Demonstration of PSAPAC:
A Case Study on Its Application to
Three-Gorges Power System
Zheng Yan
Center for Electrical Energy Systems
The University of Hong Kong
Why this Demonstration
 Technical evaluations will be indispensable
in investigating feasibility and performance
of Northeast Asia power grid
interconnection
 Certain similarities between Northeast Asia
power grid interconnection and Three
Gorges project in China
Contents
 Background
 Procedures of investigating Three Gorges
Power System by PSAPAC
 Some specific results (comparison with
BPA program)
 A preliminary view of running PSAPAC
Background
1. PSAPAC of EPRI, USA
 The Power System Analysis PACkage,
developed by Powertech Labs Inc., for the
Electric Power Research Institute, USA,
is a comprehensive suit of advanced
computer programs for investigating power
systems.
Background
 Major Programs included in PSAPAC
» IPFLOW (Interactive Power FLOW Program)
» ETMSP (Extended Transient/Midterm Stability
Program)
» SSSP (Small Signal Stability Package)
» VSTAB (Voltage STABility Analysis Program)
» DIRECT 4.0 (A BCU based Direct Stability
Analysis Program distributed in companion
with PSAPAC)
Background
 PSAPAC has great capability to perform
power system analysis and has been widely
used in America, Canada, and many other
countries and districts.
 PSAPAC was mainly designed and
developed for North American systems.
Background
2. Asian Power Systems
 The Asian power system market is the
fastest growing market in the world.
 The Asian power systems have many
different technical aspects from North
American power systems.
 Application of PSAPAC to Asian systems
needs investigation.
Background
3. EPRI Contract with HKU
 In order to introduce PSAPAC to Asia, an
EPRI project contract WO4557-02 has been
signed by EPRI with CEES (Center for
Electrical Energy Systems of the University
of HK) to conduct the feasibility study.
 PSAPAC installed in workstations of CEES
at HKU for this project.
Background
 Applying PSAPAC to East-China power
system and the Three Gorges power system
had been conducted in co-operation with
Chinese EPRI. And results are comparable
with PSS/E and BPA programs.
 Some results on Three Gorges Power
System will be reported in this
demonstration.
Three Gorges Power System
Three Gorges Power
System consists of:
1. East China Power System:
Shanghai, Jiangsu, Zhejiang,
Anhui
2. Central China Power
System:
Hubei, Hunan, Jiangxi, Henan
3. Sichuan Power System
Three Gorges Power system
Three Gorges Hydro Power Station




Three Gorges Project on the Yangtze River bagan
to be built on Oct. 14, 1994.
The dam of the Three Gorges Project is located in
Yichang county of Hubei province, 40 km north of
Gezhouba dam.
Dam height: 185m; Normal water level: 175m.
In Three Gorges Hydro Station (TGHS), there will
be total 26 units of generators.
Three Gorges Power system





By the year 2003, the first generator unit will be
put into operation.
By 2010, all the 26 units would be ready to
generate electricity.
The rated capacity of a single unit is 700MW and
the total capacity of the station is 18200MW.
Electricity production: 84.7TWh per year.
Three Gorges Project is the biggest water
conservancy project in the world.
Three Gorges Power system
 Major transmission Projects in Three gorges
power system
1. From Three Gorges Hydro Station to East
China power system:
» Transmission distance: 1000 km
» Normal transmission power: 7200 MW
» HVDC Transmission line: 500kV
Three Gorges Power system
2. From Three Gorges Hydro Station to
Central China power system:
» Transmission distance: 600 km
» Normal transmission power: 2000 MW
» AC Transmission lines: 500kV
Programs of PSAPAC-IPFLOW
 IPFLOW
Interactive Power Flow Program for
solving power flow equations.
f (u , x )  0
g (u , x )  0
For power equilibrium
For static security
u is vector of control variables (generator
voltages and real power generations).
x is vector of state variables (load voltages).
Programs of PSAPAC-IPFLOW
 Algorithms
»
»
»
»
»
Newton method
BX version fast decoupled power flow
XB version fast decoupled power flow
Automatic solution
DC power flow
Programs of PSAPAC-ETMSP
 ETMSP
Extended transient/midterm stability
program studies the stability of the
system after a large disturbance.
Solving two sets of differentialalgebraic equations.
Programs of PSAPAC-ETMSP
 DAE systems to be solved
 du
(f )

f
(u , x )

 dt
 0  g ( f ) (u , x )

For fault-on system
 du
( p)

f
(u , x )

 dt
 0  g ( p ) (u , x )

