1999 IEEE PES Summer Meeting
Retuning Stabilizers for the North-South Brazilian
Interconnection
N.Martins, A.A.Barbosa, J.C.R.Ferraz M.G. dos Santos, A.L.B.Bergamo, C.S.Yung
CEPEL, Rio de Janeiro, Brazil
Eletrobrás, Rio de Janeiro, Brazil
V.R. Oliveira, N.J.P. Macedo
Furnas, Rio de Janeiro, Brazil
Brazilian
-South Interconnection
Brazilian North
North-South
Interconnection
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
2
Brazilian
-South Interconnection
Brazilian North
North-South
Interconnection -- Detail
Detail
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SOUTHEAST
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H YDR OE LEC TR IC P LA NT
SUB STATION
LT 230 kV
LT 3 45 kV
LT 500 kV
500 kV AC TRANSMISSION REINFORCEMENT ALTERNATIVE
NORTH-SOUTH INTERCONNECTION
Retuning Stabilizers for the North-South Brazilian Interconnection
Eletrobrás
GRUPO COORDENADOR DE PLANEJAMENTO
DOS SISTEMAS ELÉTRICOS - GCPS
North-South Interconnection
1999 IEEE PES Summer Meeting
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Retuning
-South
Retuning Stabilizers
Stabilizers for
for the
the Brazilian
Brazilian North
North-South
Interconnection
Interconnection
• Carried out by the Eletrobrás/GCOI task force NSPRE/R
• TCSC damping controllers previously defined by Planning Division
• Various base cases and (N-1) contingency scenarios have been
considered
• Integral of accelerating power PSSs
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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System
System Data
Data
• North-South interconnection
– 1000 km long, 1300 MW transfer, 500 kV compact line, series
compensated
– 2 TCSC’s (6% compensation each)
– 2300 bus model, 120 generators, 4 SVC’s, 1 HVDC link
– North-South mode (0.17 - 0.25 Hz) may become low damped
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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Retuning
Retuning Procedure
Procedure
• The retuning procedure comprises eight steps:
– Step 1 – Eigenvalue and Step Disturbance Studies on Individual
Generator Units
– Step 2 – Study of Three Base Cases
– Step 3 – Coordinated Design of TCSCs and PSSs
– Step 4 – Robustness Assessment of the PSS and TCSC Designs for
Multiple Scenarios
– Step 5 – Benchmarking Small Signal and Transient Stability Results
– Step 6 – Transient Stability Simulations
– Step 7 – Stabilizer Commissioning, Retuning and Power Plant Tests
– Step 8 – Power System Oscillation Monitoring
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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Exciting
-South Mode
Exciting the
the North
North-South
Mode the
the Most
Most
• Simultaneous disturbances of opposite polarities applied to North and
South generators
• Monitor the magnitude of power transients in the North-South tie
B ode Dia gra m
40
λ = -0.034 ± j 1.079
30
20
∆PN-S TIE(s)/Σ ∆P
∆PN-S TIE(s)/ ∆P
i
MEC(s)
i
MEC
(s)
Ma gnitude
10
0
-10
-20
-30
∆
/ ∆P
P iT(s)
i
MEC
(s)
-40
-50
0
1
2
3
Retuning Stabilizers for the North-South Brazilian Interconnection
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5
6
7
8
9
1999 IEEE PES Summer Meeting
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Step
Step Responses
Responses
• Step responses of major system generators for scenario R (1000MW
N/NE -> S/SE) with existing PSSs and without TCSC stabilizer
S te p Re s pons e s
0.2
Te rm ina l MW De via tion (pu)
λ = -0.034 ± j 1.079
0.1
0
-0.1
0
5
10
15
20
25
Retuning Stabilizers for the North-South Brazilian Interconnection
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1999 IEEE PES Summer Meeting
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Mode
-Shape for
-South Inter
-Area Mode
Mode-Shape
for North
North-South
Inter-Area
Mode
• Mode-Shape for North-South inter-area mode (λ = -0.034 ± j 1.079)
South-Southeast
Itaipu 50 Hz
Retuning Stabilizers for the North-South Brazilian Interconnection
North-Northeast
1999 IEEE PES Summer Meeting
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Ranking
Ranking the
the Most
Most Effective
Effective PSS
PSS Locations
Locations Based
Based on
on Transfer
Transfer
Function
Function Residues
Residues
• The residue ranking list of transfer functions ∆ωi(λ)/∆Vrefi (λ),
i = 1, ..., Ng helps locating the most effective generators for installing
or retuning existing PSS for damping the inter-area mode
λ = -0.034 ± j 1.079
Xingó
Itaparica
Paulo Afonso IV
Sobradinho
Retuning Stabilizers for the North-South Brazilian Interconnection
Itaipu
1999 IEEE PES Summer Meeting
1
0
PSS
PSS Tuning
Tuning and
and Coordination
Coordination for
for Damping
Damping Several
Several Dominant
Dominant
Modes
Modes
• Dominant pole spectrum for ∆ω(s)/∆Vref(s) at Xingó power plant. The
complex vectors are the transfer function residues associated with the
various poles. The residue magnitudes were made larger than actual
for readability
Imag.
