Strategic Location of Renewable Generation Based on Grid Reliability

1. Strategic Location of Renewable Generation Based on Grid Reliability PowerWorld Users’ Group Meeting November 2-3, 2005 The CALIFORNIA ENERGY COMMISSION and DAVIS POWER CONSULTANTS contributed to the development of this analysis. Davis Power Consultants

2. Strategy • Identify links between electricity needs in the future and available renewable resources. • Optimize development and deployment of renewables based on their benefits to: • Electricity system • Environment • Local economies • Develop a research tool that integrates spatial resource characteristics and planning analysis.

3. Objectives • Investigate the extent to which renewable distributed electricity generation can help address transmission constraints • Determine performance characteristics for generation, transmission and renewable technology • Identify locations within system where sufficient renewable generation can effectively address transmission problems

4. Objectives • We want to determine the impact of large-scale distributed projects on grid security. • We need to: • Identify weak transmission elements and define metrics that assess system security. • Find locations where new generation would enhance the security of the grid. • Combine maps of beneficial locations with maps of energy resources.

5. Methodology • Simulation • Power Flow • Contingency Analysis • Security Metrics • Results • Weak Elements • Security Indices • Visualization

6. Power flow Simulation • Identify weak elements in the system by simulating impacts from lost transmission or capacity (NERC N-1 contingency) • More importantly, can identify locations in system where new generation can provide grid reliability benefits.

7. Normal Operation Example System does not have normal operation thermal violations

8. Contingency Example Suppose there is a fault and this line is disconnected Then this line gets overloaded (is a weak element) This is a serious problem for the system Planning Solutions: New line to bus 3 OR New generation at bus 3

9. Contingency Analysis • Security is determined by the ability of the system to withstand equipment failure. • Weak elements are those that present overloads in the contingency conditions (congestion). • Standard approach is to perform a single (N-1) contingency analysis simulation. • A ranking method will be demonstrated to prioritize transmission planning.

10. Then multiply by limit to get the Aggregate MW Contingency Overload (AMWCO) Sum each value-100 to find the Aggregate Percentage Contingency Overload (APCO) Results Organized by Lines, then Contingencies

11. AMWCO 28 21 14 7 0 Weak Element Visualization

12. Overloaded Line in this direction Transfer helps mitigate the overload by means of a counter-flow Sink New Source Determination of Good Locations

13. Determination of Good Locations • Generation could be located to produce counter-flows that mitigate weak element contingency overloads. • The new injection of power requires decreasing generation somewhere else. • A good assumption is that generation will be decreased across the system or each control area using participation factors.

14. TLR for Normal Operation • Need to know how the new generation at a certain bus will impact the flows in a transmission element. → Transmission Loading Relief (TLR) → Since a TLR is calculated for every bus, the TLR can be used to rank locations that would be beneficial for security.

15. Specify the sink of the transfer Specify the weak transmission element Sensitivities are calculated for each bus

16. TLR for Contingencies • Need to consider contingencies • Contingency Transmission Loading Relief (TLR) Sensitivity is the change in the flow of a line due to an injection at a bus assuming a contingency condition.

17. Determination of Good Locations • Equivalent TLR (ETLR):

18. Determination of Good Locations • Weighted TLR (WTLR) using post-contingency TLRs: • Weighted TLR (WTLR) using base case TLRs:

19. Contingencies WTLR Weak Elements Buses Buses Weighted TLR (WTLR) • Complexity: A TLR is computed for each bus, to mitigate a weak element, under a contingency. • We want a single “weighted” TLR for each bus.

20. Contingencies Weak Elements Weak Elements Buses Buses Calculating WTLRs • The contingency information (severity and number) of a weak element can be captured by calculating the Aggregate MW Contingency Overload (AMWCO). • This effectively converts the cube to a table.

21. WTLR Weak Elements Buses Buses Calculating WTLRs • Need to mitigate the weakest elements first • Weight the TLR by the weakness of each element, which is given by the AMWCO.

22. Meaning of the WTLR • A WTLR of 0.5 at a bus means that 1MW of new generation injected at the specific bus is likely to reduce 0.5 MW of overload in transmission elements during contingencies. • Thus, if we inject new generation at high impact buses, re-dispatch the system, and rerun the contingencies, the overloads will decrease. • Note that the units of the WTLR are:

23. Large Case Example • Project for the California Energy Commission (CEC). • Needed to simulate N-1 contingencies (about 6,000 for California) • Simulation developed for 2003, 2005, 2007 and 2017 summer peak cases. • In 2003, there were 170 violating contingencies, 255 contingency violations, and 146 weak elements.

24. Process Overview Test Power Injections at Select Locations Identify Weak Elements Evaluate Locations (WTLR) GIS Overlay Power Flow Cases

25. 400 APCO 2003 2005 2007 350 300 250 200 150 100 50 # Weak Elements 0 0 20 40 60 80 100 120 140 160 180 200 220 240 Result: Weak Element Distribution Both number and weakness of elements increase with time

26. Identification of Weak Elements 2007 2017 The spatial distribution of weak elements seems to follow an identifiable pattern.

27. Good Locations • New generation at green locations will tend to reduce the overloads. • New generation at red-yellow locations will tend to increase the overloads. • Note that higher imports would worsen system security.

28. WTLR Local WTLR Visualization

29. Eastern Interconnection WTLR 1.50 0.75 0.00 –0.75 –1.50

30. Towards a Locational Value • Determination of locations where new generation would enhance security needs to be combined with availability and economics of energy resources. • Valuation requires monetizing the security benefits.

31. Towards a Locational Value • GIS spatial analysis techniques are needed to determine feasible generation alternatives for each location in a large-scale system. • Based on existing energy potential and technology, a least-cost alternative can be determined for each location.

32. Towards a Locational Value • Units of WTLR are [AMWCO/MW installed]. • The security cost/benefit can be obtained as follows: • Assume WTLR is negative: Injection reduces the AMWCO

33. Security-Penetration Curves • Once a set of proposed sites is defined, the effect of simultaneous distributed injections with different levels of penetration can be simulated using security-penetration curves. • The effectiveness of the solution is affected for large injections due to: • Local transfer capability of the grid • Reversed flows

34. Security-Penetration Curves SysAMWCO in 2005 12,000 10,000 8,000 69 500 115 6,000 230 4,000 2,000 0 0 650 1300 2000 New Generation

35. Policy Analysis • A fundamental goal of integrated electricity systems is to ensure dependable supply to customers. • This goal cannot be achieved if the system consistently exhibits overloaded elements and congestion. • System AMWCO can be utilized to: • Evaluate system security for different seasons/years • Design policy goals regarding security • Can use security-penetration curves

36. Indicates how much generation is needed to maintain the current level of reliability. Approx. 500MW every two years (at strategic locations) Policy Analysis Indicates the effect of new generation Approx. -3.5 MWCO/MW Installed NewGen AMWCO

37. Generation needed to maintain the current level of reliability. Policy Analysis 7300 Generation needed in the next two years (2005) to solve the problems by 2017. Approx. 950MW

38. Integrated Model Power Flow Model Energy Resources WTLR Calculation Maps of Energy Potential Contingency Analysis Spatial Rep. of New Generation Weak Element Ranking GIS Spatial Overlay Security Indices Security- Penetration Curves List of Proposed Sites Generation Expansion Transmission Expansion Energy Policy Transmission Policy