250 watt grid tie inverter build

blueroomelectronics said:

I wonder how much you actually get per kWh when you sell power back to the power company. After all when you buy it you also have to pay taxes & delivery charges.

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after you have paid for all the equipment particularly their meter to measure what you put back you get the grand sum of 30-50% of what you buy it at if your lucky so unless your house is made of PV panels with giant turbines on each corner, the patio paved with PV tiles and all fence/gate posts replace by turbines you won't make much money from it, I would think that with what it costs to set up you could buy a nice bank of batteries capable of storing 5-10 KW making you indipendant anyhow

tcmtech said:

What I have been told as of lately is that my local power comany pays equal cost per KWh returned. BUT I have also been told that may not be true all over the united states.

Right now I pay around 9 cents per KWh. Plus a fixed $29 month conection service fee. IF I were to sell back to them I would get 9 cents per KWh or I could just bank my retuned KWh's and reuse them later at no aditional cost. My local utility is pushing very hard to encourage its customers to invest in alternative enegry and energy saving devices.

But not all power utilities are like that as I undrstand it.
I have heard that now that its legal nationwide to sell back they do have to buy it from you. BUT they only have to pay you the going rate of what they pay for it at super bulk rate. Which as I have understood can be anywhere from 1.5 cents per KWh to around 5 cents per KWh depending on the location and demand in the country.

Plus If they want to they can require you to have a second meter on your service connection to read what is going back and then charge you for that second meter.

SO if your getting 1.5 cents and spending $30 amonth for a second meter on top of the $30 a month you pay for the first meter you would have to make around 4000 KWh returned just to break even.
And you still have to make what you normaly use too!

But if you are lucky and have ulility company like what I have then you only need to make enough at 9 cents per KWh to pay for the one meter that runs both ways. Or about 334 KWh returned to break even.

In the first example I would have to make about 5500 KWh a month to break even including my own monthy use.
However in the second example I only need to make 1834 KWh a month to break even.

And my numbers may be off a bit on actual meter costs and utility bulk rates. I just used the numbers I have been seeing in articals I have read.
And the rules are changing all the time so this may not be exactly acurate in every detail.

I dont know what Canada is like for any of this though.
But its worth checking out!

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and your the one designing powerful grid tye inverters ? I think you just killed the use of anything more than a 250 W GTI,

me I'll be happy keeping my solar system off the grid and running my PC monitor for as long as it lasts before going back to the grid and waiting for the next day for more power....

A grid tie inverter is a cost avoidance device not a money maker at the home use scale.
Every KWh made by you is one you did not have to buy from the utility.

Several posters and I covered this in the Grid tie inverter schematic thread.

Are you just not reading or are you simply posting to take up and waste alot of space on these threads.

Thunderchild If you dont agree with what we are working on just shut the F up for a while! Are you happy now?

I hope Nigel or one of the other forum moderators takes agood look at your posts so far. If I was him I would start dumping some of them and the replys related to them just do to pointless repetition and being a total waste of readers time!

Nigel or any other moderator would you kindly read over this thead when you can and edit it if you feel its needed. Thank you!

Its becoming clear you are either just not reading the relative threads and posts, or not understanding them when you do.
Or your most likey just spamming to waste everyones time!

I am trying to be helpful and give some useful design information out to my fellow forum readers. I do not mind answering questions relating tothe build consepts but so far I have wasted alotof time and thread space on one persons non relivant run around.
So far there is about one page of usefull information and two pages of just Thunderchilds mouthing off and the replies to it

There two ways to make some thing one do it and two talk about it. Now I think tcmtech
Is doing it. He has posted some good points. So let's not take a way from this by being one to just talk about it. Let's get are parts out put heads together and try to make a good Grid tie inverter.

Plans and Parts Lists

I too am following this with great interest. I have a wind generator working a commercially purchased 250W grid tie inverter. I'd like to expand my capacity, so your work is an excellent find for me. Unfortunately, I probably am one of those idiots with a solder gun you refer to, although I work am not an ex hippie an try to restrain my nutcase enthusiasm for alternative energy.

1. Am I right that a parts list is not necessary? One gets by from any brand or generic part that meets the stated specs? Correct?

