangement in a power plant
Automatic Voltage Regulator (AVR)
© ABB Group
April 16, 2017 | Slide 12

13. Synchronous Machine Transient Simulator Turbine, Generator, Transformer, Line to infinite Grid
SMTS-RT
Real Time Simulation of
Turbine and governor (simplified)
Generator
Breaker and step-up transformer
Grid representation with infinite Bus Voltage
© ABB Group
April 16, 2017 | Slide 13

14. Synchronous Machine Transient Simulator Turbine, Generator, Transformer, Line to infinite Grid
SMTS-RT
AVR hardware in the loop Real Time Simulation
© ABB Group
April 16, 2017 | Slide 14

15. Synchronous Machine Transient Simulator Turbine, Generator, Transformer, Line to infinite Grid
SMTS-RT 6000
UNITROL 6000
© ABB Group
April 16, 2017 | Slide 15

16. Synchronous Machine Transient Simulator SMTS-RT 6000; User Interface
© ABB Group
April 16, 2017 | Slide 16

17. OUTLINE Controlled Generator on Grid
The main functions of an Automatic Voltage Regulator (AVR)
The main functions of a Power System Stabilizer (PSS)
How to test an AVR system
Introduction to Real Time Simulator
Grid Code compliance testing
UNITROL built in compliance test functions
© ABB Group
April 16, 2017 | Slide 17

18. AVR Grid Code Compliance Grid Code Example
Excerpt from of a local grid code:
“Overall Excitation System Control Characteristic
…The frequency domain tuning of the Power System Stabilizer shall also be demonstrated by injecting a 0.2Hz-2Hz band limited random noise signal into the Automatic Voltage Regulator reference… while the Generating Unit is operating at a typical load level...
…The damping contribution of the Power System Stabilizer shall improve the system-stability within the frequency-band of interest (compared to the system response without a stabilizer):
i.e., 0.2Hz - 2Hz”
© ABB Group
April 16, 2017 | Slide 18

19. Grid Code Compliance Testing
Test scheme for the measurement of the corresponding transfer function
© ABB Group
April 16, 2017 | Slide 19

20. Grid Code Compliance Testing
Time domain-response of the system without the stabilizer, while injecting noise signals:
ExpertDays09
© ABB Group
April 16, 2017 | Slide 20

21. Grid Code Compliance Testing
Time domain-response of the system with the stabilizer, while injecting noise signals: 8%
ExpertDays09
© ABB Group
April 16, 2017 | Slide 21

22. Grid Code Compliance Testing
Time domain-response of the system with the stabilizer, while injecting noise signals:
ExpertDays09
© ABB Group
April 16, 2017 | Slide 22

23. Grid Code Compliance Testing
-20
-15
-10 -5 5 10 15 20 25
Magnitude [dB]
Frequency [Hz] 1
0.2
Frequency domain response of the system with (green line) and without (blue line) the stabilizer connected:
© ABB Group
April 16, 2017 | Slide 23

24. Grid Code Compliance Testing
Time domain response of the system with (using different gains) and without (blue line) the stabilizer connected:
time [s] 2 4 6 8
0.83
0.84
0.85
0.86
0.87
Pe [p.u.]
w/o PSS
with PSS, KS1=2
with PSS, KS1=3
with PSS, KS1=4
with PSS, KS1=10
© ABB Group
April 16, 2017 | Slide 24

25. © ABB Group
April 16, 2017 | Slide 25