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High Voltage Power Electronics Technologies for Integrating Renewable Resources into the Grid

High Voltage Power Electronics Technologies for Integrating Renewable Resources into the Grid RenewElec Workshop Carnegie Mellon University October 22, 2010 – Pittsburgh, PA Dr. Gregory F. Reed & Brandon M. Grainger Power & Energy Initiative

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High Voltage Power Electronics Technologies for Integrating Renewable Resources into the Grid

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  1. High Voltage Power Electronics Technologies for Integrating Renewable Resources into the Grid RenewElec Workshop Carnegie Mellon University October 22, 2010 – Pittsburgh, PA Dr. Gregory F. Reed & Brandon M. Grainger Power & Energy Initiative University of Pittsburgh, Swanson School of Engineering Electrical & Computer Engineering Department

  2. Overview • Background • Technology and Infrastructure Challenges • Power Electronic Technologies • HVDC Systems • FACTS Devices • Summary

  3. Background

  4. Background • Challenges with Renewable Integration • Integration of conventional generation resources (coal, petroleum, and natural gas) and renewable sources (solar and wind) present technological obstacles to the current system and practices • Focus of Work: Characterize common obstacles and present solutions that derive from the interconnection of transmission technologies for better renewable integration • FACTS Compensation Devices for AC Infrastructure Expansion • Conventional and Voltage-Source Converter Based HVDC Transmission Technology • Important Factor: Multiple hybrid configurations can be considered for more economic and reliable grid interconnection

  5. Texas / ERCOT Example • Texas as a Model: Trends to Observe • Generation portfolio consists of traditional fossil generation sources such as coal, petroleum, and natural gas. It also boasts a strong supply of renewable generation, most notably, wind power; and clean nuclear energy • Stands as the U.S. leader in wind generation capacitywith 7.892 GW installed • CREZ Project will add 10 GW more wind power…… • 2,300 miles of new 345-kVtransmission with shunt andseries dynamic compensation

  6. Renewable Resources Geographic Intensity of Highest Penetration Potential Wind Speed Across the US Solar Intensity Across the US

  7. Technological and Infrastructure Challenges

  8. Challenges and Issues • Issues that are Turbine (Rotating Machine) Related • Turbine Tripping • Loss in generators can lead to major cascading issues • Subsynchronous Resonance (SSR) • Contributor to turbine shaft damage, SSR results from turbine tensional vibration that is amplified by series capacitors. • Reactive Power Consumption • Induction generators require substantial amounts of reactive power during operation. This power is pulled from the grid and can cause depressed voltage conditions and stability problems. • Transmission Infrastructure Issues • Power System Dynamic Performance • Moving New/Distant Resource Portfolios to Load Centers • Operations in New Market and Regulatory Conditions

  9. Challenges and Issues • Issues Related to Dispatch of Generation Resources • Voltage Instability • Large differences between the output voltage of the generating utility and grid operating voltage at the point of common coupling can lead to instability on the grid. • Changes in wind speed can contribute to this issue • Voltage Flicker • Wind and solar power generators are non-dispatchable (fuel source is inherently variable by nature) often resulting in fluctuations in output voltage.

  10. Power Electronics Available for Improved Integrated Generation Management (IGM)

  11. Power Electronics for IGM • Inspiring Quote: • “Up until now we’ve just been connecting wind farms to the grid. What we need to be doing is integrating them. Power electronics will enable us to do this by controlling the power flows. It’s a solution that’s starting to be used, but NOWHERE, near to the extent that will be needed in the future.” (Wind Directions, 2008)

  12. DistributionElectrical Power Usedand Electrical-to-Mechanical Energy Conversion GenerationMechanical-to-Electrical EnergyConversion Transmission Power System Basics Power Generation, Transmission and Distribution FACTS / HVDC – High Capacity Power Electronics are applied here for improved operation, reliability, etc.