2. Will your units work in series to increase capacity? I'd like to get to 2000W, one unit at a time.

Thanks for your contribution. The cost of commercial units is not practical. Here in Alaska, we have to do it ourselves at a certain point.

John

Yep!
I was just pokeing some fun at the few nuts that tend to get carried away with their views on alternative energy and the related life styles, along with those few that really just dont have any idea what they are doing when it comes to electronics and circuit fabrication.

I am pushing hard to have myself on 100% alternative energy power within the next year. However I am not going tribal to do it. I want to keep my energy wasteful ways I just dont want to pay for them!

The intention of my giving general specs is just for that reason. Anyone good at scrounging should be able come up with parts dirt cheap! If they cant find used items they will still have a general idea of what specs and values to be looking for when they have to buy them.

As far as using multiple units for higher wattage these should be able to run parallel with out any problems that I am aware of. (within reason and if built properly)

If you need a higher input voltage or current just change the peak limit values of the semiconductor devices to make up for the difference. Plus, make sure that the control circuit voltage divider resistors make up for the voltage change and your power transformer is capable of running at what wattage you are going for along with changing the power factor correction capacitor value to match the different size transformer also.

I will try to get around to doing more posts relating to the build as soon as I can.
I had some work come my way this last few days so I have not been able to get time to work on this thread.

Sorry for the delay!

Hey TCM,

Just happened to come across your posts - kudos! I'm still waiting for my SWEA to arrive so I can tear it down, but from the few pics I saw it looks like SWEA used the same old same old: Push pull to make an HV intermediate rail and then 4-quadrant PWM.

Anyway, I see that the converters you are discussing here mostly lean towards a 60Hz transformer. Very durable, but a little heavy. Would you be interested in collaborating on a direct-drive topology? ie - buck right to the output at 20-50kHz to reduce that 10lb 60Hz transformer down to a 6-oz toroid inductor?

Anyway, let me know if you are interested - maybe we could split the direct-drive GTI into another thread or something. Two heads are better than one! And BTW, I design DC-DC IC's, so I have actually heard of those mosfet things you've been talking about.

tcmtech said:

I am pushing hard to have myself on 100% alternative energy power within the next year. However I am not going tribal to do it. I want to keep my energy wasteful ways I just dont want to pay for them!

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if you can save energy then you will go indipendant faster and with less expence. to say you want to keep your wasteful ways but not pay for them dosen't make entirely sense because most renewable form will take quite a while to pay themselves back so you will be shelling out more money to make enough power to waste

Paying out of your pocket book and paying with hard work are two very different things =)

Definitely!
I would be happpy to do a bigger more complex GTI build with you.
Then you could teach me a few things too! I tend to stay away from what you are talking about. I dont have much hands on experiance with it.
I dont care for theoretical design myself. I have often found that it fails or falls short when its actualy applied to real life conditions. If I have not built it and tested it myself I tend to not get to excited about it.

However being you do have some knowlege in that area I will still help in any way I can.

So far I have been sticking to the 50-60 hz transformer design just because they are very common and easy to work with. If I keep it simple far more people will be willing to try and build one.
This design is intended so that an average person can build one in a day with common and cheap yet reliable parts.
I am strongly leaning towards simplicity, duribility and cost effectivness for this build.

Being I have piles of scrap and scrounged items this 250 watt GTI is a zero dollar build for me. I have all the components, I just need to put them together. You cant beat that cost wise!

Plus it gives a very solid base understanding of how this type of device works.
And for me that is the whole point. I could easily overcomplicate this to the degree that maybe 1 in 20 readers could possibly be able to build, but what point would that serve.

And for actual running efficiency a well built one of this design will run around 80 -85% efficient under most working conditions.
If a complicated unit runs at 90-95% efficiency but costs 4 times the price to make and takes 5 times longer to build, plus is naturaly more prone to break down, I dont feel that a person will have gained anything.

These GTI systems are not money makers for the owners. They are cost avoidance devices. Every KWh a person make themself is one they did not have to buy.

IF a person builds one for $50, then it does not take that long to get a cost avoidance equivilant payback on it.
But if it cost $500 to build and tends to break down before its cost avoidance payback is recovered what good does it really do? Even if it was 10% more efficient.

