Siemens AG Power Transmission Solutions J. Dorn, … · Siemens AG Power Transmission Solutions J. Dorn, ... 115 kV . Substation. ... Further Design Aspects:

Cigre Colloquium on HVDC and Power Electronics SystemsMarch 7 through 9, 2012

CIGRE Colloquium on HVDC and Power Electronic Systems Wednesday March 7 through Friday March 9, 2012

Hotel Nikko, San Francisco, California, USA

Trans Bay Cable –

A Breakthrough of VSC Multilevel Converters in HVDC Transmission

Siemens AG

Power Transmission Solutions

J. Dorn, [email protected]


Content

Overview

Operational Experience

Further Development Aspects

Impressions of Trans Bay Cable


►

Overview





Trans Bay Cable -

The Initial Situation

Situation before Trans Bay Cable: Bottlenecks in the Californian

grid

Problem: No right of way for new lines or land cables

The solution:


Trans Bay Cable –

Key Data

Pittsburg Substation

Potrero Substation

< 1 mile 53 miles1 mile 1 mile < 3 miles

San Francisco Pittsburg

Cables

AC/DCConverter

Station

Cables

AC/DCConverter

Station

ACAC

115 kV Substation

230 kV Substation

•

Converter: Modular Multilevel HVDC PLUS Converter•

Rated Power: 400 MW @ AC Terminal Receiving End•

DC Voltage: ±

200 kV•

Submarine Cable: Extruded Insulation DC Cable•

Start of Commercial Operation November 2010

• Converter: Modular Multilevel HVDC PLUS Converter• Rated Power: 400 MW @ AC Terminal Receiving End• DC Voltage: ±

200 kV• Submarine Cable: Extruded Insulation DC Cable• Start of Commercial Operation November 2010

Submarine DC Cables


HVDC PLUS

Modular Multilevel Converter –

Basic Scheme

SM 1

SM 2

SM n

SM 1

SM 2

SM n

SM 1

SM 2

SM n

SM 1

SM 2

SM n

SM 1

SM 2

SM n

SM 1

SM 2

SM n

Ud

Phase Unit

SM


Overview

►





Operational Experience:

AC Under-Voltage Fault



Step Response in terms of Converter Arm Energies

Step Response of vertical balancing control in terms of converter arm energies.

No influence on AC currents!

-1,5

-1

-0,5

0

0,5

1

1,5

0,05 0,07 0,09 0,11 0,13 0,15 0,17 0,19 0,21 0,23 0,25

Zeit t [s]

Ein

gang

s- u

nd A

usga

ngss

trom

i [p

u]

0,6

0,65

0,7

0,75

0,8

0,85

0,9

0,95

1

0,05 0,07 0,09 0,11 0,13 0,15 0,17 0,19 0,21 0,23 0,25

Zwei

gene

rgie

w [p

u]

AC

Cur

rent

s (n

orm

aliz

ed)

Con

vert

er A

rm E

nerg

ies

(nor

mal

ized

)

Time (sec)


-1,5

-1

-0,5

0

0,5

1

1,5

0,25 0,27 0,29 0,31 0,33 0,35 0,37 0,39 0,41 0,43 0,45

Zeit t [s]

Ein

gang

s- u

nd A

usga

ngss

tröm

e i [

pu]

AC

Cur

rent

s(n

orm

aliz

ed)

0,6

0,65

0,7

0,75

0,8

0,85

0,9

0,95

1

0,25 0,27 0,29 0,31 0,33 0,35 0,37 0,39 0,41 0,43 0,45

Zwei

gene

rgie

n w

[pu]

Con

vert

er A

rm E

nerg

ies

(nor

mal

ized

)

Time (sec)

Step Response of horizontal balancing control in terms of converter arm energies.

No influence on AC currents!


Step Response in terms of Converter Arm Energies


Equivalent disturbing current in the range from 60 Hz to 5.1 kHz.


Harmonics: Converter phase to ground voltages



Harmonics: DC current

Total harmonic distortion of converter phase to ground voltages in the range from 120 Hz to 3 kHz clearly below 1%.



Losses

Total losses between the two AC systems within the specified limits.


Overview


►




Further Development Aspects:

Increase of Current Capability

Half Bridge Submodule with parallel connection of IGBTs to increase the current capabability



Full Bridge Submodules

•

AC voltage instead of DC voltage possible

•

DC pole-to-pole fault can be turned off by IGBTS

•

Higher losses compared to half bridge submodules

SM 1

SM 2

SM n

SM 1

SM 2

SM n

SM 1

SM 2

SM n

SM 1

SM 2

SM n

SM 1

SM 2

SM n

SM 1

SM 2

SM n

u



Clamp-Double Submodule

•

Double voltage capability compared to half bridge submodule and full bridge submodule

•

Capability to turn off a DC pole-to-pole fault with IGBTs

but

•

Lower losses than full bridge Submodule


Further Design Aspects:

Requirements for Offshore Wind Grid Access

Main goal: Keep windfarm operational at all costs / prevent wind

turbine shutdown

Wind turbines have only 100 ... 200ms Fault Ride Through (FRT) capability

Onshore Grid Codes, however, require interruption capability of > 1s

Windfarm output power has to be kept up during this period

There are no feasible means of storage for the excess power, so where to put it?



Braking Chopper Submodule for Grid Access

Possible solution: DC braking chopper

absorbs dynamic excess power generated by the windfarm during onshore grid interruptions

For enduring grid faults, the windfarm may be throttled down in usual order, via windfarm power control –

no emergency shut-down

The chopper is installed at the onshore converter station,the offshore station‘s footprint is not enlarged.

Windfarm will take no notice of short onshore grid interruptions



Series Connection of Power Semiconductors

Usually, a semiconductor device failure does not lead to a discharge of the capacitor.

But:

•

A faulty semiconductor has to have the capability for load current

•

Or: Bypass device

•

Short circuit of a whole half bridge shall be considered (impact on neighbored submodules)


Overview



►



Trans Bay Cable Some Impressions


Trans Bay Cable Some Impressions


Trans Bay Cable DC Yard


Trans Bay Cable AC Yard


Trans Bay Cable Converter Hall


Thank you very muchfor your attention!

Thank you very muchThank you very muchfor your attention!for your attention!

Documents

Siemens AG Power Transmission Solutions J. Dorn, … · Siemens AG Power Transmission Solutions J. Dorn, ... 115 kV . Substation. ... Further Design Aspects: