1. 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

2. 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

3. Contents  Background  Procedures of investigating Three Gorges Power System by PSAPAC  Some specific results (comparison with BPA program)  A preliminary view of running PSAPAC

4. 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.

5. 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)

6. 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.

7. 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.

8. 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.

9. 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.

10. 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

11. 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.

12. 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.

13. 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

14. 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

15. 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).

16. Programs of PSAPAC- IPFLOW  Algorithms »Newton method »BX version fast decoupled power flow »XB version fast decoupled power flow »Automatic solution »DC power flow

17. 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.

18. Programs of PSAPAC- ETMSP  DAE systems to be solved For fault-on system For post-fault system

19. Programs of PSAPAC- ETMSP  Major Algorithms »Fourth order Runge-Kutta method »Fourth order Gill-Runge-Kutta method »Implicit trapezoidal method

20. Programs of PSAPAC- ETMSP An example of unstable case

21. Programs of PSAPAC- ETMSP An example of stable case

22. Programs of PSAPAC- SSSP  SSSP Small signal stability program studies the system’s stability in the equilibrium point.

23. Programs of PSAPAC- SSSP  Form linearized DAE system around current equilibrium point  Compute the eigenvalues of matrix

24. 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.

25. Programs of PSAPAC- VSTAB  VSTAB »Capability to automatically determine, from a given operating condition, the nearest point of instability, or maximum loading point.

26. Programs of PSAPAC- VSTAB

27.  Algorithm »Continuation power flow

28. 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.

29. 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

30. 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

31. 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.

32. 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.

33. 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)

34. Data collection and system reduction

35.  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)

36. Data collection and system reduction

37. Three Gorges Power system

38. 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

39. Individual Phase Control (IPF) HVDC model

40. IPFLOW Results

42. ETMSP Results BPA ResultsETMSP Results

43. BPA ResultsETMSP Results

44. 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.

45. 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.

46. Some Suggestions PSAPAC Requires Improvements in the following aspects:  User-friendly interface;  Unified database management;  Graphic output;  Network diagram display.

47. 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.

48. Demonstration

49.  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

50. 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.

51. 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.