Grid Tie Inverter Schematic

[danGPS]

Hmmm...

thanks to all for the great info...esp TCMTECH..and yes I to have seen PHD disease..

I have ideas and questions..

1) Why not switch AC in a random way so as to "spread" harmonics in frequency domain?? Variations of this trick are done to reduce EMI from very high speed clocks, etc.

2) Why not make every medium size PV panel with its own inverter module?? Does %eff suffer?

3) If every panel had an grid tie could each one also have a low cost wireless interface ( blue tooth? ) that reports that panels health to site PC??

4) For truely large installations A GPS receiver for panel position also?? Single chip receivers are now very chep..

5) How is the line phase sampled?? What about unwanted coupling of GT to phase sample of input?

6) GPS receivers can produce VERY , VERY accurate 1 pulse per second time that is same every where. Can this be used in some way to make GT better? A related question is phase movement of GRID phase to 1PPS phase..hmmm I will measure and post.

-Dan

 

[tcmtech]

I am not sure what everyone elses thoughts are on size an number of GTI's to use.
But for me I know cost per kw does go down rapidly with size increase And there is a slight efficiency gain too , but you also spend more up front for making one big unit.

Given that you are probibly working on a sytem that is build as you can afford it I would go multiple small units instead. Spread the cost over a longer time scale and you also have that advantage of if one goes down you still have others working.

I wish I still had my old low frequency power line spectrometer. I could post an actual picture of what my GTI looks like on the line side at full tilt.
And when standard power draw devices are on most of them have more odd harmonics coming from then most people would believe. The power in your house is not as clean as you may think.
Put a drop of tap water under a miocroscope. See all the little things you did not know were there? Your house power is like that too! If you start looking at your home power up close like that all of those with electrical OCD would never turn on another device ever again! They just might be letting more harmonic bugs roam free on the power sytem, OH NO!!!!
Use good proven ac line filter design for the power range your working with and leave the miroscopic harmonic bugs alone! They are there and they will always be there its just part of an AC system.
I use a real time voltage sampling method for phase monitoring. That simple cotrol transformer driving the H-bridge is a very reliable and simple way to make it work. just make sure you have a wide enough deadband for the line side (power ransformer) wave form to change from its positive half to negative half. (zero crossing region)
As I have stated before starting and stopping the H-bridge conduction cycles at around 20-30% of peak voltage works very well. And there is no complicated phase formulas to work with!
I found that region works well by trial and error. Burned up a few IGBTS finding out that the area of a sine wave close to the zero point is useless to try to dump power on. Vicious high amps to turn on and off and little usable counter emf to work against! harmonics generator anyone!?!
Plus the transformer and power factor correction need a dead zone for them to resonate properly. That way the line side winding is still working with a sine wave even if the switch side is dumping square wave power.
And when you are sampling the line voltage for phase reference do it on the line side of the filters not the GTI's power transformer side! far far less chance of starting a runaway resonance/feedback loop!
Believe me, a odd frequency power resonance or ossilation does not go well with anything in the house! Flourecent lights grumble and chatter, the refrigerator compressor makes an terrible sound, digital clocks loose track of time and then the harmonics police will come looking for you!

Bluetooth the the GTI sytems. That would be interesting if you could get each to supply a real time output of whats going on. Data log the whole system. I bet a university or company doing alternative energy research might pay a bit to get real life system log info.

 

[tcmtech]

Wave Realitivity and your GTI clock

Here is something interesting to think about. calculate the length of a 50 or 60 hz wave. Lay that over the distance of your continent you live on. Now factor in that power plants are dumping onto it at all points along it and power is being pulled off of it. Then factor in phase drift caused by the load changing locations durring a 24 hour period. And the supply point does not have a fixed origion. Every power plant and every load along that wave length is floating not static. The master wave ties everything together but it does not have a fixed point of origion or end.

Interesting! No true single master point to reference things to on a time vs wave point scale.
Perhaps thats why clocking does not so work well. The phase peak will always change depending on where you are on it and where the power is coming from and going to at that instant. It is only relative to your position not fixed.
Washington state is some degrees off from florida if you do the math. But who is the master reference? Is washington running faster than Florida or are they running behind Florida? Who is front and who is back?
See the wave relitivity problem?
You have a multiterawatt standing wave but yet there is no true ends that it is bouncing between!

 

[danGPS]

Hi All;

I am into GPS so I know a bit about that and see it getting into everything..

Yes now I understand the deadband , that is by looking at line phase when you are not "ON" you get it "unperturbed" grid phase. Clever.

