Main Grid Assisted UPS Inverter Micro Controller (Solar and Wind Turbine) (Arduino)

Refeek Maher

The Title of this is just buzzwords that are involved in this project.

I'm looking into a system that offers an AC uninterrupted power supply as an output.

It's main input will be from both a wind turbine and a few solar panel (There also could be a generator involved yet). I'm thinking about a 2 kW wind turbine and 1 kW from solar. Both go through a charge controller to feed batteries or to a dump when the batteries are fully charged.

Usually batteries would then be connected to a DC to AC inverter. However, there isn't a guarantee that there will be a constant supply of electricity to the inverter seeing as though solar only provides energy for daylight hours and the wind turbine will only supply when there is wind. The batteries would keep the inverter going for a while but would go dead pretty quick if there was a requirement of up to 2 kW!

I'm thinking the solution for this would be to have a grid assisted UPS. A system that would switch over to mains supply when the batteries began to drain of there energy.

I have googled the living daylights out of such a system but haven't found much on it. Only grid tie systems and systems that have no grid assistance.

Basically, there needs to be some sort of micro controller (Arduino or raspberry PI maybe)
that can activate a relay possibly to switch to mains(???) Although then there is the problem of that split second when the coil in the relay switches over causing a short period of no power being provided. Perhaps a basic UPS that is used with computers could deal with that sudden dip? (generation>charge controller>batteries>Inverter>(relay with option of grid mains controlled by micro-controller)>UPS> computer, monitor, laptops etc.

Is there an inverter out there that I haven't found that already incorporates the above?

Any arduino or raspberry PI enthusiast that have come across a similar project?

Has anyone anything to add to this or have any experience with something similar to this?

Any information shared on this would be greatly appreciated!!

Chet T16

http://www.chet.ie/?p=107

I wouldn't chance pulling 2kW through it though

Refeek Maher

That's exactly the kind of thing I'm looking, actually that's really cool! Is it something you were involved in?

Well 2 kW was just a rough number I through in.... It will probably end up being a lot more.

It's looking like i'll be getting three 2.7 kW UPS systems this weekend!

BrianDug

I do not have anything helpful to add but I just wanted to say it sounds like a really interesting project - I would like to know how you get in with it.

Edit: RE Arduino or Raspberry Pi - I own both, they could both do the same job more or less but I'd always use the Arduino if I am looking to build something small and quickly - could be just a personal preference. Arduino has the ability of DPM (Direct Port Manipulation) so the commands can be executed very quickly. When you write the code using the built in commands such as DigitalWrite(x,x) it is actually a few lines of code under the hood that has to be processed over a few clock cycles so it can slow things down in high speed switching applications. Hence DPM can achieve faster command execution.

I don't now if Raspberry Pi can do this so its worth looking it up.

Also why not build your own inverter?

Refeek Maher

BrianDug - Thanks for that! Ya definitely, I'll update this post every time something new is added!

Well maybe then a combination of both raspberry PI and Arduino would be best? This also has to have remote access so that it can be somewhat way managed when I'm not there. Any ideas on that? I'm thinking I could access the raspberry PI using SSH client Putty which then would be connected to the arduino .... Although there could be a lot better solutions out there than that...

An Arduino so would probably be best... and it has more pins for use with relays, sensors etc..


I've never thought of building my own inverter to be honest... that would be a cool project though! Have you done this before?

BrianDug

Yeah you could use SSH on the Pi. I have a mini wireless dongle for mine, a wired connection would be better as wireless can be temperamental at times I found.

For the Arduino you can buy "shields" and addons such as a GSM module that contains a SIM card so you can do a host of things. Checkout XBee for arduino also.

I have not built an inverter before but I am in the process of building one at the moment. I am going to use an Arduino to switch my IGBT's. I was looking into DPM recently so will probably go down that road.

There is very strict guidelines on grid tied inverters. You have to be very careful not to back feed into the network. So in a grid tied system, should the mains voltage go down your inverter is required to disconnect itself if my memory serves me correct. There is a document for Ireland that covers all the requirements by ESB called " Conditions Governing the Connection and Operation of Micro-generation"

See a similar thread for additional details:
http://www.boards.ie/vbulletin/showthread.php?p=66923074

Refeek Maher

I have often found as well that wireless can be dodgy with Pi's... I have xbmc on one and it's more temperamental than the weather! Some images can also have complicated set-ups.

That's definitely something I have to look into! XBee looks amazing!!! Have you used it before??

What exactly is DPM? What kind of power will your inverter be able to handle?

I have done my research on that and your right, there is approved grid tie inverters out there that turn off when the power is switched off to prevent someone down the line from getting electrocuted... However, I am not using a grid tie inverter. I am hoping to only use mains ESB electricity only when I have no electricity generated myself (Grid assisted). See the link below for the type of inverter that I am talking about. I've found it very hard to find these types of inverters online!

(samlexamerica.com/products/ProductDetail.aspx?pid=101) I had to take out the "http www." because I am a new user and cannot post links

As for grid tie inverters, is it still possible to export electricity to the grid??

Refeek Maher

tinkerforge.com/en/doc/Kits/ServerRoomMonitoring/UploadSensorDataToXively.html

Has anyone experience with this? looks really cool!

BrianDug

I have never used the XBee before unfortunately.

My inverter will be about 300W, although I can easily ramp this up and the components I am using are capable of handling a lot more than 300W of power.

The grid tied inverter idea is quiet a technical area so it requires a lot of reading to find answers to your questions. I could not give you a definitive answer without having to look into it myself.

DPM - Direct Port Manipulation: If you are using the inbuilt commands of an Arduino and execute the command say DigitalWrite(X,X), this will be translated to machine code and executed over a number of cycles (time) and all takes place behind the scenes. Using DPM you can perform the same commands but they are coded differently. They can be executed much quicker by the processor.

These savings in time can be vital in high speed switching applications as you need to ensure there is sufficient dead time between switching and that your switching scheme is been executed correctly for the period you have programmed. (That info might not make sense if you are not familiar with the inner workings of an inverter)