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

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24 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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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



Background



Technology and Infrastructure Challenges



Power Electronic Technologies



HVDC Systems






FACTS Devices



Summary

Overview

2

Background

3

Background

4

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


Texas / ERCOT Example

5

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


6

Geographic Intensity of Highest Penetration Potential

Renewable Resources

Wind Speed Across the US

Solar Intensity Across the US

Technological and Infrastructure Challenges

7

8

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



Challenges and Issues

Challenges and Issues

9

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
.


Power Electronics Available for Improved

Integrated Generation Management (IGM)

10

Power Electronics for IGM

11

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)


Power System Basics

Generation

Mechanical
-
to
-

Electrical Energy

Conversion

Transmission

Distribution

Electrical Power Used

and Electrical
-
to
-
Mechanical
Energy Conversion

Power Generation, Transmission and Distribution

FACTS / HVDC


High Capacity Power Electronics

are applied here for improved operation, reliability, etc.

12

13

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


Power Electronics for IGM

HVDC

HVDC Transmission and HVDC BTB
-
Link

AC

Network
(A)

AC

Network
(B)

Converter

Station A

Converter
Station B

DC
Transmission
Lines

~ or ~

DC
-
Link


14

15

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)




HVDC

16

Summary Comparison of HVDC Technologies:




HVDC

17

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




HVDC

18



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.

FACTS

19



FACTS: Flexible AC Transmission Systems



Function:
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 VARs

Slow VARs

FACTS

20



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



FACTS

Power 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 / SVC

Load

Load

Wind Farm

Interconnections

Voltage

Support

BTB DC

SVC /

STATCOM

21

A View of the Smart Grid

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 !!

22