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Topic: Wind turbine charge controller prototype/shield (Read 9 times) previous topic - next topic

mgshightech

@rockwallaby ... some of our other guys are working on a scada system. But they have been a little slow. I found a pre-written php web based scada system.. actually there are a couple of them that I found.  But one of them is pretty much written up in french, which loses me.  It is our intention to do the same kind of scada work you are talking about as another component of the project.   :-) 

rockwallaby

#31
Jan 02, 2013, 04:42 am Last Edit: Jan 02, 2013, 05:00 am by rockwallaby Reason: 1
Hi mgshightech,

That sounds interesting, about what you say regarding SCADA systems.
I have worked with industrial SCADA systems for many years, programming them to work with industrial PLC's.

Funny you mention that it is written up in French, as I am just on a French website checking out some things to do with motorcycling for when I head back there in June this year for some months. You could use something like Google translate to help maybe?

What I have been working on over the past months is something that appears like a SCADA system, but to work with small micro-controllers like Arduino's.
There is still much for me to do in regards to developing it to how I intend, and yes, progress has been slow for me as well.

There are two basic approaches I have used;
One is where the Arduino is the server, serving up data to the client, I do this using json formatted data. It is nice and efficient.
Second is where I have the Arduino push up data in json format to my SQL database on my hosted site. Then the host server simply pulls data out of the SQL database and gives it to the client when requested.

The second approach is where I am moving toward as it allows for better through put of data if there are many clients connected.
The Wiznet ethernet for Arduino can only support four simultaneous connections according to the data-sheet.
By having the Arduino push data up to a hosted site gets around this problem and allows for many other possibilities.

The Arduino essentially is the component which gathers sensor data and provides any needed output control, such as PID loop controllers and so forth.
The client side (browser) is mostly made up in javascript and I currently use Backbone.js as my framework to keep things as neat as possible.

Another active member on this forum, Graynomad, is developing a very nice piece of hardware and the software to go with it that might also interest you.
It is called ArdweeNet and it is designed with networking in mind, using RS-485. What Rob is developing I believe slots quite nicely into this area of control.
Maybe Rob might come in at some point if he is interested to do so.

I would be interested to learn more about what you have found in terms of that php based SCADA system if you get a chance.

Regards,
Paul

PeterH


He asked why a wind turbine requires mppt while a solar panel doesn't. The answer is this.


The Wikipedia article about MPPT is wrong, then? You ought to correct that.
I only provide help via the forum - please do not contact me for private consultancy.

mgshightech

I wouldn't be so bold as to assert that the wikipedia article is wrong.  It is only in special cases that other methods are just as good. If you are aware of the special cases, you can take advantage of them to your benefit. If you are unaware, then mppt away.

sorry I haven't been around .... flu ... I have been quite miserable and am still sick.

@rockwallaby ... I thought I named those packages for you. Somehow I don't see th post here, so I am going to repost them. (at least it seems that way to me) the package names are stantor (french)  and seer_2 or s.e.e.r. 2  (english) both available on sourceforge. I would try the seer2 package first.  Just look them up on sourceforge.  I'll be back around as soon as my body is ready for it.






mgshightech

look here:   http://www.wholesalesolar.com/products.folder/module-folder/Eopply/EP125M72-190.html 

you will see that the these curves show that the maximum power voltage doesn't change much as the sunshine level drops.  The wikipedia article shows curves with a more dramatic alteration, but all the curves I have seen for market panels look like this.  (above) So, what you do is you figure you're going to lose a volt IR in transmission, and that if your remaining (max power point) voltage at max sun is around 6-8% too high for the battery, you will not  lose much power because that is within the range where you will only lose around 3% of your power. You'll lose that much power by forcing it through a transistor.  So, then your panels output voltage can drop as much as 12-14% and you will still be within range to only lose 3% of your power. The stats of panels show that the output voltage won't drop more than that.  There are things helping you by the way. When it gets cold and your panels output more voltage, your batteries require more because their internal resistance rises. When it gets hot and your panels output less, your battery requires less. When your panels output current drops and the voltage drops a little as well, guess what, the battery doesn't ask as much voltage because it's internal resistance is causing a smaller IR drop because of the smaller current.  .. So we are going to do tests to verify this stuff, so stick around if you are waiting for the test results.

So if you pick just the right voltage of panels for your condition, you can happily charge with relays and get as much as any other method.  Unfortunately, only maybe 20% of panels lie in the proper voltage range. The rest are going to require fussing.  There are multiple things that drag you out of this ideal zone.  If you are covering more distance, you may consider using  relay charging with 18/35/70 volt panels to offset the IR loss of the cable, or, you can go high voltage/mppt.  Relay charging with 19/37/72 volt panels would only make sense if you were charging a long ways away from your panels, and for panels in the low voltage range like 14/28/56 volts... well, if you want them to reliably approximate maximum power, you are going to have to series/overvolt and mppt.  Consider the 14 volt panel you lose a volt in IR losses, now you're at 13, and you can only trickle charge. If you put a blocking diode in there, you are dead. In my opinion, forget the blocking diodes, just have your controller turn the panels off at night.  Relays suck power for their coils, but only 1-2 watts for 60-120 amps of current capability. That is a lot less than losses in 60 amps of blocking diode. (like 20-30 watts)

Also, I don't think mppt controllers are generally designed to boost ... assume they can only buck and supply them with extra voltage.

I'm going to try and use relay charging. We'll place the panels close to the charging station and use 2 guage cable.  I have an mppt controller, so I'm going to make a comparison and cough up real data. 

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