For post-fault system
Programs of PSAPAC-ETMSP
 Major Algorithms
» Fourth order Runge-Kutta method
» Fourth order Gill-Runge-Kutta method
» Implicit trapezoidal method
Programs of PSAPAC-ETMSP
An example of unstable case
m a c hine a ng le s
1200
1000
angle in degrees
800
600
400
200
0
-2 0 0
0
2
4
6
s e c o nd s
8
10
Programs of PSAPAC-ETMSP
An example of stable case
m a c hi ne a ng le s
90
80
angle in degrees
70
60
50
40
30
20
10
0
0
2
4
6
s e c o nd s
8
10
Programs of PSAPAC-SSSP
 SSSP
Small signal stability program studies the
system’s stability in the equilibrium point.
Programs of PSAPAC-SSSP
 Form linearized DAE system around current
equilibrium point
 d u
 A u  B  x

 dt
0  C u  D x


d u
 A u
dt
A  ( A  BD
 Compute the eigenvalues of matrix
A
1
C)
Programs of PSAPAC-SSSP
 Major algorithms
» MASS (Multi-Area Small Signal Stability
Program): Computing all eigenvalues by QR
decomposition algorithm.
» PEALS (Program for Eigenvalue Analysis of
Large Systems): Computing some or more
selected eigenvalues by MAM and AESOPS
methods.
Programs of PSAPAC-VSTAB
 VSTAB
» Capability to automatically determine, from a
given operating condition, the nearest point of
instability, or maximum loading point.
Programs of PSAPAC-VSTAB
Typical P-V Curve
Voltage (p.u.)
1.20E+00
1.00E+00
8.00E-01
6.00E-01
4.00E-01
2.00E-01
0.00E+00
0
0.5
1
1.5
Lambda (Transfer Power)
2
2.5
Programs of PSAPAC-VSTAB
 Algorithm
» Continuation power flow
DIRECT4.0
 DIRECT4.0 - Direct method for transient
stability assessment
» To calculate the controlling UEP relevant to a
given fault for stability assessment.
 Program developed by Empros for EPRI
» Fast: Avoiding time-consuming integration
» Energy margin: An index to reflect the degree
of stability or instability.
DIRECT4.0
 BCU method (Invented by Felix F. Wu,
H.D. Chiang, P.Varaiya)
» A Boundary-Based Controlling Unstable
Equilibrium Point method
» Calculating the Controlling UEP through a
reduced-state gradient system
» BCU method is currently the only method used
in DIRECT4.0
Procedures of Investigation
 Data collection
 System reduction
 Creation of User Defined Controls for
devices which are not included in PSAPAC
 Study of cases with major concerns
 Comparison of results with other programs
 Suggestions
Data collection and system
reduction
1. Data collection and system reduction




Central China power system: Hubei, Henan,
Hunan and Jiangxi provincial power systems
East China power system: Anhui, Jiangsu,
Shanghai and Zhejiang provincial power systems
Sichuan power system
The purpose of network reduction is to focus on
the most interested components of the system.
Data collection and system
reduction
2. The Simplified Network (Year 2005 peak)

Total 21 equivalent generators in TGPS. Among
these generators, 12 generators locate in Central
China and Sichuan System, 9 in East China.