And as far as I have ever seen simple, rugged, and reliable lasts! Complicated, dellicate, and fussy does not. I will trade efficiencey for simplicity and durability any day!
And for me how heavy it is does not matter. As far as I know once its hooked up you should not need to be moving it.

if you can save energy then you will go indipendant faster and with less expence. to say you want to keep your wasteful ways but not pay for them dosen't make entirely sense because most renewable form will take quite a while to pay themselves back so you will be shelling out more money to make enough power to waste.

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Very true! However I do have an advantage over most others.
I have the knowlege, equipment, materials, and location to build a large enough system to keep up with a large personal energy usage.

Just by the numbers I should be able to produce around 2000 KWh a month from my local winds. But I do have a honest finacial outlay of around $1500 into the parts right now. And I do expect to have another $1500 more spent before I am finished. Plus factoring in generator and system maintenace costs plus my $30 a month utility connection fee, I dont actualy plan to break even on cost avoidance for this venture for about 3 to 4 years.

I do realize a city dweller with solar panels or a small wind generator unit and less personal knowlege of design would not be able to do what I am doing for anywhere near what I have into it.

But thats why I am sharing this knowlege freely. It will inspire some to try, and thats all I can ask and hope for.

Plus this type of system is not going to be able to be used by everyone. Many have local laws and regulations that will force them to use battery banks and inverters to be able to run off alternate power sources.

But for many like me, getting to legaly use the local power grid as a big alternating current battery is a big cost outlay saver.

If I understood your previous posts you need to run off batteries and an inverter for your alternative power, right?
What did that cost to set up? And if equated to cost per KWh produced over its realistic life span what is the actual number you come up with?

I am just curious. Thats all. Actual numbers help others to find out what will be best for there application.
I fully admit what you are using may very well be more cost efective for some people than what I am doing.

And dont forget that for many just as myself this is also a hobby too!
And most hobbies dont make an honest fincial profit or return. They get measured by fun, learning, and stress reduction, not by dollars and cents!

tcmtech said:

But for many like me, getting to legaly use the local power grid as a big alternating current battery is a big cost outlay saver.

If I understood your previous posts you need to run off batteries and an inverter for your alternative power, right?
What did that cost to set up? And if equated to cost per KWh produced over its realistic life span what is the actual number you come up with?

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yes being grid tied is a huge cost saver as it eliminates batteries and the lost efficiency of charging/discharging that battery. At present I have my old car battery and 40 W of solar panel so I'm quite small scale (cheapo 150 W inverter), the battery is sort of free as it off my old car. however if i wnted to expand I'll be spending a fair but on batteries, the particular set i would like are £ 500 thats the same cost of about 8 20 W solar panels so its quite a burden. I'm not particularly in it for the meney saving either. I just wanted to give it a go and get the hand on experience, infact I have spent more than anticipated after buying tools and other miscelaneous materials and giving a chap a fiva for borrowing his ladder. of course I am also reducing my carbon foot print by a negligeable amount.

in the UK being grid tied costs more than its worth unless you seriously have a house made of PV panels and the patio tiled with PV tile plaus some windmills

Since your system is still inthe growing stage this may be some usefull information for you. Maybe.

If you dont mind using fair but used solar panels you may possibly be able to get them cheap by checking with your local highway and street maintenace departments.
Around here it has become standard issue to use the solar powered portable street signs. Those sign carts do get tipped over by wind and dumb drivers fairly often.
When the solar panel glass gets cracked even just a little they replace the whole panel. An associate of mine said he and his neighbor checked in with their local solar sign maintence company and were able to get a pickup load of cracked solar panels for hauling them away!
He did say some were beyond repair but most had large enough sections that they were able to do a little repair work and make a few complete units out of several broken ones.
He said that they spent a good weekend with a glass cutter and were able to rework many of the bigger panel units and got good useable power out of them again. And the price was right!

I dont know what you guys have around your area for portable solar powered street work signs but it could get you a bigger setup for cheap!

Just something to think about!

