Lindsey Hopf Andrew Letsinger Carl Reed Brandon Kelley Tong Wu Keith McKenzie
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November 1, 2013
Presentation Outline • History and Basic Theory
• State-of-the-art Designs/Products
• Impacts (Technical and Social)
• Challenges or R&D Focus
• True Stories of Application/Demonstration
• Recent Research
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Presenter
Presentation Notes
History and basic theory of the technology: Lindsey Hopf State-of-the-art designs/products: Andrew Letsinger Impacts (technical and social): Carl Reed Challenges or R&D focus in next 5-10 years: Brandon Kelley 1-2 true (successful or not) stories of its application or demonstration: Tong Wu 1-2 related research papers published in recent 5 years: Keith McKenzie
History
• Early as 5000 B.C.
• 1890 – First wind turbine
• 1940s – “Grandpa’s Knob”
• Mid-1940s - 1970s – Decline in interest in wind turbines
• 1970s – Increase in interest in wind turbine generators
• Now – World’s fastest growing energy source 3
Basic Theory
• Harness energy through wind’s momentum
• Wind’s momentum turns blades
• Blades turn the turbine
• Turbine turns generator
• Transformers step up voltage from generator
• Power flows to a substation which connects to a transmission line
History and basic theory of the technology: Lindsey Hopf State-of-the-art designs/products: Andrew Letsinger Impacts (technical and social): Carl Reed Challenges or R&D focus in next 5-10 years: Brandon Kelley 1-2 true (successful or not) stories of its application or demonstration: Tong Wu 1-2 related research papers published in recent 5 years: Keith McKenzie
Enercon E-126
• Enercon built • 7.58 MW power output • Total height: 198m (650ft) • Total weight: 6,000t • Cost: €11,000,000
History and basic theory of the technology: Lindsey Hopf State-of-the-art designs/products: Andrew Letsinger Impacts (technical and social): Carl Reed Challenges or R&D focus in next 5-10 years: Brandon Kelley 1-2 true (successful or not) stories of its application or demonstration: Tong Wu 1-2 related research papers published in recent 5 years: Keith McKenzie
Technical Advantage
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• Chart uses most conservative estimates
• Others cite Wind at 0.02 pounds CO2 / kWh
• Coal estimates as high as 3.6 and natural gas as high as 2 pounds CO2/ kWh
Presenter
Presentation Notes
Using the most conservative estimates of life-cycle emissions (measured in CO2(lbs.)/kWh), Wind power produces a small fraction of emissions compared to coal and natural gas. Why does Wind have any emissions at all? Life-cycle emissions factor in the CO2 used in the production of the steel and concrete for the turbines, as well as the energy used to prepare and maintain wind turbines/sites. Aside from reducing greenhouse gas emissions, leveraging wind energy has the effect of decreasing mercury and heavy metal air emissions, pollution related to the extraction and transportation of fossil-based fuels, lake and streambed acidification from acid rain and mining, and reducing water consumption related to coal and natural gas applications.
Technical Disadvantage
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• Distributing wind farms smooths output power
• Smoother output curves, less output variability
• Less variability, less cycling costs
Source: International Energy Agency
Presenter
Presentation Notes
One of the biggest problems facing wind energy is its innate variability: when the wind isn’t blowing, turbines generate no electricity. The variability can be treated to a certain degree if wind turbines are distributed across a large enough geographic distance. There’s also the problem of wind power transmission. Generally, the wind power candidate sites with the highest wind speed, and highest wind energy density happen to be far from areas of power consumption (cities and industrial centers). Therefore, in order to use the power generated from the turbines, expensive infrastructure must be invested in and maintained to transmit wind power.
Technical Impact
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Presenter
Presentation Notes
Despite large improvements in recent years, coal power is overall, still slightly cheaper than wind (OpenEI database gives numbers $40/MWh for coal (unscrubbed and unpulverized) compared to $60/MWh for wind power). However, wind power is much easier to budget for considering the static nature of the costs involved. Where most of the cost from fossil-fueled generation is related to fluctuating fuel costs, the largest costs involved with wind power generation are fixed (installation followed by transmission).