I had another idea on the distributed approach, that is a GT in each PV panel.

My understanding is that filtering and magnetics of size are involved with "true" ~sinwwave approach??

Is it possible that with a distributed approach the resulting inverter output is a sum of approximate modified sinewaves?? ( is the GT zero crossing not now a integrated sum of zero crossing time instants whose mean is ~1/60 sec, but average period set precisley by crystal reference)

If the start stop time is also modified in a noise like fashion as described above could it be that resultant sum has better sinwave properties with smaller magnetics ( lower cost?)

By using blue tooth is it possible to coordinate the sum in fashion that improves %eff also??

Just for giggles one of the first GPS displined clocks , design by HP, was used to record Time of Arrival of power line fualts at distant locations..then by propigation of wave a distyance can be calculated, location of fualt found.

-Dan

 

[danGPS]

Cheap Power Line Spectrum??

Hey TCMTECH;

I have seen "inexpensive" software that takes audio input from PC and does FFT on it, plots spectrum.. could that be a low cost power line spectrum analyzer??

You might have to modulate a carrier at ~ 5 to 10 khz to get into bandwidth of this instrument, but once cal'ed it should be fairly honest interms of spectral lines ...the ine I saw had sub hz resolution...think it went from low hz to 20KHz..

-Dan

pS excuse typos..Fault is not FUALT.

 

[be80be]

There rated at 30 amp 1000volt how you get "15-20 amps" 3 of them where controlling a 30amp 460volt motor they are made to handle 2.7kw . So if they can handle 2.7 kw at 1000 volts looks like they could easy pass 75amps at 12volts maybe even a 100amps and not get hot seeing I have heat sink that is 20 pounds to go with them?

 

[tcmtech]

DanGPS first.
neat way to use GPS. I think i understand the priciple you are talking about. its sort of similar to those line thumpers that echo a wave off a break in a electrical line. but much bigger and longer distances can be tested. or am i way off?

Second Part : what?
Actualy I sort of get it but i need a better expaination. It still seams like a complicated line noise maker just waiting to happen. But again I could be completely missunderstanding the concept your trying to discribe.

Third part: never thought of using an audio spectrum program that way!
If it works I am putting it on my CD in the Dumpster Diver tips section. And I will credit you at this site for it!

Be80be

True logic. But...
Heres the problem. when you switch them on into the transformer you are putting that 12 volts aginst the sine wave low down by the zero end. Your esentialy trying to dump 12 volts into a far less than 12 volt counter electromotive force.
If you can measure your transformer secondary resistance. Say its a good sized copper winding of say .05 ohms. Dump 12 volts across it you get 240 amps. 12/.05 = 240
put even 6 volts counter emf from higher in the sine wave and you are still pushing 6 volts back above that. 6/.05 = 120
Actual inductance will reduce that number more but as you can see thats how you get a high amp load at every half wave turn on but then have to turn off that high amp load at the end of each half wave.
Real life taught me that one. I kept popping IGBT's for no apparant reason until I got a hall effect type DC current sensor and hooked up my O scope to its output.
my average amps were only about 10 or so but points where the IGBT's were switched on and off were pushing 40 plus.
I know that PFFFT.... SNAP sound by heart! Semiconductor switch distruction!

With proper current control feed back then yes you could possibly push your 30 amp rated transistors at 20 amps plus per device. BUT it would still be risking a current overload and possible die burn up. You would have to check the actual manufactures specs to see what they are rated for disipation wise in this type of switching application. IF your in the safe zone your fine but get close to the edge and PFFFT!

Real world inverter circuits that I have studied and repaired have a typical 4 to one current rating and a two to one voltage rating over their actual running amps and running volts at the switching devices.
A good model plasma cutter with a 25 amp draw at 240 volts typicaly has the switching H-bridge circuit built to a 100 amp 800 volt or higher capacity per corner of each leg.

Some do go less than that but are more prone to burn outs and others go even higher and rarely burn out. Century Vs Hypertherm! Snap-on Vs anyone but century!

Snap-on, craftsman, marquette, solar, napa, some black and decker and alot of the generic welder and plasma cutters are made by century! Yep your high dollar Snap-on is a Century! Now arent you proud to know you spent 3 times the money as what a century with the same ratings costs to help fund a poor starving multi millionares rediculous hobbies!

 

[danGPS]

crazy idea?

You asked for a "clearer" explanantion of my idea on "randomizing" a modified sinewave..

