Author Topic: DIY grid connect Inverter (Read 10021 times)

pemtek · « **on:** June 07, 2006, 10:39:36 PM »

Is anyone interested in starting a design for a homemade grid connect inverter. I have been doing some research and have come up with several theoretical ways of acheiving this with some not so expensive components (when bought on ebay and other places).

For a first prototype I will make an inverter that will synch and backfeed through a 12v transformer at very low powers to keep things safe and simpler and work up from there.

Any questions and useful input would be great.

Thanks

Phil

ibedonc · « **Reply #1 on:** June 07, 2006, 04:46:37 PM »

DIY GRIDTIE will never happen!

they will not alow it

also doing a inverter using 60hz transformers is not the way to do it

pemtek · « **Reply #2 on:** June 07, 2006, 05:05:46 PM »

I wasnt intending on asking permission. I know the regulations for parallel operation here so I can make it comply with them just for my own peace of mind. I will ensure I perform all the tests and the system meets the requirements before I connect anything permanently / unattended.

I know a low frequency transformer is not an efficient way to do it, that is why I only intend my prototype to drive into one so I can simulate the mains safely.

Phil

dinges · « **Reply #3 on:** June 07, 2006, 05:06:05 PM »

I almost fell off my chair...

Don't know what to think of the comment in the title in square brackets. I'm not a native English speaker, you are if you are in Lancashire. What do you mean by that remark in brackets? I hope you mean that the entire idea is a joke, to you too.

DIY grid connected inverters. When you have a working prototype and put the plans up here, I'll gladly download them, print them out and file them. Along with the plans for a homebuilt cruise missile and my 'how to build a nuclear bomb' plans (the ones that, in a footnote, tell you you 'only need to find 15kg Plutonium'.)

Technically anything is doable, even by (well skilled) amateurs. Nothing is technically impossible about DIY grid connected inverters. Whether economic is another thing. The previous poster's remark about it NEVER being allowed will be your main practical problem. If anything should happen to a poor linesman during a blackout...You will be in big trouble.

Peter.

ibedonc · « **Reply #4 on:** June 07, 2006, 05:11:21 PM »

you got it Dinges

the Electronic Co has the say of what connects to their Grid , and if anyone plan on doing it stealth , they will be in big trouble when you kill someone working on the line

pemtek · « **Reply #5 on:** June 07, 2006, 05:16:22 PM »

Point taken.

wdyasq · « **Reply #6 on:** June 07, 2006, 05:54:06 PM »

"You will be in big trouble."

..........but the lineman will be DEAD...

Ron

coldspot · « **Reply #7 on:** June 07, 2006, 07:30:24 PM »

I think it's a great idea-

And even thou it will be very hard to "No way No how"

get it actually conected to the grid.

I'd love to see some plans

I'd put girlfriends cabin and her brothers on it,

No grid up there, and if and when the power lines do come,

I'd be the one saying what and where if they want some of my extra

juice. (That I hope to be able to have WAY EXTRA buy end of season) LOL

I'd like to maybe even set up a mini grid up there for the cabins and

out buildings, (Being that my power station will end up in a tree fort

type of deal when getting closer to done as by only on weekends)lol

Thanks

AnyWay

l8r

kitno455 · « **Reply #8 on:** June 07, 2006, 08:43:25 PM »

i am not saying diy gridtie is a good idea, quite the opposite, it is the quickest way i know of to get a face full of exploding electronics, BUT! no lineman with half a lobe in his head touches even the spool on the truck without his gloves on. "every wire is a live wire" still rings in my head from tele linemans class (shared poles with power co in the area).

allan

Nando · « **Reply #9 on:** June 07, 2006, 09:10:47 PM »

PHIL:

If you are interested, contact me directly, my email address in the heading of the message and change -at- to @ and -dot- to for SPAM .

I can assist you, though not full time, I do have power design experience and know how to do it, though I need to refresh on the regulations.

Many are afraid of such enterprise but it is not very difficult to do -- though not for a KIT building, I think.

Nando

Ungrounded Lightning Rod · « **Reply #10 on:** June 07, 2006, 09:25:30 PM »

Actually, linemen when working on an outage often end up touching (or getting too close to) lines that should be dead and, if the line is live, the lineman can be killed or injured. It has happened, more than once.

