How to design a large Solar Photovoltaic Power Plant (1MW & above)

[David Williams]

I can attempt to answer one of your questions:

-> 2. How can you convert the DC power produced by photovoltaic into AC
-> power, as that size large inverter does not exist.

The largest inverters I've seen have been, essentially, large DC motors
driving AC generators. At high powers, this is a tolerably efficient
way of doing the conversion.

Of course, the problems of synchronizing this kind of inverter with the
existing grid are essentially the same as the problems of synchronizing
any other generator. Standard solutions exist.

dow

 

[Eeyore]

I can attempt to answer one of your questions:

-> 2. How can you convert the DC power produced by photovoltaic into AC
-> power, as that size large inverter does not exist.

The largest inverters I've seen have been, essentially, large DC motors
driving AC generators. At high powers, this is a tolerably efficient
way of doing the conversion.

Of course, the problems of synchronizing this kind of inverter with the
existing grid are essentially the same as the problems of synchronizing
any other generator. Standard solutions exist.

Large inverters operating at the gigwatt level do exist.

http://en.wikipedia.org/wiki/Itaipu#Power_transmission
is a good example.

Graham

 

[Mauried]

Large inverters operating at the gigwatt level do exist.

http://en.wikipedia.org/wiki/Itaipu#Power_transmission
is a good example.

Graham

Siemens make hi power DC to AC convertors up to 2.5 GVA.
www.siemens.com
Look in the power transmission section.

 

[You]

Large inverters operating at the gigwatt level do exist.

http://en.wikipedia.org/wiki/Itaipu#Power_transmission
is a good example.

Graham

David (dow) doesn't get out much.......

 

[Mauried]

I see nothing of DC to AC conversion on that site other than a few
hints that it is performed.

Do you have more info on how to find it? Their search engine wasn't
successful for me either.

I would like to see how large power sources are converted.

try this article.
http://www.siemens.com/Daten/siecom...inary/Blackouts_Power-Gen05_Milan_1311979.pdf

 

[You]

I would like to see how large power sources are converted.

easy, get in your "Vehicular for long distance travel" (Car) and
transport yourself to Bonniville, Oregon USA. Take the tour of
the North End Distribution Station. The have pictures of the South
End Ditribution Station, which is the Giggawatt Inverter on the
Bonniville/Clifornia DC Transmission Line. Seeing how you would
be comming from Canada, you will need a Passport to cross the
Border, as well as not being on the Terrorist Watch List......

 

[Mauried]

Article appear to only discuss rectifier stations and filtering
aspects. I don't see any inverter information in that article. If you
read it be sure and take some English articles with you...LOL

It doesnt, it explains it all, however some of the terms may be
unusual.
This article explains it a bit better.

http://www.hvdc.ca/pdf_misc/dcsum.pdf

Note that HVDC stations are called Converters, not Inverters as they
have to convert DC to AC or AC to DC , depending on which way the
power needs to go.
The valve bridges perform both functions.


A normal Inverter, only works in one direction.

 

[Mauried]

Article appear to only discuss rectifier stations and filtering
aspects. I don't see any inverter information in that article. If you
read it be sure and take some English articles with you...LOL

Im unclear then what exactly you need to know.
Article tells me all I need.
If the Terminology is unfamiliar then the following articles may help.




These articles might help explaim what valves are and what a Valve
Bridge is.

http://search.abb.com/library/ABBLi...LanguageCode=en&DocumentPartID=&Action=Launch
http://www.hitachiappliances.com/ICSFiles/afieldfile/2004/06/08/r2001_03_111.pdf

The best solution is to go and have a look inside a HVDC Convertor
Building.

Whats inside a Valve is generally Company Specific and depends on the
power levels being converted, so the general term Valve is usually
used for the Switching elements.

 

[Mauried]

Thanx for the links.

I didn't see any mention of inversion in the first article (previous
post). I didn't realize they were using the same circuits to rectify
and invert. This must present some really bad solutions for filtering
and design. I gues that is what that article was all about. Conversion
only looked like controlleable rectification to me and the English was
so bad, and symbols so strange, I couldn't get though it with any
validity.

Now I wonder where they get these megaVolt controllable thyristors
from. I wonder if they are stacked devices. hmmm.... presents some
protection issues upon failures. I have been responsible for station
protection systems for 34 years now. Nothing this large though.

The filtering is nowhere as bad as it seems.
The reason that 12 pole valve bridges are the most common is that
the strange way the convertor transformers are wired up is so that the
3rd,5th and 7th harmonics get cancelled out , so all you left with is
the higher order harmonics which largely dont get thru the
Transformers anyway.

The valves are made from series strings of either GTO or IGBT
thyristors wired in series.
The term valve is a hangover fro the days when actual valves were used
, back in the 1940s.

Currently present technologies is making 10 KV , 4000 A Thyristors
which are wired in series with usually 16 or 32 devices.
Firing is controlled via fibre optics to get around the voltage
isolation probs.

The stations are so designed so that even with a large failure of
thyristors (very rare.) nothing bad happens.


The largest HVDC line in the world in Brasil has been running now for
20 years shifting 6.3 GW at +/- 600 KV with no major failures.

http://www.abb.com/cawp/gad02181/C1256D71001E0037C1256833006CB3A4.aspx?v=17EA&e=us&m=100A

The cost of the Converters is also coming down rapidly for smaller
power capacities, so that up to around 300 MW the incremental cost
over conventional AC is fairly small.
Originally you needed a line length of over 1000 KM to make DC
worthwhile, but its now down to about 300 KM and 50 KM for undersea
or underground cable.