demonstration of psapac: a case study on its application to three-gorges power system zheng yan...
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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.
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).
( , ) 0
( , ) 0
f u x
g u x
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 differential-algebraic equations.
Programs of PSAPAC-ETMSP
DAE systems to be solved
For fault-on system
For post-fault system
( )
( )
( , )
0 ( , )
f
f
duf u x
dt
g u x
( )
( )
( , )
0 ( , )
p
p
duf u x
dt
g u x
Programs of PSAPAC-ETMSP
Major Algorithms» Fourth order Runge-Kutta method» Fourth order Gill-Runge-Kutta method» Implicit trapezoidal method
Programs of PSAPAC-ETMSP
0 2 4 6 8 10-200
0
200
400
600
800
1000
1200
seconds
ang
le in d
eg
ree
s
machine angles
An example of unstable case
Programs of PSAPAC-ETMSP
An example of stable case
0 2 4 6 8 100
10
20
30
40
50
60
70
80
90machine angles
seconds
ang
le in d
eg
ree
s
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
Compute the eigenvalues of matrix
0
d uA u B x
dtC u D x
1( )
d uA u
dt
A A BD C
A
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
0.00E+00
2.00E-01
4.00E-01
6.00E-01
8.00E-01
1.00E+00
1.20E+00
0 0.5 1 1.5 2 2.5
Lambda (Transfer Power)
Vo
lta
ge
(p
.u.)
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 ChinaNumber of Generators: 9Number of Bus: 30No. of Zones: 4 (Shanghai, Jiangsu, Anhui, Zhejiang)HVDC converters locate at the Shanghai and Anhui zones (SSZD and NAQD)
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)
Three Gorges Power system
Zone and area names of TGPS
No. Zone name Province or City name Area name1 EE Hubei province Central China2 XX Hunan province Central China3 GG Jiangxi province Central China4 YY Henan province Central China5 SC Sichuan province Sichuan sys.6 SH Shanghai City East China7 JS Jiangsu province East China8 AH Anhui province East China9 ZJ Zhejiang province East China
10 DD HVDC linesBetween Central Chinaand East China
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
IPFLOW Results
Power flow Summary
IPFLOW BPA
Active Power(MW)
Reactive Power(MVAR)
Active Power(MW)
Reactive Power(MVAR)
Generation 97233.8 43340.9 97234.4 43350.7
Load 19125.3 12490.3 19125.3 12490.3
Line andTransformer Losses
858.5 18217.2 860.7 18226.7
Line Charge 0.0 11163.7 0.0 11163.6
Bus Shunt Admittance 77250.0 23797.0 77248.4 23797.3
IPFLOW ResultsIPFLOW BPA
Load Generation Shunt Load
ZoneGeneration
(MW)
Shunt
(MW) (MW) (Mvar) (MW) (MW) (MW)(Mvar
)
AH 7960.0 7536.0 0.0 0.0 7960.0 7535.7 0.0 0.0
DC 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
EE 18159.0 4531.0 6245.3 3453.6 18159.0 4531.4 6245.3 3453.6
GG 3940.0 5239.0 0.0 0.0 3940.0 5239.4 0.0 0.0
JS 139557.3 15499.0 0.0 0.0 13956.9 15499.0 0.0 0.0
SC 14026.0 6435.0 7606.0 4271.7 14026.0 6435.6 7606.0 4271.7
SH 9628.0 11690.0 0.0 0.0 9628.0 11688.6 0.0 0.0
XX 7217.8 8245.0 0.0 0.0 7218.5 8244.6 0.0 0.0
YY 9845.0 6524.0 5274.0 4765.0 9845.0 6523.5 5274.0 4765.0
ZJ 12501.0 11550.0 0.0 0.0 12501.0 11550.6 0.0 0.0
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
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 163-machine
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.