71 AC buses.
57 500kV transmission lines.
36 transformers.
2 HVDC transmission lines.
Data collection and system
reduction
East China
Number of Generators: 9
Number of Bus: 30
No. of Zones: 4 (Shanghai, Jiangsu,
Anhui, Zhejiang)
HVDC converters locate at the Shanghai
and Anhui zones (SSZD and NAQD)
Data collection and system
reduction
Data collection and system
reduction
 Central China
–Number of Generators: 12
–Number of Bus: 41
–No. of Zones: 5 (Hubei, Hunan, Jiangxi,
Sichuan, Henan)
–HVDC converters locate both at the
Hubei zone (SAZD and GZBD)
Data collection and system
reduction
Three Gorges Power system
Z o ne a nd area na m e s o f T G P S
N o.
1
2
3
4
5
6
7
8
9
Z one nam e
EE
XX
GG
YY
SC
SH
JS
AH
ZJ
P rovince or C ity nam e
H ubei province
H unan province
Jiangxi province
H enan province
S ichuan province
S hanghai C ity
Jiangsu province
A nhui province
Z hejiang province
10
DD
H V D C lines
A rea nam e
C entral C hina
C entral C hina
C entral C hina
C entral C hina
S ichuan sys.
E ast C hina
E ast C hina
E ast C hina
E ast C hina
B etw een C entral
and E ast C hina
C hina
User Defined Controls
3. User Defined Controls
 For implementing advanced power system
components, HVDC converters and controls,
so that PSAPAC can handle models not
included in the program
Individual Phase Control (IPF) HVDC model
IPFLOW Results
P ow er flow S u m m ary
IP F L O W
BPA
A ctiv e P o w er
(M W )
R ea ctiv e P o w er
(M V A R )
A ctiv e P o w er
(M W )
R ea ctiv e P o w er
(M V A R )
G en era tio n
9 7 2 3 3 .8
4 3 3 4 0 .9
9 7 2 3 4 .4
4 3 3 5 0 .7
Load
1 9 1 2 5 .3
1 2 4 9 0 .3
1 9 1 2 5 .3
1 2 4 9 0 .3
8 5 8 .5
1 8 2 1 7 .2
8 6 0 .7
1 8 2 2 6 .7
0 .0
1 1 1 6 3 .7
0 .0
1 1 1 6 3 .6
7 7 2 5 0 .0
2 3 7 9 7 .0
7 7 2 4 8 .4
2 3 7 9 7 .3
L in e an d
T ran sform er L osses
L in e C h a rg e
B u s S h u n t A d m itta n ce
IPFLOW Results
IP F L O W
BPA
Load
G en era tio n
Shunt
(M v a r )
(M W )
(M W )
(M W )
(M v a r
)
0 .0
0 .0
7 9 6 0 .0
7 5 3 5 .7
0 .0
0 .0
0 .0
0 .0
0 .0
0 .0
0 .0
0 .0
0 .0
1 8 1 5 9 .0
4 5 3 1 .0
6 2 4 5 .3
3 4 5 3 .6
1 8 1 5 9 .0
4 5 3 1 .4
6 2 4 5 .3
3 4 5 3 .6
3 9 4 0 .0
5 2 3 9 .0
0 .0
0 .0
3 9 4 0 .0
5 2 3 9 .4
0 .0
0 .0
JS
1 3 9 5 5 7 .3
1 5 4 9 9 .0
0 .0
0 .0
1 3 9 5 6 .9
1 5 4 9 9 .0
0 .0
0 .0
SC
1 4 0 2 6 .0
6 4 3 5 .0
7 6 0 6 .0
4 2 7 1 .7
1 4 0 2 6 .0
6 4 3 5 .6
7 6 0 6 .0
4 2 7 1 .7
SH
9 6 2 8 .0
1 1 6 9 0 .0
0 .0
0 .0
9 6 2 8 .0
1 1 6 8 8 .6
0 .0
0 .0
XX
7 2 1 7 .8
8 2 4 5 .0
0 .0
0 .0
7 2 1 8 .5
8 2 4 4 .6
0 .0
0 .0
YY
9 8 4 5 .0
6 5 2 4 .0
5 2 7 4 .0
4 7 6 5 .0
9 8 4 5 .0
6 5 2 3 .5
5 2 7 4 .0
4 7 6 5 .0
ZJ
1 2 5 0 1 .0
1 1 5 5 0 .0
0 .0
0 .0
1 2 5 0 1 .0
1 1 5 5 0 .6
0 .0
0 .0
G en era tio n
Shunt
(M W )
(M W )
(M W )
AH
7 9 6 0 .0
7 5 3 6 .0
DC
0 .0
EE
GG
Load
Zone
ETMSP Results
BPA Results
ETMSP Results
ETMSP Results
BPA Results
ETMSP Results
Some Comments
 IPFLOW and BPA power flow program
have the same calculation results in
engineering accuracy.
 ETMSP and BPA transient stability program
also have comparable computation results in
engineering accuracy.
Some Comments
 ETMSP has strong modeling capability and
is also convenient to perform hybrid AC/DC
power system transient simulations.
 The UDC part of the HVDC model are very
flexible.
 PSAPAC can be applied to Chinese power
systems.
Some Suggestions
PSAPAC Requires Improvements in the
following aspects:
 User-friendly interface;
 Unified database management;
 Graphic output;
 Network diagram display.
Some Suggestions
 We found that the time step of ETMSP should
be at least 10 times smaller than BPA in order
to get the same precision in the case of hybrid
ac/dc system. Enhancement of HVDC model
and improvement of integration algorithms can
be carried on.
 The command line user interface is
inconvenient to use. Windows-based
interface should be developed.
Demonstration
Demonstration
 Case 1: fd4hd1 / fault in East China system
 Case 2: fd4hd2 / fault in East China system
 Case 3: fd4hz1 / fault in Central China system
 Case 4: fd4hz2 / fault in Central China system
 Case 5: fd4hz3 / fault in Central China system
 Case 6: Direct4.0 stable case for 161-machine

system
Case 7: Direct4.0 unstable case for 163machine system
Final Conclusions
 Technical issues arising from interconnection
of Northeast Asia power grids are very
complex, and definitely more complicated
than the Three Gorges power system.
 Suitable software tools are playing extremely
important roles in studying the Northeast
Asian power grid, and be helpful to
understanding the characteristics of the
system.
Final Conclusions
 We believe that, at different stages of the
system development, different software
tools with different degrees of complexities
and capabilities can be used for
investigation.
 This presentation is just a Case Study, it
does not have any intention to proposing
PSAPAC as the only tool.