Parameter Sensitivity Analysis for Sub-Synchronous

LOGO
Parameter Sensitivity Analysis for
Sub-Synchronous Oscillations in
Wind-Integrated Power Systems
Meng Wu1, Rongfu Sun2, Lin Cheng3, and Le Xie1
1: Texas A&M University, 2: China Jibei Power Grid, 3: Tsinghua University
10-21-2014
Wind Farm SSO Events in Real World
Wind Farm SSO in Real World
 In Oct. 2009, ERCOT reported a SSO in wind-integrated system, triggered
by a single line-to-ground fault.
 A NREL report in 2013 presents several SSO incidents recorded by wind
power plants of Oklahoma Gas & Electric Company.
 China Jibei Power Grid also encounters SSO induced by wind power
integration.
2
Y. H. Wan, “Synchronized phasor data for analyzing wind power plant dynamic behavior and model validation”, 2013.
P. Belkin, “Event of 10-22-09”, in CREZ Technical Conference, 2010.
Basic Characteristics of Wind Farm SSO
Characteristics of Wind Farm SSO
 Electrical oscillation typically in the frequency range of
20 – 50 Hz.
 Caused by interactions among wind generators,
controllers of power electronic devices, and series
compensated network.
 Can be difficult to filter since the oscillation frequency
may be close to synchronous frequency.
 DFIG-based wind turbine are most sensitive to SSO
among all kinds of wind turbines.
3
Garth Irwin, “Sub-synchronous control interaction studies related to the CREZ project”, 2010
How to Deal With Wind Farm SSO?
Wind Farm SSO
Phenomenon
Wind Farm SSO
Can Be
Eliminated Effectively
4
Identify Root Cause
Identify Critical
Parameters& Inputs
• Small-signal
instability induced
by certain parameter
settings and input
conditions
• Eigenvalue
sensitivities with
respect to system
parameters & input
conditions
Verification
Through Simulation
Sensitivity-Based
Mitigation Control
• Sensitivity-based
optimal parameter
adjustment for wind
farm SSO mitigation
Wind Farm SSO vs Parameters & Inputs
System Nonlinear Model
Small-Signal Stability
Study eigenvalues of A matrix:
 negative real part -> stable
 positive real part -> unstable
System Linearized Model
A matrix of the linearized system
can be expressed as
function of ONLY
system parameters & inputs
Wind SSO Stability
Linearized State Matrix
Small Signal stability of Wind Farm SSO
is determined by ONLY
system parameters & inputs
5
How to Deal With Wind Farm SSO?
Wind Farm SSO
Phenomenon
Wind Farm SSO
Can Be
Eliminated Effectively
6
Identify Root Cause
Identify Critical
Parameters& Inputs
• Small-signal
instability induced
by certain parameter
settings and input
conditions
• Eigenvalue
sensitivities with
respect to system
parameters & input
conditions
Verification
Through Simulation
Sensitivity-Based
Mitigation Control
• Sensitivity-based
optimal parameter
adjustment for wind
farm SSO mitigation
Eigenvalue Analysis – Low Wind Speed
System Condition
 Steady-State Infinite Bus |V| = 1 pu
 Steady-State Infinite Bus θ = 0 rad
 Steady-State DFIG Pout = 1 pu
 Steady-State DFIG Power Factor = 0.9
 Wind Speed = 4 m/s
 Series Compensation Level = 52.38%
 5 oscillation modes in total: 3 sub-synchronous and 2 super-synchronous
 22.06 Hz sub-synchronous mode is unstable in low wind speed condition.
 The other two sub-synchronous modes are stable with small damping compared with supersynchronous modes.
7
Sensitivity Analysis for SSO Modes
Eigenvalue Sensitivities for 22.06 Hz Mode
0.1
0.5
0
0
-0.5
-0.1
D
K
Jw Jg Xls Xm Xlr Rs Rr Rnt Lnt Cnt Xxf Kte T te Kiqr T iqr Kqs T qs Kidr T idr Kqg T qg KiqgT iqg Kdc T dc KidgT idg Cdc
System Parameters
Eigenvalue Sensitivities for 8.09 Hz Mode
0.1
-1
Wr Pe Qe Eq Ed Vdc
Operating Conditions
0.3
0.2
0.1
0
0
-0.1
D
K
Jw Jg Xls Xm Xlr Rs Rr Rnt Lnt Cnt Xxf Kte T te Kiqr T iqr Kqs T qs Kidr T idr Kqg T qg KiqgT iqg Kdc T dc KidgT idg Cdc
System Parameters
Eigenvalue Sensitivities for 1.27 Hz Mode
0.01
-0.1
4
Wr Pe Qe Eq Ed Vdc
Operating Conditions
x 10
-3
2
0
0
-0.01
-2
D
K
Jw Jg Xls Xm Xlr Rs Rr Rnt Lnt Cnt Xxf Kte T te Kiqr T iqr Kqs T qs Kidr T idr Kqg T qg KiqgT iqg Kdc T dc KidgT idg Cdc
System Parameters
Torsional
System
8
DFIG
System
Network
System
Controller
System
-4
Wr Pe Qe Eq Ed Vdc
Operating Conditions
Operating
Conditions
Sensitivity Analysis for SSO Modes
 22.06 Hz mode is sensitive to network parameters and DFIG converter controller parameters.
 8.09 Hz mode is sensitive to DFIG parameters and network parameters.
 1.27 Hz mode is sensitive to torsional system parameters, network parameters and controller parameters.
 Network inductor and capacitor values are of high sensitivities in all three sub-synchronous modes.
