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.)

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 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

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

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

Individual Phase Control (IPF) HVDC model

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

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 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.