Linemen are VERY sensitive to this. If they see lights when they are working on an outage in your area they WILL be by to check. You'd better have zero volts backfeeding the line or you will be in trouble. (You may find yourself being off-grid sooner than you intended, with some extra bills to boot.)

Murder 2 if you fry a lineman.

Void your home fire insurance if you hook up a non-UL-approved grid tie system and later have a fire. (Probably void your liability insurance, too. Pay for the lineman's hospital bills and "pain and suffering" or the widow's settlement out of YOUR pocket. Goodbye house even if you didn't burn it down.)

If you don't want to get UL approval for your design (which is VERY expensive and you have to supply some for them to destroy in testing), the best homebrew grid tie you MIGHT get away with is "pushing on an induction motor" - with care not to have capacitors on your system or on a pole nearby. Then if the grid goes the excitation goes. The motor freewheels and stops pushing back and generating.

ibedonc · « **Reply #11 on:** June 07, 2006, 10:29:28 PM »

Oh , not afraid of it , just stating facts

I have a working off grid design

ps Nando , do not send me the famous "If you are interested, contact me directly, my email address..." troll

JW · « **Reply #12 on:** June 08, 2006, 08:09:48 AM »

Smiles casually, and checks out the rest of the posts.

JW

The Crazy Noob · « **Reply #13 on:** June 08, 2006, 09:31:49 AM »

See my post about a dead cheap grid-tie system that doesn't need fancy electronics and automaticaly shuts down when the mains power dies.

I'm still searching for a strong enough DC motor to test it with a 100W induction motor i have...

The Crazy Noob · « **Reply #14 on:** June 08, 2006, 09:32:24 AM »

sorry, forgot to give the URL

its': http://www.fieldlines.com/story/2006/4/12/165150/484

richhagen · « **Reply #15 on:** June 08, 2006, 10:22:54 AM »

Dangerous and troublesome idea. You don't own the wires, and no utility I know of would ever permit the use of a home made grid tie inverter. If it fails and islands, someone could easily get hurt. You would be better off to design an inverter that would sink up to the grids frequency, and then switch from grid to inverter and back depending upon the availability of power, using either grid power, or your power, but never connecting the two. Generally, you can power your house with renewable energy if you want, but backfeeding the grid involves other peoples property and safety. Rich

Nando · « **Reply #16 on:** June 08, 2006, 11:43:46 AM »

Yes, you may have the old electro mechanical GRID tied system.

In a past message, I indicated the steps for such system -- though I did not specifically identify them -- do you see the reason why I did not ?.

There are ways to do it directly with an induction motor driven by a wind mill -- with much higher efficiencies .

We have used/installed several types for about 15 years with its efficiency limitations.

What did you think that I was trying to do or say to you, that you responded with a stick on your shoulder ?.

Your behavior may be your worst enemy !!

Nando

pemtek · « **Reply #17 on:** June 08, 2006, 12:35:10 PM »

Hi Everyone,

thank you for the comments made I wasnt expecting to be machine gunned down to suggest such an idea but I do see your points. However a number of people are still interested in this subject and therefore is a worthy discussion.

I already know about all the backfeeding problems, islanding etc. One of my good friends is also a linesman and he has shown me how they ground every cable to ensure no islanding can occur.

I do understand that giving anything more than a basic diagram to the average electronic DIYer could be a very dangerous thing to do.

I have a diesel generator with a 7.5kw induction motor with the famous C-2C wiring method already capable of grid connecting and have done several times for short time experiments and it works fantastically. But I want to use free, smell free wind power not vegetable oil!

I also have a single phase 240v 60kva stamford generator which I can use for my own OFF GRID / grid connection experiments when I get my electronics up and running.

I also have a 500w and a 1000w wind turbine both feeding a 48v bank of fork truck batteries. Hence the desire to feed in with my incoming supply to supplement my house loads instead of using a few ton of cells and an impractical inverter.

