Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
Ralph2k6 Senior Member Joined: 24/09/2017 Location: AustraliaPosts: 129
Posted: 06:57am 10 Jan 2018
Copy link to clipboard
Print this post
Don't forget Dazza that the famous OzInverter is not a solar charge controller. It takes the battery voltage, inverts to mains voltage and voila.
You can use a grid tie inverter to back feed the OzInverter to recharge your batteries. Or charge your batteries separately.
Some of the clever boffins here have also designed controls to limit the PV DC feed to the GTI to prevent it overcharging the batteries through the attached OzInverter (its a minigrid arrangement)
Hoping I'm not mistaken either..Edited by Ralph2k6 2018-01-11Ralph
So there is no way of using an Oz inverter direct from PV without using battery to power it?
So where to from here?
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498
Posted: 08:04am 17 Jan 2018
Copy link to clipboard
Print this post
Just get some batteries, even 4 of those 7AH sealed jobs would give you something you can work with.There are only 10 types of people in the world: those who understand binary, and those who don't.
Hmm this is about where I started and was advised battery wasnt the best way to go, the only difference from what I proposed in my OP is the voltage.
warpspeed Posted: 17 November 2017 at 1:18pm on page 3 his idea and it seemed workable and was what I was running with but seems I misunderstood what he was suggesting.
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498
Posted: 12:43pm 17 Jan 2018
Copy link to clipboard
Print this post
Okay you don't need a battery if you do that although Warpspeed says he will add a battery to it. There are only 10 types of people in the world: those who understand binary, and those who don't.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 09:43pm 17 Jan 2018
Copy link to clipboard
Print this post
The high voltage dc system system I have right now, that has been running very reliably for two years has no battery. It uses grid power at night (via a dc rectifier) and solar during the day. It load shares during a seamless changeover at sunrise and sunset, or during very cloudy weather.
It feeds nothing back into the grid and so gets around all of the problems that go with having a smart meter and all the rules and regulations that go with officially installing a grid tie system that feeds power back into the grid.
I have a 100v 5Kwh lithium battery, that will eventually be connected up to provide night time power. But I want to get the fairly complex battery management system and battery charger fully developed and sorted out first. I don't want to damage the battery by being in too much of a hurry.
A battery is not economically viable. My night time power needs are so low that its going to take at least ten years to recover just the cost of the bare battery. I am doing it only for the fun and challenge of it, so I can afford to be patient and very slowly get the battery part of it up and running.
The other parts of my system, solar controller and inverter are very unusual and would be difficult and not really practical to copy.
I am interested in power electronics as a hobby and wanted to try out some fairly original ideas that I am still developing and messing around with. Its my own quirky nature to try out something very different and experimental and have the satisfaction of overcoming any problems.
So for me, the going off grid part is just a bonus. My real motivation is in trying out strange and original ideas, and building something quite unique that nobody else has, and get it working really well.
The overall idea is quite simple. Its just that the complex way I have implemented it would not be easy or practical for someone else to copy exactly. And that is the problem.
For instance, I have three phase power available here, so giving exact details of my three phase rectifier are not going to be of much use to anyone that only has a single phase grid connection.
Cheers, Tony.
George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308
Posted: 10:18pm 17 Jan 2018
Copy link to clipboard
Print this post
But it would be very informative for those of us who DO have 3 phase!
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 11:52pm 17 Jan 2018
Copy link to clipboard
Print this post
Haha o/k George, you win.
A three phase rectifier produces some really nice dc with minimal ripple voltage as the wind turbine guys will already know.
The problem with an inverter is that it draws a very heavily pulsing load at 100 Hz which may not be a problem from a big battery, but it becomes more difficult to do from a rectifier, especially a single phase rectifier where the inverter and mains frequencies may be constantly drifting in and out of phase. A three phase rectifier solves all of those types of problems, especially if the dc output voltage is fairly high, requiring minimal extra filter capacitance.
Now my own sine wave inverter requires split high voltage dc power supply rails, because its a half bridge design, ideally about +220v and -220v dc to provide 230v rms (325v peak) output.
As a three phase six diode bridge produces a dc output about equal to the voltage peak, three transformers will be required to lower the mains voltage going into the rectifier to produce the required dc output voltages.