Environmental Impact
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Presenter
Presentation Notes
One of the most publicized environmental impacts of wind power is the increased avian mortality rate. Bird and bat populations alike may suffer from installed wind turbines. It’s important to note though, most studies show that other human activities interfere with avian mortality rates to a larger degree than wind farms. Still, it’s important to consider wildlife habitation and mortality, especially when installing turbines close to areas that are inhabited by endangered or sensitive species. Another way to mitigate especially bat deaths, is to increase the cut-in speed of wind turbines. It’s been documented that bats usually only fly at lower wind speeds, so by increasing the cut-in speed, collisions can be decreased without a substantial loss in power generation (~1%).
Social Impact
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Presenter
Presentation Notes
Largest social challenge many wind farms face involves the close-area effects of wind turbines: EM interference, visual impact, shadow flicker, and ice throw. Especially in America, some communities may offer a lot of resistance to wind power because they believe the turbines are a blight on the local scenery. Others have claimed that the noise from the turbines (which depends largely on both turbine design and wind speed) is unbearable or negatively impacts health, however, industry and government sponsored studies in Canada and Australia have concluded that these issues do not adversely effect public health. Still, the solution to these problems is to have a public discussion and weight the merits of cleaner technology against the potential setbacks.
The most important factor in wind power is location. Most of, if not all, of the negative social and technical impacts can be mitigated through careful land planning and site selection/preparation. It’s important to know about and understand on a general level, all of the impacts related to wind power so we can design and plan implementations that limit the negative effects like avian mortality and community conflict, while increasing the efficiency and overall output by wind farms and turbines.
Presentation Outline • History and Basic Theory
• State-of-the-art Designs/Products
• Impacts (Technical and Social)
• Challenges or R&D Focus
• True Stories of Application/Demonstration
• Recent Research
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Presenter
Presentation Notes
History and basic theory of the technology: Lindsey Hopf State-of-the-art designs/products: Andrew Letsinger Impacts (technical and social): Carl Reed Challenges or R&D focus in next 5-10 years: Brandon Kelley 1-2 true (successful or not) stories of its application or demonstration: Tong Wu 1-2 related research papers published in recent 5 years: Keith McKenzie
Disadvantages (Onshore)
• Reliability/Efficiency • Wildlife • Noise • Aesthetics • Geography • Land Use
Disadvantages (Offshore)
• Price To Build • Hurricane Force Winds • High Risk • Price For Customers ($1850/KWh) • Elements
History and basic theory of the technology: Lindsey Hopf State-of-the-art designs/products: Andrew Letsinger Impacts (technical and social): Carl Reed Challenges or R&D focus in next 5-10 years: Brandon Kelley 1-2 true (successful or not) stories of its application or demonstration: Tong Wu 1-2 related research papers published in recent 5 years: Keith McKenzie
Overall review of China's wind power industry: status quo, existing problems,
and prospective for future development
Background
• Reduce CO2 emit/GDP – 40-50% by 2020 • Strategy • By May 2012, total capacity – 50.26 GW
Two Concepts
• Integrated capacity • Installed capacity
• Gap – Local consumption and transmission
Critical Problems
• Low grid access • LVRT incapability of wind turbine • Distribution mismatch between resources and
power consumption • Misalignment between wind power planning and
• Promote the market of equipment and increase the utilization of wind power
• Ease the contradiction between wind farms and power grid
• Lay a foundation for China’s future
Future Development
• In the past
• Switch to the large consumption places • Slow down large scale wind farm • More distributed and small-scaled installation
Future Power Market
• Short term, main grid will support the distributed power
• Long term, owner of the distributed power can trade power with main grid
• Long-distance transmission-HVDC
• Connection with the HV/extra HV grid – ”Strong Smart Grid”
Conclusion
• At the fast-developing period • Face several problems:
– Low grid access – Operation problems – Economic loss
• 2 points to achieve:
– Shift from concentrated construction to distributed development
– Enhance the transmission capacity
Presentation Outline • History and Basic Theory
• State-of-the-art Designs/Products
• Impacts (Technical and Social)
• Challenges or R&D Focus
• True Stories of Application/Demonstration
• Recent Research
29
Presenter
Presentation Notes
History and basic theory of the technology: Lindsey Hopf State-of-the-art designs/products: Andrew Letsinger Impacts (technical and social): Carl Reed Challenges or R&D focus in next 5-10 years: Brandon Kelley 1-2 true (successful or not) stories of its application or demonstration: Tong Wu 1-2 related research papers published in recent 5 years: Keith McKenzie
Low Voltage Ride Through (LVRT)
• Needed to avoid catastrophic cascade tripping of wind turbines. • FERC Order 661A (2005).
