© ABB Group May 3, 2023 | Slide 1
Improving Power System Stability Through Integrated Power System Stabilizers
Rudolf Wieser, Matthias Baechle, Valerijs Knazkins – ATPE
© ABB Group May 3, 2023 | Slide 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 May 3, 2023 | Slide 3
The main functions of an AVRAutomatic 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 May 3, 2023 | Slide 4
Model of a single Generator connected to GridTurbine and Generator Mechanics
Turbine driving torque Tm Generator braking torque Te Mechanical rotational speed ω
GeneratorTurbineω
Tm
Te
© ABB Group May 3, 2023 | Slide 5
Model of a single Generator connected to GridTurbine and Generator Connection to Grid
Turbine + Generator Generator breaker Step-up transformer Transmission line Infinite bus (constant voltage)
GeneratorTurbine
© ABB Group May 3, 2023 | Slide 6
Model of a single Generator connected to GridTurbine and Generator connected to Grid
GeneratorTurbine
A single generator connected to a large grid can be represented by the Phillips-Heffron model (assuming constant field voltage and mechanical torque)
K3s K3 T’do + 1
K2 K2K6 K5
K2
K4
K2
12H s
K2K1
2pi*fNs∆Tm
∆Te
∆δ
∆Vg
∆E’q
∆ω
© ABB Group May 3, 2023 | Slide 7
Model of a single Generator connected to GridLinearized 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)
K3s K3 T’do + 1
K2 K2K6 K5
K2
K4
K2
12H s
K2K1
2pi*fNs∆Tm
∆Te
∆δ
∆Vg
∆E’q
∆ω
© ABB Group May 3, 2023 | Slide 8
Model of a single Generator connected to GridTorque Disturbance Impact
Harmonic Phasor Representation Torque equilibrium disturbance Electric torque produces natural positive damping
K3s K3 T’do + 1
K2 K2K6 K5
K2
K4
K2
12H s
K2K1
2pi*fNs∆Tm
∆Te
∆δ
∆Vg
∆E’q
∆ω
0°
© ABB Group May 3, 2023 | Slide 9
Model of a single Generator connected to GridFast Voltage Control Impact
Harmonic Phasor Representation Generator plus AVR Electric torque form AVR function produces
negative damping torque
K3s K3 T’do + 1
K2 K2K6 K5
K2
K4
K2
12H s
K2K1
2pi*fNs
Kas Ka + 1
∆Tm
∆Te
∆δ
∆Vg
∆E’q
∆Vfd
∆ω
© ABB Group May 3, 2023 | Slide 10
Model of a single Generator connected to GridPower System Stabilizer Function
Power System Stabilizer (PSS) Band limited damping torque contribution Speed estimator from electrical voltage and current signals
K3s K3 T’do + 1
K2 K2K6 K5
K2
K4
K2
12H s
K2K1
2pi*fNs
Kas Ka + 1 PSS
∆Tm
∆Te
∆δ∆ω
∆Vg
∆E’q
∆Vfd
∆Vgref
© ABB Group May 3, 2023 | Slide 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 May 3, 2023 | Slide 12
Synchronous Machine Transient Simulator Turbine, Generator, Transformer, Line to infinite Bus
Typical turbine - generator arrangement in a power plant Automatic Voltage Regulator (AVR)
GeneratorTurbine
AVRExcitation
Governor
© ABB Group May 3, 2023 | Slide 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
GeneratorTurbine
AVRExcitation
Governor
© ABB Group May 3, 2023 | Slide 14
Synchronous Machine Transient Simulator Turbine, Generator, Transformer, Line to infinite Grid
SMTS-RT
GeneratorTurbine
AVRExcitation
Governor
AVR hardware in the loop Real Time Simulation
© ABB Group May 3, 2023 | Slide 15
Synchronous Machine Transient Simulator Turbine, Generator, Transformer, Line to infinite Grid
SMTS-RT 6000
UNITROL 6000
© ABB Group May 3, 2023 | Slide 16
Synchronous Machine Transient Simulator SMTS-RT 6000; User Interface
© ABB Group May 3, 2023 | Slide 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 May 3, 2023 | Slide 18
AVR Grid Code ComplianceGrid 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 May 3, 2023 | Slide 19
Grid Code Compliance Testing
Test scheme for the measurement of the corresponding transfer function
K3s K3 T’do + 1
K2 K2K6 K5
K2
K4
K2
12H s
K2K1
2pi*fNs
Kas Ka + 1 PSS
∆Tm
∆Te
∆δ∆ω
∆Vg
∆E’q
∆Vfd
∆Vgref ∆Vgref = Vinjection
White noise
∆Te , ∆Pe
© ABB Group May 3, 2023 | Slide 20
Grid Code Compliance Testing
Time domain-response of the system without the stabilizer, while injecting noise signals:
ExpertDays09
© ABB Group May 3, 2023 | Slide 21
Grid Code Compliance Testing
Time domain-response of the system with the stabilizer, while injecting noise signals:
8%
ExpertDays09
© ABB Group May 3, 2023 | Slide 22
Grid Code Compliance Testing
Time domain-response of the system with the stabilizer, while injecting noise signals:
ExpertDays09
© ABB Group May 3, 2023 | Slide 23
Grid Code Compliance Testing
Frequency domain response of the system with (green line) and without (blue line) the stabilizer connected:
( )( )( )
e
ref
P jF jV j
-20
-15
-10
-5
0
5
10
15
20
25
Mag
nitu
de [d
B]
Frequency [Hz]
10.2 5
© ABB Group May 3, 2023 | Slide 24
Grid Code Compliance Testing
Time domain response of the system with (using different gains) and without (blue line) the stabilizer connected:
time [s]0 2 4 6 8
0.83
0.84
0.85
0.86
0.87P
e [p
.u.]
w/o PSS
with PSS, KS1=2
with PSS, KS1=3
with PSS, KS1=4
with PSS, KS1=10
© ABB Group May 3, 2023 | Slide 25