I am not a solar panel person so do not know exactly what is involved in reworking one though.

not sure we have that sort of thing around here. there is the odd fixed flashing signal that has a solar panel and tiny wind turbine but as they never move they don't get brocken and are far and few between anyhow. my main issue is the battery cost, as the battery's serve little purpose overall but are needed to temporarily store the power

tcmtech said:

Definitely!
I would be happpy to do a bigger more complex GTI build with you.

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Awesome! Give me a few days to finalize some work stuff and I will ping you with my first thoughts on the topology. Then, we can decide to start a thread for that device, or just to take it off-line until it becomes a little more concrete.

H Bridges

I hate to show how green I am to this, but I find all the components readily available except the H Bridges. I guess I don't know the correct search descriptors or likely places to scrounge these.

Look for bipolar stepper drivers, those are usually dual H-bridges.
I've had the same trouble finding h-bridges on Digikey searching for h-bridge or it's variants

The H-bridge is actually made of 4 mosfets, say IRF540. But now you need a way to drive them. You can either buy an off-the-shelf H-bridge driver or build one up yourself out of discrete npn/pnp's.

One good source is to look up the schematics for UPS converters (of which there are many on the web) and look at how they drive their H-bridges.

Here's another resource for you:
H-Bridge Electronic Circuits

The H-bridge is just a configuration term. It can be a four single devices or any combination of devices. A half bridge is a pair of devices configured in series. Two of them make a whole H-Bridge.

Here is three examples of what they look like in actual schematical and in real life terms.
These are just for reference. However you can buy these or ones like them on surplus electronics sites and eBay rather cheap.
(However you probably dont nees 600 amp 1200V units though!)

Control system Component Function Basics I.


This GTI build up Thread is intended for residants of the united states only! Should you decide to build and use such a device as this you may be breaking laws and can face possible fines, and or jail and prison time for it. Should you chose to build such a device as this and intend to use it for saving energy in your home or dwelling you are still breaking the law. Beware you are considerd a pirate Grid tie operation, which is considered illegal in many countries!

For the control system to work properly you will need to be able to monitor several different AC line signals and the simplest way to do it is with a good old fashion voltage comparators. These circuits may seem a bit crude and simple but have proven that when built right they are reliable and efficient for the purpose.

HIGH – LOW WINDOW COMPARITOR

This circuit uses two comparators set up the same as the dead band window comparator circuit but instead it monitors a voltage signal and the output only goes high if the signal is between the minimum and maximum limits.

If the input signal is below the minimum input reverence voltage X1 and X2 are both in a low output state and the LED in the opto-coupler is off. When the input signal rises above the minimum set level determined by X2 its output goes high and sends a voltage output to the opto-coupler and then is retuned back to X1 with has its output low. Thus turning on the opto-coupler LED.
This give you a high output state until the input signal raises above the reference voltage of X1. When the input signal goes above the X1 reference signal its output goes high also. This blocks the returning signal coming back from the LED in the opto-coupler and effectively turns it off.
Once the input signal drops below X1’s voltage reference its output drops back to low state and turns the opto-coupler on again. As the input voltage continues to drop and passes below the reference voltage of X2 then it too changes its output state back to low and turns off the opto-coupler.

This allows you to have a minimum and maximum limit for whatever source you are using. This circuit is primarily used for the line voltage and frequency monitoring functions being they need to stay within an upper and lower limit window during normal operation.

ON – OFF DELAY TIMER

This is a simple time delay circuit used on most of the control circuits to act as a glitch filter. That is it’s primary purpose is to simply keep the control circuit from false triggering due to odd interference and false state changes from momentary dips or spikes that naturally occur during normal operation.

It uses a simple 555 timer IC setup to give a delay between its input state and output state change. R1 and C1 determine the time delay for both the delay on and delay off functions.
If the input state is high and a changes to low the 555 IC output will not change to low until the time delay has passed. If the input state were to change back to high before the time delay has been reached the output will not change states. It will remain in the high level.
If the input state is low and changes to high the 555 IC output will not change to high until the time delay has passed. If the input state were to change back to low before the time delay has been reached the output will not change states. It will remain in the low level.

Depending on the function it is being used for the time delay can be set for any where from 1 to10 seconds. Personal choice is up to the user. I prefer a 5 second delay in order to ride out line voltage dips and peaks from higher powered devices around my home turning on and off.

Basic circuit diagrams are below.