  13. Power Electronics for IGM • Evaluation of AC & HVDC for Future Generation Options • Many of today’s interconnections make use of high voltage AC transmission to integrate many alternative energies to the electric network. • But is it the most optimal, reliable, and secure option for future infrastructure expansion in all cases? • Renewable resources located further from load centers • There is a distance at which HVDC becomes economically more attractive compared to AC. • Why? AC cable transmission suffers from excessive reactive current drawn by cable charging capacitances. Reactive shunt compensation required to absorb excessive reactive power and avoid overvoltage conditions

  14. HVDC • HVDC Transmission and HVDC BTB-Link DC Transmission Lines ~ or ~ DC-Link ACNetwork(A) ACNetwork (B) ConverterStation A Converter Station B

  15. HVDC • Planning Considerations • Planners should consider the HVDC backbone systems and AC systems with FACTS compensation to achieve the needed capacity and system security. • Two Types of HVDC Technologies • Current-Source Converters (Thyristor Based) • Voltage-Source Converters (Advanced Semiconductor Based)

  16. HVDC Summary Comparison of HVDC Technologies:

  17. HVDC • Advantages of HVDC Systems: • More power can be transmitted more efficiently over long distances by applying HVDC • HVDC lines can carry 2 to 5 times the capacity of an AC line of similar voltage • Interconnection of two AC systems, where AC lines would not be possible due to stability problems or both systems having different nominal frequencies • HVDC transmission is necessary for underwater power transfer if the cables are longer than 50km • Power flow can be controlled rapidly and accurately

  18. FACTS • FACTS: Flexible AC Transmission Systems • Greater demands are being placed on the transmission network and will continue. At the same time, its becoming more difficult to acquire new rights of way for new transmission infrastructure/lines. • FACTS open the door for new opportunities in controlling power, enhancing the usable capacity of present and future transmission; improving system performance, reliability and security; and validating the use of power electronics to enhance power systems operation and dynamic performance.

  19. FACTS • FACTS: Flexible AC Transmission Systems • Function: Shuntand Series Compensation • Static Var Compensator (SVC) and Voltage Sourced Converter (VSC-based) STATCOM Fast VARs Better, Faster VARs Slow VARs

  20. FACTS • Advantage of FACTS Devices • Efficient Installations: 12 to 18 month timeframe • Increased System Capacity:Maximum operational efficiency of existing transmission lines and other equipment • Enhanced System Reliability: Provide greater voltage stability and power flow control, which improves system reliability and security • Improved System Controllability: Intelligence built into the grid, ability to instantaneously respond to disturbances & redirect power flows • Investment: Less expensive than new transmission lines

  21. Inter-connected ITC/RTO System S/S HVDC / BTB UPFC Power Generation Wind FarmInterconnections Voltage Control Power System Stability Power Flow Control System Reliability Inter-area Control Inter-tie Reliability Enhanced Import Capability VoltageSupport BTB DC S/S Load SVC /STATCOM Load STATCOM / SVC STATCOM / SVC Increased Transmission Capacity Improved Power Quality HVDC / BTB Load Inter-connected Power System S/S FSC / TCSC Power Electronics Technologies • A View of the Smart Grid

  22. Summary and Conclusions • Needs are developing in the electric power sector for improved integrated generation management (IGM) with respect to the increase in green energy resource penetration. • Many of the challenges faced for IGM and the new green resource portfolios that are emerging are within the power transmission delivery sector. There is a strong need for applying advanced transmission technologies to assure safe, reliable, and efficient electricity delivery. • Future applications and development requirements for power electronics and control technologies in a diversified generation environment, with respect to power system dynamic performance, are needed. • In general, the case is made for employing more power electronics control technologies throughout transmission and distribution systems for strategically interconnecting green energy resources. • Combinations of FACTS and HVDC transmission technologies can provide optimal solutions and enhanced investment for utilities and generation providers alike – we need continued development and deployment !!

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