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Germany Takes the Lead in HVDC
Alex Narimatsu Bernardi André Cançado Valério
07.06.13 - Dresden, Germany
New developments in high-voltage DC electronics could herald an epic shift in energy delivery
March, 2011 - Fukushima
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Germany
“The idea for HVDC lines started to gain traction two years ago, when the Fukushima nuclear accident in Japan led German chancellor Angela Merkel to shut down 8 of her country’s 17 nuclear reactors and revive plans to phase out the rest of them by 2022.”
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Germany
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Why not generate in the South
• Winds are generally slower in the south
• Resistance from environmental groups against new hydropower reservoirs
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Philippsburg
Borkum Island
Corridor A: 1000 MW
660 Km
What is HVDC
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Advantages of HVDC
• is more economic for transmitting large amounts of power point-to-point over long distances;
• HVDC schemes can transfer power between separate AC networks.
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IUP
2IRPJ A
LR
Disadvantages of HVDC
• The converters required at both the ends of the line are very expensive.
• The converters produce lot of harmonics.
• Converters have very little over load capacity and absorb considerable amount of reactive power.
• Circuit breaking in multi-terminal dc systems is difficult and costlier.
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HVDC Records
Classic HVDC lines use converters(AC-DC and DC-AC) built from thyristors which are efficient but limited in their capabilities.
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HVDC Records
• In the late 1990s ABB commercialized more sophisticated and compact converters, built from high-frequency silicon insulated-gate bipolar transistors (IGBTs). These “voltage source converters” (VSCs) control their own voltage and can thus help stabilize the AC grid around them.
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HVDC Records
• But the IGBT-based converters still had three hurdles to overcome before they could challenge AC technology:
1. Low capacity ceiling
2. High switching losses(about 1.5 to 2% of transmitted
power per converter)
3. Inability to break DC current.
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HVDC Records
• In 2010, Siemens commercialized a IGBT converter(“Modular Multilevel Converter”) that cleared the two firsts hurdles: 1. converter capacity of 1000 MW or more
2. switching losses to just 1 percent per converter.
• But the 3rd hurdle stills. 3. Inability to break DC current.
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Solutions
• Alstom
• Siemens + Rainer Marquardt (University of Federal Defense-Munich)
• ABB
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• Solution - redesign the AC-DC converter submodules to function as breakers, doubling the number of IGBTs to create a “full-bridge submodule.”
• Status - In February, Alstom demonstrated a converter incorporating full-bridge submodules that extinguished DC currents exceeding 3000 amperes in less than 2.5 milliseconds
• Problem - low efficiency, losses from each converter of as much as 1.7 percent.
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• Solution - An extra equipment to realize the HVDC breaking
• Status – November, ABB demonstrated an entirely novel solution to efficient HVDC breaking: a stand-alone breaker that would sit on the HVDC line and be used along with the standard, two-IGBT converter.
A fast breaker(5 ms) and without efficiency problems.
• Problem – High Costs
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• Solution - connect two of the submodules used in
Modular Multilevel Converter with a fifth IGBT. It works like a full bridge converter but only three of the five IGBTs are conducting at any given moment. Resulting in 1/3 less losses comparing with a full bridge converter.
• Status - Siemens has not revealed its plans for this design,
but Marquardt, the creator, says it won’t be hard to implement, because his new sub modules are essentially a drop-in replacement for those Siemens already sells.
• Problem – still not tested.
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Future…
These HVDC innovators have to move fast.
The Corridor A is already in public consultation phase and is set to start carrying power in 2017.
“The schedule is very tough” -
Large scale grid schemes are being studied. And the Corridor A could be the 1st step of a European super grid.
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References
• http://spectrum.ieee.org/energy/renewables/germany-takes-the-lead-in-hvdc
• http://www.dciinsulator.com/shownews.asp?id=155
• Eletrônica de Potencia, Pomilio J.A. – Universidade Estadual de Campinas - 1998
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Thank You!
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