Actually I see this as part of the sum of modified sinewaves from a distributed GT , say for 20 or so panels ..

If you modulate the starting/ending angle in a random fashion, but keep the overall period fixed via xtal time base that should spread the harmonic lines generated by modified sinewave? Pure harmonics can only be generated when all timing edges remain "fixed" ( my understanding)

Are you moving/modulating start/end angle of modified sinewave to achieve current control?? If so then I would expect a Harmonic line to have a width somehow proportional to rate and depth of modulation. In other words if you zoom in on a harmonic line , its not a line but is widened by your current control method?

If instead you add randomly ( by small angle deviation) on top of the current contol point you seek ,whose average value is zero then you have not modified average current "command" but you have further widened or spread any harmonic line??

I see this idea to work inconjunction with summing multiple panel based GT units in such a way that the sum of modified sinewaves has lower harmonic energy per "unit bandwidth" , and that due to random nature has lower probability that positive adding of modified sinewaves increases harmonic power levels?

If I decrease harmonics I should get a better sinewave, right? Is it possible such a method of an array of GT ( 1per panel) needs lower cost filtering(smaller magnetics) and acheives higher %eff ?

I will try and find the HP article on the power line fault detection using GPS clock and post.

-Dan

 

[danGPS]

HP Smart Clock AppNote/ with app to Power Line Fault Det

see attached for the app note from HP that describes ( as part of it) the motivation for HP developing that product, which was intertie fault detection over large distances.

 

[tcmtech]

Interesting!
I have not had to aproch the real world problem of multiple GTI's running high total power outputs yet. But I feel you do have a good and possibly very valid point. Plus what you were saying about spread out of harmonics seams reasonalbe too.
I do think that multi GTI setups could possiblly produce some harmonics amplification problems, maybe.
However I tend to aproch things from the simple (Complexity + time + money) Vs (practicality + reliability + user intelegence) Formula.
Complex, hard to build, and difficult to understand makes the potential user less likely to want to use it.
Plug it in, turn it on, walk away and never look at it again. That sells!
Also production issues are a real factor on a DIY anything. Can it be built and work reasonably well just from cheap common found parts I already understand?
Or is it potentialy difficult to build and parts are expensive and hard to work with?
Cheap, simple, reliable and functional always sells!

I will take a 60% top efficiency that is user freindly and reliable over 95% efficiency thats difficult to work with or on.
After all we are talking about using energy sources that only cost what it takes to capture them, right?
Do I spend $500 on a GTI that runs 95% efficient conversion from my 100 watt solar panel or do I spend $150 for 60% efficient GTI and just buy another 100 watt panel to make up the power loss difference with interest?
It purely comes down to how each person aproches the concept.

I am leaning hard on the simple, low buck reasonalble to build end with the help I am giving here. But I do also know there are more complex ways to make this work with some added gains and benifits. But right now I am still focusing primarily on simplicity and actual how it works theorys.

Start basic and go up. Each person will top out at where they are comfortable. Some will be running the basic two transformer unit design years from now, others will have moved on to far more complex and complicated designs that far outshine my own!

 

[danGPS]

I agree, Keep it simple

TCMTECH;

I get your point, I just wanted to share my ideas with you and others here , you have given away a lot of info here, thanx for that.

In terms complexity/price, yes complex is usally less reliable, but from cost standpoint if you get more $$$ in return maybe its worth it??

i am thinking from a mass product point of view, but from a hobby point my ideas are not practical. I do like to dream!

The ideas I have I believe can be implemented in a very low cost way, but reliability is a different issue.

I have not built a GT (yet) , and my skill set is elsewhere , primarily RF/Communications/GPS etc. I do know a smidge on Power electronics, but I beleive in cross polination, perhaps my view will shed light and visa versa,

-Dan

see DKD Instruments for more info on my interest and writings..

 

[tcmtech]

Good to know. I started posting here to help others and to find realiable sources for answers to my things that I am not that familiar with too. I specialize more towards power control and power supply systems in the real world enviroment. hence the reason I dont post a lot of complex math equations.
Theory is great, but often transfering that theory to real life is unfortunatly often too bitter of reallity for some to contend with.
I to love to dream the improbible and often impossible too!
I am pleased to see someone that is willing to look at the low scale versus high prodution difference.
High volume will make the complex cheaper but it also makes the simple cheaper yet!

If it works leave it alone. If its broke fix it to be better.

 

[danGPS]

when is the CCD going to be avaliable?