The approach I was going to take with the paralleling inverter was to have the control electronics fed via a transformer from the mains side of the breaker (APPROVED). The breaker would be powered from this transformer (through the circuitry) so IF the mains dropped or DC was present then the breaker would drop out. The inverter could only supply power as and when it detected EACH 0 crossing events on the incoming line AND if the voltage on the incoming line was in tolerance AND if the timing of the zero crossing events were in specification.

IF all of these requirements are not met then power will not be supplied to the DC contact breaker or the dc-dc converter or the h-bridge or the mains contact breaker. In the event of any of the requirements not being met the system would disconnect and not retry connection for a preset amount of time.

Please no more warnings and information about killing linesmen law suits and legal requirements unless they are about the circuit or the protection methods.

Thank you

Phil

> Awaiting the next depth charge of warnings :-D

Nando · « **Reply #18 on:** June 08, 2006, 01:30:54 PM »

Depth charge NOT FROM ME !!

Death warnings come mostly from those that have limited electronic design experience and fill the ncessity of presenting a warning at all costs !!

Certification is required if the product is going to be connected legally and or produced for sale in the world market.m

This is the reason why some systems already in some places are not sold but connected like "GUERRILLA WARFARE" -

The idea is doable and the way you are directing the testing via a small transformer is exactly how the design should be approached.

Make sure to add a fast and sensitive current detector with good controlling parameters to insure proper protection, also, initially add a resistor in series for additional initial limitations.

My question is: what is your experience in power electronic circuit design ?

Nando

Bruce S · « **Reply #19 on:** June 08, 2006, 05:07:07 PM »

Phil;

I cannot give you info on this idea, but will say that from the amount of time I've spent reading emails and reading the depth of nando's knowledge , I'd say send him a private email and not worry about the nay-sayers.

Sure if someone were attempting this I'm sure nando would be one of the 1st to shoot him down. But there was enough info in your current post to show that you have the experience and knowledge to tackle this.

To Thos who shoot these things down right-off, don't be so quick to judge. There are those on this board that do in fact have the knowledge to do this. Whether it's cost effective isn't the main crux of this.

If that was the case I'd never have gotten into building winds mills or RE ( except of course the Alky in my truck).

Phil>>

GO FOR IT!! you have my support

Bruce S

PS>> The current "approved" Grid tie units started out as DIY and not UL approved.

pemtek · « **Reply #20 on:** June 08, 2006, 05:25:38 PM »

Thankyou

from what I can gather there is only 1 grid tie inverter that conforms with the required standard in the UK although I know several types are used in various CHP, wind and solar installs around the country.

From what I can see some of the type tests they perform are quite limited and dont even seem to go into reliability tests of the circuits!

Phil

powerbuoy · « **Reply #21 on:** June 08, 2006, 07:49:48 PM »

I do not see anything wrong with his idea. Why should a gifted electronics guy not try to come up with a gried tie inverter? How did Xantrex, SMA or all the others start? Some guy in a garage with smarts ...

Lets assume some people here get together and built a working unit, next make sure that the unit has the necessary over/under voltage -frequency recognition card, contact UL, tell them that you have ten prototypes for them to burn up, get it listed under UL1741, go thru the tests, loose some cash ... tens of thousands plus quarterly follow up visits ($350.00 a pop) and start selling. Would be nice to see the prices come down, inverters are still way to expensive. If they would come up with a unit and sell it for dirt cheap instead of raking in extreme profits and therefore stalling the renewables progress, then I would be more than happy to throw in my five bucks for the testing. If everybody on the board would do the same, UL expenses would not be a problem.

Powerbuoy

craig110 · « **Reply #22 on:** June 08, 2006, 08:03:16 PM »

Absolutely agreed: There is no reason why a "gifted electronics guy" couldn't come up with a good design and start a company to market it as a cheaper tested product. Sad to say, that isn't what this thread is talking about, however, when phrases like "I wasnt intending on asking permission" and "DIY grid connect Inverter" are being used.

TomW · « **Reply #23 on:** June 08, 2006, 08:17:10 PM »

graig;

You hit the nail right on the hammer.

I guess I don't have the vision required to tell from a few words on a message board that someone is a "gifted electronics guy" [or gal] altho sometimes a few words can clearly indicate a moron. Not saying it applies here.

Just an opinion and offtopic kind of maybe.