 Parameters in current control loops of converter controllers have higher sensitivities over torque control loops.
 DFIG rotor speed (determined by wind speed) has significant influence on all three modes.
450
400
DFIG Rotor Speed (rad/s)
350
300
250
200
150
100
DFIG Rotor Speed at Different Wind Speed
System Synchronous Speed
50
0
0
5
9
10
15
Wind Speed (m/s)
20
25
30
How to Deal With Wind Farm SSO?
Wind Farm SSO
Phenomenon
Wind Farm SSO
Can Be
Eliminated Effectively
10
Identify Root Cause
Identify Critical
Parameters& Inputs
• Small-signal
instability induced
by certain parameter
settings and input
conditions
• Eigenvalue
sensitivities with
respect to system
parameters & input
conditions
Verification
Through Simulation
Sensitivity-Based
Mitigation Control
• Sensitivity-based
optimal parameter
adjustment for wind
farm SSO mitigation
Simulation Results Before Parameter Adjustment
T ransmission Line Current (pu)
FFT Analysis of Line Current
0.3
0.12
0.2
0.1
0.1
0.08
0
0.06
-0.1
0.04
-0.2
0.02
1
0
2
3
0
0
4
 Oscillation frequency
of transmission line
current: 27.92 Hz
20
T ime (s)
40
80
60
100
Frequency (Hz)
DFIG Electrical T orque (pu)
 Oscillation frequency
of DFIG electrical
torque: 22.13 Hz
0.1
0
0.08
-0.1
0.06
-0.2
0.04
-0.3
0.02
-0.4
0
1
2
T ime (s)
11
FFT Analysis of DFIG Electrical T orque
0.1
3
4
0
0
10
20
30
Frequency (Hz)
40
50
Simulation Results Before Parameter Adjustment
T ransmission Line Current (pu)
FFT Analysis of Line Current
0.2
0.12
-
0.1
0.1
0.08
0
0.06
-
0.04
-0.1
-
 Gain of GSC current
control loop (Kiqg) is
tuned for SSO mitigation
from 1.0 to 0.5
0.02
-0.2
0
1
2
3
4
0
0
20
T ime (s)
40
60
80
Frequency (Hz)
FFT Analysis of DFIG Electrical T orque (p
DFIG Electrical T orque (pu)
0.1
-0.132
 Sensitive gains of
converter controller
are adjusted.
 Unstable eigenvalues
are moved left
effectively.
0.08
-0.133
0.06
-0.134
0.04
-0.135
-0.136
0
0
12
100
0.02
1
2
3
4
0
0
10
20
30
Frequency (Hz)
40
50
Conclusions
Conclusions
 What Happened: Sub-synchronous oscillation happens in windintegrated power system.
 Why It Occurred: Inappropriate operating conditions, seriescompensated network parameters as well as DFIG converter controller
parameters .
 How To Eliminate: Eigenvalue adjustment based on sensitivity analysis
and parameter tuning (including DFIG converter controller gains and
network compensation level).
Future Work
 Extend sensitivity analysis to multi-machine systems.
 Design optimal mitigation control strategies for wind farm SSO.
13
References
References
[1] Y. H. Wan, “Synchronized phasor data for analyzing wind power plant dynamic behavior and model
validation”, National Renewable Energy Laboratory, CO, Tech. Rep. NREL/TP-5500-57342, Jan
2013.
[2] P. Belkin, “Event of 10-22-09”, in CREZ Technical Conference, Jan 2010.
[3] Z. Lubosny, Wind Turbine Operation in Electric Power Systems: Advanced Modeling. Berlin,
Germany: Springer-Verlag, 2003.
[4] P. C. Krause, O. Wasynczuk, and S. D. Sudhoff, Analysis of Electric Machinery. NY: IEEE Press,
1995.
[5] P. M. Anderson, B. L. Agrawal, and J. E. Van Ness, Subsynchronous Resonance in Power Systems.
NY: IEEE Press, 1990.
[6] M. Wu, R. Sun, L. Cheng, and L. Xie, “Parameter sensitivity analysis for sub-synchronous control
interactions in wind-integrated power systems”, submitted to CIGRE Grid of the Future
Symposium, 2014, Houston, TX, Oct 2014
14
LOGO

Download Report