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analog8484 Senior Member Joined: 11/11/2021 Location: United StatesPosts: 108
Posted: 10:31pm 17 Feb 2022
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The nanoverter looks very interesting but after reading many posts I still have some questions:
* Does anyone run it with AC coupling to grid-tied inverters with frequency shifting in a production system? And how well does it work?
* Can it be used for a 12V inverter? I would like to use the 12V LFP battery I already have.
* Is a custom toroidal transformer required? Related question, has anyone used a transformer from a Power Jack inverter without mods? Any serious problems?
I am looking for the quickest way to get a smallish (12V/2000W?) inverter running with the nanoverter and GTI so I get familiar with it before moving on to more complex/optimized versions. Suggestions would be appreciated.
poida Guru Joined: 02/02/2017 Location: AustraliaPosts: 1418
Posted: 03:03am 19 Feb 2022
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Hi
nobody has used the mains freq sync function. It was provided for those who like to experiment and blow things up.
If course it can work with 12V DC supply. It needs 15V for the gate drive and 12V for fans and 5V for logic. Since all our builds are 48V we use a offline supply bringing 15V. These are cheap and run down to about 35V
A custom toroid is not needed. When testing, you can use any transformer you have. I have used 60VA 250V->25V toroid, a 240V->12V IE from a UPS and modified 1.5, 2 and 3kW toroids with self wound primaries.
I would start with the picoverter, get it running. That board is far simpler to build and debug. Then maybe make the nanoverter with mains sync if you need that function.
What power board do you think you will use? If it's one of the madness boards, such as the one I drew up then you will need to bypass the TIP35 based voltage regulator and give it about 16 - 17V from a separate supply. It takes the DC input as it's supply so there will be a few volts drop from the 12V battery and that is not enough for the totem pole transistor drive.
I highly recommend you go for a 48V battery. The DC current levels are 1/4 the size so things are easier overall. No mods needed with the powerboard. But it's not my problem if you stick with 12V.wronger than a phone book full of wrong phone numbers
analog8484 Senior Member Joined: 11/11/2021 Location: United StatesPosts: 108
Posted: 02:17am 20 Feb 2022
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@poida
I would like to first thank you for creating the nanoverter.
Also, thanks for the picoverter suggestion. I wasn't aware of it until now.
I understand that 48V and the Madness power board would be better. However, I don't have 48V battery or charger at this time so I would like to get started with what I have. I do plan to get to 48V and the Madness board eventually when I have better understanding of the nanoverter.
For now, I was thinking getting a low cost Power Jack inverter (e.g. https://www.powerjackpowerinverter.com/index.php?route=product/product&path=86_127&product_id=172) and only swap out the controller with a nanoverter/picoverter with appropriate buck-boost converter for power. Do you see any major issues?
I am hoping it would allow me to get something running quicker. And I imagine I will probably blow up some things in the learning process so a Power Jack inverter would be handy as the parts are relatively inexpensive and easy to get here.
Regarding sync to mains, that's quite interesting but not quite what I was referring to. I was referring to an off-grid scenario where grid-tied inverters sync to the nanoverter to produce power. Specifically, I would like to use the nanoverter with frequency shifting control to curtail AC coupled grid-tied inverter power when necessary. My understanding is that the nanoverter can already produce AC output at different frequencies in a stable manner so frequency shifting seems doable? Your thoughts would be welcome.
This is all in the planning stage at this point but hopefully I get to do it and share the findings.
Murphy's friend Guru Joined: 04/10/2019 Location: AustraliaPosts: 648
Posted: 04:45am 20 Feb 2022
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It appears you are trying to do something I'm doing in a more complicated way.
If you connect the AC terminals of a nano inverter to the AC terminals of a grid tie inverter you create a mini grid - you *must not* connect it also to the street mains grid, if you do you blow up your nanoinverter.
Anyway, solar power you feed into the grid tie inverter can then 'back charge' your battery via the nanoinverter. So far so good. But, all the available solar power gets dumped into your batteries and if they cannot accept that charge you'll cook them. You cannot regulate the solar input easily.
So you need a way to disconnect the grid tie inverter when the batteries are full. This is far easier to do by disconnecting the *AC* between the inverters with a suitable double pole relay (I use one with 30A AC contacts and a 12V coil). No need for fancy frequency shifting which may or may not do what you want.
This is what we call a 'bang, bang' control. You need a voltage sensing relay that senses your battery voltage and has an adjustable hysteresis. This controls power to the AC relay between the inverters.
