11-grainger-high voltage power electronics
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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
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BackgroundBackground
Technology and Infrastructure ChallengesTechnology and Infrastructure Challenges
Power Electronic TechnologiesPower Electronic Technologies
HVDC SystemsHVDC Systems
FACTS DevicesFACTS Devices
SummarySummary
OverviewOverview
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BackgroundBackground
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BackgroundBackground
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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
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Texas / ERCOT ExampleTexas / ERCOT Example
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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 capacity
with 7.892 GW installed
CREZ Project will add 10 GW
more wind power
2,300 miles of new 345-kV
transmission with shunt and
series dynamic compensation
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Geographic Intensity of Highest Penetration Potential
Renewable ResourcesRenewable Resources
Wind Speed Across the US Solar Intensity Across the US
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Technological and Infrastructure ChallengesTechnological and Infrastructure Challenges
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Issues that are Turbine (Rotating Machine) RelatedTurbine Tripping
Loss in generators can lead to major cascading issues
Subsynchronous Resonance (SSR)
Contributor to turbine shaft damage, SSR results from turbinetensional vibration that is amplified by series capacitors.
Reactive Power ConsumptionInduction 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
Challenges and IssuesChallenges and Issues
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Challenges and IssuesChallenges and Issues
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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 (fuelsource is inherently variable by nature) often resulting in
fluctuations in output voltage.
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Power Electronics Available for ImprovedPower Electronics Available for ImprovedIntegrated Generation Management (IGM)Integrated Generation Management (IGM)
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Power Electronics for IGMPower Electronics for IGM
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Inspiring Quote:
Up until now weve 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. Its a
solution thats starting to be used, but NOWHERE, near to theextent that will be needed in the future. (Wind Directions, 2008)
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Power System BasicsPower System Basics
GenerationMechanical-to-
Electrical EnergyConversion
TransmissionDistribution
Electrical Power Usedand Electrical-to-Mechanical
Energy Conversion
Power Generation, Transmission and Distribution
FACTS / HVDC High Capacity Power Electronics
are applied here for improved operation, reliability, etc.
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Evaluation of AC & HVDC for Future Generation Options
Many of todays 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 futureinfrastructure 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
Power Electronics for IGMPower Electronics for IGM
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HVDCHVDC
HVDC Transmission and HVDC BTB-Link
AC
Network
(A)
AC
Network
(B)
Converter
Station A
Converter
Station B
DCTransmission
Lines
~ or ~
DC-Link
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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)
HVDCHVDC
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Summary Comparison of HVDC Technologies:
HVDCHVDC
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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
HVDCHVDC
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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 toenhance power systems operation and dynamic performance.
FACTSFACTS
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FACTS: Flexible AC Transmission SystemsFunction: Shunt and Series Compensation
Static Var Compensator (SVC) and
Voltage Sourced Converter (VSC-based) STATCOM
Conventional
Mechanically
Switched
SVC
Thyristor
Controlled
STATCOM
Converter
Fast VARs Better, Faster VARsSlow VARs
FACTSFACTS
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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
FACTSFACTS
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Power Electronics TechnologiesPower Electronics Technologies
Voltage Control
Power System Stability
FSC / TCSC
S/S
UPFC
Power Generation
Load
Increased
Transmission Capacity
Inter-area Control
Inter-tie Reliability
Power Flow Control
System Reliability
Improved
Power Quality
Enhanced
Import Capability
Inter-connected
ITC/RTO System
Inter-connected
Power System HVDC / BTB
HVDC / BTB
STATCOM / SVC
S/S
S/S
STATCOM / SVCLoad
Load
Wind Farm
Interconnections
Voltage
Support
BTB DC
SVC /STATCOM
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A View of the Smart Grid
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Summary and ConclusionsSummary and Conclusions
Needs are developing in the electric power sector for improved integratedgeneration 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 controltechnologies 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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