I used three Inspire 1.5Kw grid tie inverter transformers to do that, but they are not connected as normal isolation transformers, but as auto-transformers.
That has several benefits, the biggest one is that the 230v primary and 135v secondary are now connected in series across the incoming 230v, which greatly reduces the flux in the transformer core from 1.5T to around 0.95T and no load idling current of these three monsters shrinks to around 11 watts each.
The other advantage is I can use the three original unmolested Inspire transformers without going through the whole rewinding drama ..... and I am lazy.
That should give me something like 4.5Kw of solid dc with excellent voltage regulation and a minimal idling power loss of only 33 watts. (0.8Kwh over 24 hours).
Its turned out to be vastly larger and much more powerful than it really needs to be for my very modest night time loads. But its now built and working fine, and it will do until I get my lithium battery system up and running.
would the version two be able to handle these panels in two series strings at 60v
I chased up the guy that had a pile of dead inverters for the toriods and fets but unfortunately for me he had a clean up for Christmas and they all went for scrap :(
he didnt have any Inspires any way.
so if the Oz will take the 60v and I want to continue along this path what fets and how many would be ok the run at say 1.5kw continuous with fridges and evap air con starting?
I also see no reason why your 3 phase set up cant be use on single phase, just means 3 times more current being pulled on that one phase for the same output Edited by Dazza123 2018-01-19
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 05:01am 18 Jan 2018
Copy link to clipboard
Print this post
There is a bit more to it than that. It could probably be made to work fairly well if the inverter was correctly synchronized to the grid, but that adds complexity. It gets away from just using a simple free running inverter.
It could very likely be arranged to work so that the inverter draws its high current peaks right when the mains is going through its peaks. But you would need a modified inverter for that. I have three phases here, so it was much easier to do it the way I did.Cheers, Tony.
I currently have 4 Trina 230w panels with the specs in picture
I a version two board as pictured up this page
I have a eg002 board.
I did pick up 5th panel that is so close in specs it could be a twin and plan to look for more.
Got to 6 pages here and still no closer to a plan.
so short of going back to the original idea of a small battery bank and an inverter the only progress has been to go from 12v to 48v to reduce currents
The orignal thought was to use solar during the day to run most things around the house except high current things without any back feed.
Warpspeed your idea appealed in that it was seamless and was not grid tied or considered connected in the sense anyone could say you cant do that.
So with what I have and maybe an extra KW what's your thoughts for a direction, the idea is not to go off grid but to use solar while the sun shines.
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 10:21am 18 Jan 2018
Copy link to clipboard
Print this post
1/ Accumulate enough solar panels to cover your normal expected daily loads, more is always better.
2/ Decide on a system voltage, the higher that is, the more efficient the whole thing will be.
3/ Build an inverter and dc rectifier to suitCheers, Tony.
Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498
Posted: 12:08pm 18 Jan 2018
Copy link to clipboard
Print this post
Is there a reason you don't just go to a grid tie system?There are only 10 types of people in the world: those who understand binary, and those who don't.
George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308
Posted: 01:18pm 18 Jan 2018
Copy link to clipboard
Print this post
I bought a complete 4KW solar setup last weekend for $550. Bought another 3 KW system today For $350.
I have 3 phase with a smartarse meter on one phase and would like to explore this concept of feeding the leg with solar power without backfeeding which I can't do with out it registering the excess as a charge.
I'll have to read through this again when I'm not so damn tired and can digest it more.
I'd like to feed the leg with the smart meter that goes to the AC. Was thinking I could wire it back to the AC itself so when it turned on it booted up the GTI. If I measured the draw and had only say a 1.5KW inverter, I could supply the bulk of the power and lessen the grid consumption.
Thing is, the rest of the time that array would be wasted. Is there a way to feed another phase and divert to the other phase automatically when the AC kicks in?
I'll revisit this next week when upcoming pressures are over and I can think better. :0)
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 07:58pm 18 Jan 2018
Copy link to clipboard
Print this post
It does not matter if the array is wasted. If it supplies all of your day loads and you are getting all your daily power for free, any available excess does not matter.
The problem with grid tie and a smart meter is you cannot hide, and you then come under scrutiny and MUST comply with all the rules. The rules will constantly be changed in a way that you will always lose and the power utility always wins.