(rad/s)
9.0
7.5
Local Northeastern Modes
6.0
4.5
3.0
North-Northeast Mode
1.5
North-South Mode
0.0
-1.25
-0.75
-0.25
Real
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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1
PSS
PSS Tuning
Tuning and
and Coordination
Coordination for
for Damping
Damping Several
Several Dominant
Dominant
Modes
Modes
Bode Plot
The PSS phase
determined so that the
residues associated with the
Magnitude (dB)
characteristics are
100
50
0
-50
150
about 8 rad/s are advanced
100
by about 70° while the
residue associated with the
North-South mode at 1 rad/s
experiences no phase
change.
Phase (deg)
multimachine modes at
50
0
-3
10
10
-2
10
-1
10
0
10
1
10
2
10
3
Frequency (rad/sec)
2
 3s  1 + 0.12 s   1 + 0.25s 
PSS ( s ) = K pss 

 

 1 + 3s  1 + 0.012s   1 + 0.75s 
Three Lead-Lag Blocks
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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PSS
PSS Tuning
Tuning and
and Coordination
Coordination for
for Damping
Damping Several
Several Dominant
Dominant
Modes
Modes
• This PSS tuning causes the original residues shown in to be rotated
and amplified as indicated in the figure below
• Dominant pole spectrum and residues for the open-loop transfer
function PSS(s).∆ω(s)/∆Vref(s). These residues correspond to the firstorder estimate for the Root-Locus plot, as the PSS gain at Xingó power
plant is raised from zero to 20 pu/pu.
Imag.
(rad/s)
9.0
7.5
Local Northeastern Modes
6.0
South-Southeast Mode
4.5
3.0
North-Northeast Mode
North-South Mode
1.5
0.0
-1.25
-0.75
-0.25
Real
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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PSS
PSS Tuning
Tuning and
and Coordination
Coordination for
for Damping
Damping Several
Several Dominant
Dominant
Modes
Modes
• First-Order estimate of the Root-Contour plot as the gains of stabilizers
at Xingó, Paulo Afonso IV and Itaparica are raised from zero to 20
pu/pu
Imag.