– 3-phase fault with normal clearing (up to 9 cycles). – Single line to ground fault with delayed clearing (24 cycles).
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Presenter
Presentation Notes
In the Spanish power grid, several cascading events did occur during the first few months of 2004, resulting in wind generation losses ranging from 400 to 600 MW. Voltage is measured at the high side of the wind turbine step-up transformer (or interconnection step-up transformer for wind plants). Picture source: Zavadil, R.; Miller, N.; Ellis, A.; Muljadi, E.; Camm, E.; Kirby, B., "Queuing Up," Power and Energy Magazine, IEEE , vol.5, no.6, pp. 47-58, Nov.-Dec. 2007.
Magnetic Amplifier
• Magnetic amplifier is essentially a saturable reactor. • Each core links with 2 windings: ac winding and control winding.
– Sufficient dc current (ic) in control winding, core saturates (point A). – Adjust ic such that core operates in linear region (point B).
• “Amplifier” since small change in ic causes large change in ia.
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Presenter
Presentation Notes
The magnetic amplifier in the figure consists of 2 cores. They are connected in opposite phase in order the cancel the effects the ac winding current has on the control winding. Point A: Impedance seen by ac winding is low (normal operation). Point B: Impedance seen by ac winding is high.
PMSG WT with Magnetic Amplifiers
• Magnetic amplifiers in series between PMSG and diode rectifier.. • Each phase split into two windings to avoid demagnetization of
magnetic amplifier during negative half cycle of supply voltage.
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Presenter
Presentation Notes
Magnetic amplifiers are used here as method of series compensation. The control winding current can be used to change the main winding effective impedance. Rectifying diodes help the magnetic amplifier cores reach saturation faster.
Simulation #1: No Magnetic Amplifiers
• Voltage dips of 30%, 60%, and 90% at 0.4 s, 0.8 s, and 1.2 s. • Power from wind turbine has no where to go but dc link capacitor. • When voltage dips 90%, dc link voltage approaches 2 pu. 33
DC Link Voltage
IGBT Voltage
Presenter
Presentation Notes
Even though the grid power drops due to the voltage dips, the PMSG continues to extract maximum power. High dc link voltage may result in severe damage to the VSI.
Sim. #2: Magnetic Amplifiers Included
• Voltage dip of 90% at 0.5 s. • Control winding PI controller senses rise in dc link voltage. • Change in dc link voltage reduced dramatically. 34
DC Link Voltage
IGBT Voltage
Presenter
Presentation Notes
Magnetic amplifier operating point shifts from point A (saturation) to point B (linear), resulting in a high voltage drop across the ac winding. Rise in dc link voltage <10%. One question that is not clearly answered in the paper is where does the mechanical power of the wind turbine go following the voltage dip? Is it absorbed by allowing the generator to speed up? Unfortunately, no plot of the generator speed is provided.