What you feed back becomes valueless, so might as well just not bother feeding anything back at all. Stuff em !Cheers, Tony.
George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308
Posted: 11:57pm 18 Jan 2018
Copy link to clipboard
Print this post
My setup is a little " Different" 3 phase power, 1 electronic ( rather than proper smart) meter, 2 analogues. solar goes into the circuits which wind the spinny meters backwards if there is any extra power from the household loads.
Only thing now on electronic metered phase is off peak hot water and 1 Leg of AC. Electronic meter counts feedback as a charge so can't do that. What I want to do is have panels feeding that circuit when the AC is on, a limited amount of power ( so as not to pay for my own power) and when the ac is not on, the power goes to a different circuit to wind back the spinny meters and not waste the power.
What I want to do is feed power to one circuit and use the leg the AC is on (tap onto the compressor lead for signal) to trigger the power to be diverted and have it going to one of the other phases when it is not.
That would be the gran scheme anyway!
:0)
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 12:27am 19 Jan 2018
Copy link to clipboard
Print this post
That could be done.
First thing is to monitor just the PHASE of the current with respect to the voltage. An Exclusive OR logic gate will do that.
It will be almost in phase when drawing grid power, and almost 180 degrees completely out of phase when feeding power back into the grid.
That will give you a simple import/export digital on/off direction signal telling you which way the current is flowing.
Next you need "something" to measure the actual current flow, and turn it into a frequency. A voltage controlled oscillator will do that. The higher the current, the faster it oscillates. No current at all, it stops (or almost stops).
Those two digital signals go into an up down counter. The counter counts amp/seconds (or whatever) it increases as you draw current from the grid, and counts down as you feed current back.
If it ever gets down to zero you know you have reached a limit where the power fed back equals the power consumed. And you MUST stop feeding power back. You don't want the meter reader guy to see negative Kwh, he just might smell a rat.
It may count up for several days or weeks, then count down with a few really sunny days. The spinny meter will either show something positive, or zero, but NEVER negative if you use your energy flow monitoring box to cut power to your grid tie.
It could be done in software, or in hardware with a counter and a few logic gates.
You may still get caught though. If the meter guy notices the disc is turning the wrong way. It would be hard for him to miss, he will be looking right at the meter when writing down the numbers.Edited by Warpspeed 2018-01-20Cheers, Tony.
George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308
Posted: 11:26am 19 Jan 2018
Copy link to clipboard
Print this post
Yeah, I was looking for a remote switch. Something I could put in the meter box so when the cover was opened it cut the power to the inverter causing it to trip out. Can't find anything with enough radio range though. :0)
I'm pretty sure at the last meter read they would have been spinning backwards. Forgot the reader was coming and left the inverter connected. When I went round the side I saw my tell tale broom resting against the fusebox cover had been moved.
Still have power connected so must have got lucky. Know when it is next time. post it note in front of me and written in the diary. Just have to put the broom on the box so I can see when he has been and turn things on again.
I was thinking of putting in a couple of extra dedicated Circuits for Bac..... heavy duty power requirements so maybe I should look at installing some relays or contactors in the box to disconnect the solar when the meter maid arrives!
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 07:55pm 19 Jan 2018
Copy link to clipboard
Print this post
The original idea of monitoring the power flow, and basically doing what the spinny meter does is still possible and quite practical.
Feeding only sufficient power back to just cancel out usage over time.
I have a smart meter here, dropping power usage completely to zero by going completely off grid may not be the smartest long term strategy.
What could be much more sneaky would be to still draw some small power from the grid, and make it look like a normal daily power load profile, but much much lower.
I could arrange things so that 90% of the power comes from solar and battery, but the other 10% always comes from the grid. Day or night. That may be the next step forward after I get the battery part of my system hooked up and running.
It could all be done on the dc side of the system. Monitoring dc current coming from battery, solar, and rectifier, and arranging things so that the rectifier always carried some small fixed proportion by throttling back the battery at night and solar during the day.Cheers, Tony.
Mulver Senior Member Joined: 27/02/2017 Location: AustraliaPosts: 160
Posted: 11:37pm 19 Jan 2018
Copy link to clipboard
Print this post
This is my plan also! Can the smart meters actually report usage profile? ie. hourly load?
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
Print this post
