germany takes the lead in hvdc - tu dresden · •solution-an extra equipment to realize the hvdc...

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

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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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