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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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 !!

11-grainger-high voltage power electronics

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