(rad/s)
Local Northeastern Modes
9.0
7.5
6.0
South-Southeast Mode
4.5
North-Northeast Mode
3.0
1.5
North-South Mode
0.0
-2.50
-2.00
-1.50
-1.00
-0.50
0.00
Real
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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Examples
-Locus for
Examples of
of Root
Root-Locus
for Large
Large System
System Models
Models
• Root-Contour plot as the gains of the PSSs at Xingó, Paulo Afonso IV
and Itaparica are raised from zero to 25 pu/pu
imag
15%
10%
5%
Local Northeastern
Modes
South-Southeast
Mode
North-Northeast
Mode
North-South
Mode
real
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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Examples
-Locus for
Examples of
of Root
Root-Locus
for Large
Large System
System Models
Models
• Locus of North-South mode following changes in the PSS gains at
Xingó, Paulo Afonso IV and Itaparica power plants
imag
15%
10%
5%
KPSS = 0
Proposed PSSs
Existing PSSs
KPSS = 25
Existing
PSS Gains
real
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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Examples
Examples of
of Full
Full Eigensolution
Eigensolution for
for Large
Large Systems
Systems
• Eigenvalue spectrum of the North-South Brazilian interconnection with
existing PSSs and without TCSCs (1,700 state variables). The chosen
scenario is not critical
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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Examples
Examples of
of Full
Full Eigensolution
Eigensolution for
for Large
Large Systems
Systems
• Eigenvalue spectrum for the North-South Brazilian interconnection in
the absence of Power System Stabilizers and TCSC damping controllers
(1,300 State Variables)
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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Example
Example of
of Macro
Macro Functions
Functions Results
Results for
for Various
Various System
System
Scenarios
Scenarios
• Location of North-South Mode, considering 19 scenarios, with and
without stabilizers at Xingó, Paulo Afonso IV and Itaparica power plants
15%
10%
5%
Without Stabilizers
With Existing Stabilizers
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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Example
Example of
of Macro
Macro Functions
Functions Results
Results for
for Various
Various System
System
Scenarios
Scenarios
• Location of North-South Mode, considering 19 scenarios, with existing
and proposed stabilizers at Xingó, Paulo Afonso IV and Itaparica power
plants
15%
10%
5%
Existing Stabilizers
Proposed Stabilizers
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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0
Benchmarking
-Signal and
Benchmarking Small
Small-Signal
and Transient
Transient Stability
Stability Results
Results
• Comparison of small signal and transient stability program responses
for a small disturbance. System model with proposed PSSs in Paulo
Afonso IV and Xingó power plants (100 MVA base)
Active Power Flow Deviation - pu
North-South Tie-Line Power
0.1
Time (s)
0
-0.1
0
2
4
6
8
10
12
14
16
18
20
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
-0.8
-0.9
Transient Stability Software
Small Signal Stability Software
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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1
Example
Example of
of Transient
Transient Stability
Stability Simulation
Simulation
• Active power flow transients in the North-South intertie, after a fault
with subsequent line reclosure
1300
Power Flow (MW)
1200
1100
1000
900
800
Existing PSS's
700
Proposed PSS's in Xingó,
Paulo Afonso IV & Itaparica
600
0
5
10
Time (s)
15
Retuning Stabilizers for the North-South Brazilian Interconnection
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25
1999 IEEE PES Summer Meeting
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Conclusions
Conclusions
• Modified PSSs at 3 power plants plus the TCSCs provide an adequate
level of redundancy in the damping sources to the critical North-South
mode
• Advanced linear analysis software was instrumental to the success of
the damping analysis and control study
• Very low-frequency inter-area modes call for a tighter damping criteria
(ξ = 15%)
• GEP-based PSS tuning can be difficult sometimes
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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Example
Example of
of Macro
Macro Functions
Functions Results
Results for
for Various
Various System
System
Scenarios
Scenarios
• Location of three major inter-area modes for 64 N-1 contingencies in
the Argentinean interconnected system
Imag
15%
10%
5%
Real
Retuning Stabilizers for the North-South Brazilian Interconnection
1999 IEEE PES Summer Meeting
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GEP(s)
GEP(s) Phase
Phase Diagrams
Diagrams
140
Phase (degrees)
120
100
PVr
80
GEP(X’)
60
GEP(2X’)
40
GEP(no load)
GEP(R high,X high)
20
0
0
2
4
6
8
10
12
Retuning Stabilizers for the North-South Brazilian Interconnection
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18
20
1999 IEEE PES Summer Meeting
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Phase
Phase Diagrams
Diagrams for
for GEP(s)
GEP(s) and
and PSS(s)
PSS(s)
140
Phase (degrees)
120
100
80
60
PVr
40
PSS(ω max low)
PSS(ω max high)
20
0
GEP(R high,X high)
0
2
4
6
8
10
12
Retuning Stabilizers for the North-South Brazilian Interconnection
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18
20
1999 IEEE PES Summer Meeting
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