T.

scottsAI · « **Reply #24 on:** June 09, 2006, 12:48:36 AM »

Have any of you thought about this Islanding problem, that runs rampant on the power lines?

A lineman brother-in-law in over 20 years has never seen a DIY back feed for a very simple reason.

When the power grid goes down, it's impedance as seen by your house "back feeding" the grid goes to ZERO. The back feeding generator would have to power the entire grid. I have not seen anybody with a generator that could attempt this without exploding. Great things called breakers prevent this. Yes, when power fails the local power stations breakers may be open, that still leaves everybody on your line to power to create this island.

Lets say you some how create an Island... this island can only be as big as the load your generator can output. Lets see about a house or two? So, how do we get just the right size island?

I have looked on the web for a bonafided case of a lineman dying from a DIY back feed, do you know how many I found? None.

Second point, how many people do you know that would even try? Based on comments not many. I know more than 200 engineers, maybe besides myself one or two might even think let alone try.

After all this is considered, I question if the lineman death ever occurred.

As already stated:

PS>> The current "approved" Grid tie units started out as DIY and not UL approved.

After the first couple post here it became very redundant.

Where has DIY gone?

pemtek · « **Reply #25 on:** June 09, 2006, 12:56:31 AM »

I will admit that my early post was a quickly thrown together badly thought about post, driven by being written quickly late at night. Immediately I got replies from it I realised that I should have turned on a few more brain cells before posting!

Anyway Powerbuoy has the right idea. Even if this exercise could spark a company into building a grid tie inverter. Maybe from circuits put together here, for reasonable money, then it will have been worth it.

I used to work for a test house that specialised in Electrical testing and EMC. Alot of the work was for the American market hence was UL testing. One of my good friends is the manager there so guidance with UL approvals would be no problem, especially since he has a solar setup himself and is very interested in renewables.

Phil

Infinity Steel · « **Reply #26 on:** June 09, 2006, 07:01:07 AM »

My take on this comes striaght back to legality. You cannot connect hardware that is not approved to a utility net-period. If you get caught doing this without permission-you face legal consequences.

Ergo-this entire discussion is moot. DIY devices will not be approved and are ILLEGAL-end of discussion-waste of time and money.

dinges · « **Reply #27 on:** June 09, 2006, 07:35:16 AM »

I fully agree with you. Had the urge to mention the illegality of it once again, but the original poster seems to have made his mind up. Even if he is very capable with electronics. If he is, I don't think this is the right group for this kind of questions anyway. Sci.electronics.design or something like that would give him much better answers, I think.

Not all the rules are there just to tease the people.

But: "You cannot connect hardware that's not approved..."

What's the legal details here? I'm a HAM and in The Netherlands, I can build anything I want and connect it to the grid to DRAW power. Backfeeding from a DIY inverter would be off-limits though, definitely not legal.

But, in USA, I assume it's legal too to draw current from the grid by homebuilt devices? Or does ANYTHING that connects to the grid need to be approved?

Peter.

Bruce S · « **Reply #28 on:** June 09, 2006, 08:25:39 AM »

Not wanting to start an arguement here on such a beautiful Friday morning; so I'll merely state that I disagree on your points of DIY devices not getting approved .

There are very straight forward rules within the UL, CSA, CE & TUV for getting such devices approved.

We have gone through all 4 with medical devices that have class 3 and class 1 power-supplies. One must only follow the guide lines set forth by them to get these approvals that's all.

As the whether it's a waste of time and money or not, that is a a decision left to the builder.

What price can be put on knowledge gained?

I for one am glad the current grid-tie invertors that are already approved, didn't take the idea of not worth the time/effort. This is why the are indeed costly, it is a supply/demand issue at this time.

Since these are my opinons I'll end by merely agreeing to dis-agree.

Cheers

Bruce S

John II · « **Reply #29 on:** June 09, 2006, 07:57:18 PM »

Here's my 2 cents on the idea.... and because copper prices have went up a lot.. I'm offering a lot of ideas for just 2 pennies... lol

Here's the grid tie inverter I'd like to see developed.

( 1 ) It would never back feed the grid, and be designed so that it can not do so.