When the battery voltage rises to the point you pre set on the voltage sensing relay it interrupts the 'mini grid' connection between the inverters by removing power to the 30A relay coil. The grid tie inverter senses grid outage and shuts down.
When the battery voltage falls to your preset value the voltage sensing relay turns on, re connecting the two inverters and the charging resumes.
No problem if that happens after dark as there is no solar input and the grid tie inverter is on standby until sufficient solar input resumes AC output.
I have used this system for a few years now and it works flawlessly. I initially tried control by interrupting DC from the solar panels - bad idea as whatever you use for switching does not last long with high voltage DC. Much simpler to control the AC side. Set the voltage difference between 'charging' on and off to suit your battery capacity.
noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 512
Posted: 10:41am 20 Feb 2022
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its funny Muphey's friend, ive done almost the opposite to you for years, the dc rout, using PWM into the " high voltage dc " side... using and good quality suitably rated mosfet or IGBT it works fantastic.. the ac rout works great too, one of my GTI's has that setup ( the other 3 dc pwm)..
https://a.aliexpress.com/_msOCFte
I use a couple of these for monitoring my system, they come with a built in relay control, ether voltage or current ( high or low, setable) which I use for 1 of my GTI's with a suitable relay on the ac side.
as stated, you can regulate GTI's quite easily without going to frequency shifting, Madness even had some dc side regulator boards with code on offer at one stage ..
I know also clockman had a really good write up about the methods he also uses on his system... also very effective...I think it works !!
analog8484 Senior Member Joined: 11/11/2021 Location: United StatesPosts: 108
Posted: 11:47pm 20 Feb 2022
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@murphy, @nonya
Thank you for your input.
I have used relay based control but it has the drawback that it's all or none and after every turn off it takes 5 minutes (UL compliance) for the GTI's to turn on again. Also, modern GTI's can proportionally adjust output power based on frequency so it's not all or none. These are main reason why I would like to try frequency shifting.
Regarding batter voltage based control, they don't work well for lithium based batteries so that's another area that I would like to find a better alternative. I am thinking using the SOC info from BMS would work better. Edited 2022-02-21 09:48 by analog8484
noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 512
Posted: 12:47am 21 Feb 2022
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why I use the old aurora inverters, can adjust the reconnect time to 5 secs...being off grid, " ul certification " isn't needed..
I'm sure poida could help you with frequency shifting if needed..I think it works !!
Murphy's friend Guru Joined: 04/10/2019 Location: AustraliaPosts: 648
Posted: 01:51am 21 Feb 2022
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Not so in my case, with a 300Ah lithium battery bank.
My GTI re connects in 20 seconds but even 5 min is acceptable IMO unless you have clouds going over in 5 min sync .
The trick is to also have an alternative charging method.
The GTI and MPPT at my place take the bulk charge every morning. Once the battery bank goes full the MPPT charging is sufficient for the usual daily loads, thus maintaining battery voltage. Heavy loads cause the GTI charging to commence again.
A while ago I used GTI charging only as I was working on my MPPT unit. Using only that method caused a lot of GTI on/off sequences. Perhaps you can give that some thought.
Murphy's friend Guru Joined: 04/10/2019 Location: AustraliaPosts: 648
Posted: 02:00am 21 Feb 2022
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I tried the DC rout nonya, first with madness's original suggestion which cost me a few blown mosfets. Then I tried expensive IGBT's which lasted only a little longer. Never tried to control it with PWM after that, the 'on/off' failures made me cautious about high voltage DC .
My GTI has a 3 string solar input, 1KW is connected to each. So on the DC side I need a 3 pole switch (IGBT/Mosfet). In my case the AC rout was far simpler.
analog8484 Senior Member Joined: 11/11/2021 Location: United StatesPosts: 108
Posted: 05:08pm 21 Feb 2022
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That's an interesting approach. Do you have a separate PV array connected to the MPPT?
This is more consistent with what I have seen from others using lithium batteries.
Murphy's friend Guru Joined: 04/10/2019 Location: AustraliaPosts: 648
Posted: 03:47am 22 Feb 2022
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Yes, there are actually 5 strings of two or 4 panels connected to my MPPT. Total 2KW on the labels, I have seen 2.4KW on a good day. I use 30A/100V Schottky series diodes at each string output to combine them to one MPPT input.
This is necessary as they are second hand panels of varying make & wattage. Those diodes can get hot, they need to be on a decent heat sink.
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.
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