TCMTECH;

when are you going to post your CD on ebay. I'd like to buy one..

-Dan

 

[tcmtech]

I dont know just yet. real world time frames are hard to pin down. this last week I have Been lucky and had a lot of free time. But having a service business that can literaly change over night.
I seem to get one or two jobs every year that are one weekers that get streached out to 3 or four, I did a job two springs ago that was a one weeker. I came home 7 weeks later! after week three I said I need to go. They started paying me in cash everyday to get me to stay!
another one of those and it could be next July before I get it done!
I am about a third of the way done with the rewrite but I still need to do the actual build up pictures, construction discriptions, schematics, and blueprints for each size of unit I am going to put in it.

Right now I am thinking of going with these.

1: A low dollar 12 volt 100 watt basic no frills unit.
2: A 500 watt two stage 12/24 with basic analog but full function controls.
3: A 2-3 Kw that runs at line level voltages with basic PLC control system options.
4: A 10 Kw multistage with the PLC control system plus the actual input from the local power company towards it being a legaly certified hookup.

But again time will tell. Some of this is going to be limited simply by the local weather. If this far below normal and heavy snow crap keeps staying I may have to skip the big one
Just because of unreasonable working condtions.
I am also a bit of a perfectionist too. Being my first true DIY publication I want it to look good and read well. First time impressions you know.
I have to trim the math down to get it to a level most people with good basic math skills and a good calculator can use.
I really am shooting for true practical designs that a high school student with a good electronics class could actualy build. Or a college student with a good electronics or electrical background could work with.

Got to keep it hippie / enviro-nutter friendly you know! Their the goofs that will pay $20 and never actualy use it to build something but will adopt it as a bible if its done simple enough and tell all of their goof friends to buy one too! Or they will just copy it and I will have sold only one and it will be on some enviro-nutter website for free in the over unity devices section with all the input watt numbers divided by 3 and the output watt numbers multiplied by 500!

So if any of you have a size you would like to see and everyone can agree on I will consider it!

 

[danGPS]

Tcmtech

I assume you know that you could also list your CD "book" on Amazon if you get a ISBN number? You can buy a ISBN number cheap thru a number of small publishers, once you have that ISBN# I believe you can list your text on Amazon.

Check the details out with the independent pub's and Amazon.

-Dan

 

[tcmtech]

Nice.... Didnt think about that either. I see lots of potential here! but also more work too!
I will look into it some more when I have more time.
Its definitly worth looking at. I would love to have a constant low flow cash source!

 

[acedrafter]

Your CD "book" schematic drawings

Hi tcmtech, I’m very interested on your presentation about “Grid Tie Inverter” various schematic design and “Do It Yourself” electronic applications. Maybe one day I will have the opportunity to build my own “Do it yourself Power Inverters” for my house, car, motorcycle, and RC model airplane. Meanwhile I am content to dabble on electronics circuit schematic and reading, participating on QA Electronic Forums until I get more experience on this field. Finally to keep my curiosity about this subject online, I would like to volunteer on my spare time to draft your schematic, concept sketches into engineering drawings for your CD “book”.

 

[tcmtech]

Seriously?
Wow nice it would be so helpful!
I will have to get may scanner back from my grandparents, but yes I could easily send you drawings and hand sketched circuit diagrams.
I could use the help of a good Cad drafter! You will get full credit on the CD too!
Words are fun but people still can get more from a good look at pictures, diagrams, and schematics!
Or if you just need a good reference item for future job hunting this would definitely put a bit of shine on a drafters resume!
I always share the wealth to anyone that puts forth a true and valued effort.

I have a few local friends that have agreed to give me useless ideas and pointless info in return for kick backs of a most generous nature as well.
So there is a bit of screening and value testing involved first!

And as a realist I will openly say there is still that chance this thing could be a total dud and have no sales or interest what so ever! And everyone involved will be wishing they used a false name on the credits!

 

[Val Gretchev]

Another Example

Here is a design I have been working on in 2008. I built 2 boards but lost interest along the way.

 

[tcmtech]

Nice. Very well thought out! Definitely got mine beat on complexity!
I wish I had the Cad skills to do up circuits like that!

Did you ever get it to work? I mean an actual functioning unit?

I have seen a few others make elaborate designs that had great potential too but unfortunatly over complcating a simple process dragged them under. Too hard to build and trouble shoot and too expensive to get a reasonalbe payback time on avoided cost if they ever did get them working properly.
Still like your concept looks though. Very profesional looking an all aspects!