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EXPANSION OF TRANSMISSION SYSTEMS IN A DEREGULATED ENVIRONMENT

EXPANSION OF TRANSMISSION SYSTEMS IN A DEREGULATED ENVIRONMENT. Yong Zheng Saskatchewan Power Corporation. N.A.Chowdhury University of Saskatchewan. Regulation:. Regulated Monopoly. Deregulation:. Re-structuring of the Market. Re-regulation. Deregulation. Competition.

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EXPANSION OF TRANSMISSION SYSTEMS IN A DEREGULATED ENVIRONMENT

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  1. EXPANSION OF TRANSMISSION SYSTEMSIN A DEREGULATED ENVIRONMENT Yong Zheng Saskatchewan Power Corporation N.A.Chowdhury University of Saskatchewan

  2. Regulation: Regulated Monopoly Deregulation: Re-structuring of the Market Re-regulation

  3. Deregulation Competition Unbundling of Services Privatization Open access

  4. Electrical Industry Regulation and Deregulation Traditional regulated System Model Deregulated System Model Generation Transmission Distribution Retail Sale Generation Company Transmission Company Distribution Company Retailers Customers Customers Generation & Retailing - Deregulated Transmission & Distribution - Regulated Monopoly Franchise Limited Benefit Return

  5. GOALS OF DEREGULATION • Lower utility rates • Choice of electricity providers • Efficient, cost based pricing • Encouraging renewable energy sources • Customer specific services

  6. $20/MW Load1 Power Flow: 90MW G1 60MW Line1 Limit: 80MW 150MW 0MW 90MW G2 Load2 $40/MW Transmission System Congestion Transmission system congestion means that one or several transmission lines in the system are overloaded.

  7. Transmission System Congestion The introduction of competition in electric power market has made power flow control issues more complex and difficult than ever before. The scarcity of transmission capacity and a continued demand for power from less expensive sources lead to transmission system congestion.

  8. Causes of Congestion • Market participants are blind to system operating conditions • Generation schedule is determined by competitive market • System operator has no right to interfere with market-based generation schedule unless congestion occurs

  9. Consequences of Congestion • Unsolved congestion will threaten system security • Congestion relief will increase system operating cost • Congestion will bring extra cost to electrical users • Congestion will hinder fair competition between generators

  10. Ways to Relieve Congestion • Generation reschedule • Interruptible load curtailment • Transmission system expansion

  11. $20/MW Power Flow: 80MW Load1 G1 Line1 Limit: 80MW 60MW 110MW New Added Line 40MW 90MW G2 Load2 $40/MW Congestion Relief

  12. Research Objectives • To develop methods to optimize generation re-schedule when congestion happens • To include the effect of short-term power market on transmission network expansion • To assess several alternatives to find the optimal transmission expansion in case of congestion

  13. Optimization of Generation Reschedule • Mathematical Model of Optimum Generation Reschedule • AC Optimal Method

  14. Mathematical Model for Re-dispatch Objective Function: Subject to Ci=re-dispatch price submitted by Generator i DPGi =active power variation of Generator i DPL =change in transmission loss n =number of generators

  15. AC Optimal Method • Based on AC power flow method • Linearized relationship between power flow variation and generation variation • Linearized relationship between transmission loss variation and generation variation • Takes transmission loss into account

  16. A System with Three Transactions

  17. Reloading Bids

  18. Active power flows before and after re-dispatch The increased cost due to the re-dispatch is $954.384/hr.

  19. Load function can be expressed as: P(t) = Q0 + Q(t) + Q(r); t = 1, 2, 3, ……, 24 Q0and Q(t) are non-price responsive parts Q(r) is the price responsive part Load Model

  20. Bidding Model Benefit Function can be expressed as: B(PGi) = F(PGi) + M(PGi) Cost function: F(PGi) = PGi2+ PGi +  Profit function: M(PGi) = k* PGi Bidding price function: H(PGi) = B(PGi)/PGi= 2PGi +  + k

  21. Total generating cost as seen by the ISO Market Clearing Price, r can be found by solving

  22. Bidding Price Curve

  23. Transmission System Expansion • Expanding transmission system is more economic if congestion fee is higher than the investment cost of building new transmission line. • Future short-term power market should be considered when planning transmission system expansion. • Different expansion options should be assessed when selecting the most acceptable expansion scheme.

  24. Steps involved in transmission system expansion planning • Forecast short-term market generation schedule on the basis of typical load curves and bidding price functions. • Combine the predicted short-term generation schedule with long-term generation schedule to evaluate system power flow distribution and congestion fee. • Select new lines that can relieve congestion with investment cost less than congestion fee.

  25. Summary and Conclusions • Deregulation makes power flow control more complicated • Market-driven generation schedule results in transmission system congestion • Congestion will threaten system security and must be relieved • Generation reschedule will increase system operating cost • Expansion of transmission becomes economic if the investment cost of building new transmission facilities is less than the congestion fee.

  26. Question?

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