( 2 ) It would allow you to use all of your homemade power, and any second or minute there was a power deficiency concerning all of your loads... it would use the grid to fill the void.

( 3 ) It would not use huge banks of batteries to accomplish this.

Note: There should be no U.L. or other high dollar approval for such a device, because it does not back feed the grid. How many of you build an item that connects to the grid such as a DC Power supply without the need for U.L. or other labeling ? This device would be no different.

Some draw backs and advantages to such an grid tie system.

(A) There will often be times when your home system is producing power, but you are not using it. Because it's neither feeding the grid or charging batteries, unless you have an alternative dump load, you'll often be throwing away valuable home made power.

(B) In States that do not allow `net metering' and with utility companies that are willing to put you though tons of unnecessary paper work to connect a standard grid tie system.... The inverter as described above would be a welcomed site to those that do not want to mess with truck load sized battery banks.

Technically it is possible to build this thing. But who will and who can ? That be the question : )

John II

craig110 · « **Reply #30 on:** June 09, 2006, 08:20:58 PM »

Hi John II,

When I was determining which GTI to get, I spent quite a bit of time reading the Outback Power Systems user forum (http://www.outbackpower.com/forum/index.php) and recall someone asking about exactly the configuration you described. I just went looking and can't find it, but if I recall correctly the answer in the forum was along the lines that they are working on it.

Craig

srnoth · « **Reply #31 on:** June 09, 2006, 10:00:46 PM »

Hey scottsAI,

I aggree with what you said there. I think it is highly unlikely that an experimental grid tie inverter will have enough capacity to power an entire neighbour hood, so for this sake of this discussion, I aggree with you. But.

The question of backfeeding is one that most definately needs to be considered. I'll give two expamples why:

I live sorta in the forest, with only six houses nearby besides mine. We are all fed from one 50KW transformer, and when the fuse blows on that it is only us six that go down. So, now a hypothetical situation:

It is day time, everyone but me is at work, so in the other houses the only things on are a few friges, a computer or two, maybe a few lights. Max load there would probably be 10KW including my house, probably less than that. Now, smart me decides to connect my (hypothetical ;-)) 12KW deisel genny to my breaker panel, so I can power my whole house. But, I forget to trip the breaker going to the grid, and voila, my small island of 7 houses now has power. If a linesman touches those lines, it will hurt. Probably not kill, since it is only 120 or 240 volts, but still most certainly has the possibility to be deadly. Now I'd have to be a pretty big idiot to do this, but there are people who might. Also, lets say I build a genny from a huge induction motor and fed that straight to the grid to sell back current. If I put capacators on it, it will continue to generate power even when the grid dies. So, again, possibility of a dead linesman.

Now, my second situation is completely true (if you can believe the newspapers, that is, lol!). There is a sort of club/dancehall type place where people have wedding and parties in a remote costal location in my country called Pier 1. It is quite a large place, so their backup generator is probably around 20KW. One day, the power company had turned off electricity in their area to service the lines, so Pier 1's genny was on. But, due to bad installation, etc, it was feeding power to the lines, and the linesman who was servicing them was killed. Yup, killed. Dunno what happened as a result of this, like lawsuites etc, but the fact still remains that a guy DIED. That should be reason enough to be VERY CAREFUll with this sorta thing.

So, I say go to it with your small transformer design, if you know what you're doing. A small transformer with not be able to power even your whole house, let alone your grid, so there is no real danger there. Once you get to larger models though, you should make your own 'mini-grid' to test it with, by using a backup genny or something.

Hope you do well, it is nice to see somebody who feels very strongly about doing this, and is not shot down by other people's negative comments. Keep safe, don't kill yourself or anyone else. And have fun.

Cheers,

Stephen.

pemtek · « **Reply #32 on:** June 10, 2006, 04:26:36 AM »

It is quite possible to design an inverter to synch with the mains and not back feed under any circumstances but theoretically it would need all the safety devices of a standard grid connect inverter. The reason being as with one simple fault/measurement error it could backfeed.

Id love to be grid connected with my turbines right now, between them they are pushing over their rated output of 1500w and 3/4 of it will be going to waste as its only powering a computer!

News:

Author Topic: DIY grid connect Inverter (Read 10021 times)