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Author Topic: UPS and Growatt SP2000 unit  (Read 17833 times)
jonesy
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« Reply #60 on: November 25, 2015, 06:18:11 PM »

Under Mains failed condition to get the solar inverter to take the lions share of the load and the UPS to only provide the sync signal I will have to set the output of the UPS down to 220 volts. Like that the natural behaviour of the Solar inverter will go to a higher voltage because it is designed to push power into the grid and it will provide more power than the UPS. That is a balancing act that will require some experimentation at different loads.
Some things that occur to me.  The growatt gets its info from the clamp. With no mains import/export there during power fail, how will it know what to deliver.
The synchronisation of the solar inverter (GTI) with a UPS has been discussed to death and largely abandoned* due to the way a GTI normally operates.  However, if the growatt can just provide enough power to the GTI so there is no surplus, theoretically. If there is an excess (and there will be, as you have 2 closed loop controls there 1. UPS 2. growatt & GTI), there are 2 possibilities. The UPS objects to the power in, and blows the H bridge mosfets, or the UPS changes automatically into charge mode and charges the battery.
I don't think setting the UPS voltage down will change anything, as the GTI aims to export at just above the mains level ie current only flows between a voltage difference.
Check your GTI isn't the HF type, as IIRC the panels ie the growatt/batteries? are not always isolated from the mains. SMA have a guidance doc.
I personally wouldn't fit RCBO on the UPS/change over feeds.  Some GTIs specify RCDs where the panels aren't isolated, but I've not come across anything for UPS. The RCD reduces the availability. If you want one, you'll need to use either larger or time delay upstream to give discrimination.
Depending on your house earthing scheme, you must ensure that UPS is hardwired.  If not, if the supply plug becomes lose when on load, you will the board neutral/earth connection, thus leaving you with a floating mains system.
The fault current available from either the GTI, or UPS (or both) will be pretty low. What this means in practical terms is that a live to earth fault on a 32A breaker on a ring main will not clear in the prescribed 0.4s.  Possibly never, and IIRC you are not permitted to rely on the RCD to perform that function, but it probably would. Have a look at the sunnyisland for typical breakers - it'll be say 6A/type B.
Even if all your various items growatt/ups/gti are electrically isolated, each will have leakage currents through the (HF) transformers.  Whilst I'm not an advocate off earthing battery packs, you probably need to think about if and how you are going to keep one terminal near earth.
Interesting thread this.

*there is a successful modification of a UPS for off grid use here http://www.fieldlines.com/
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bxman
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« Reply #61 on: November 25, 2015, 09:51:07 PM »

Have either of you looked at the Nedap ?

I think most problems have been sorted out apart from their strange battery voltage  management ideas  but they are resolvable so I am informed .
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book_woorm
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« Reply #62 on: November 26, 2015, 03:58:56 PM »

Hi Jonesy,
          Firstly I'm asking a lot of questions of the Growatt guys and the subject of tapping off their battery for a UPS and marrying a UPS with the GTI will  go to their designers in Shenzhen once I've got a non disclosure and design rights agreement back from them. I don't mind if they eventually exploit the idea provided I get a royalty for it.

          This will be a hardwired system. Most UPS that I've come across earth the -ve terminal of the battery in the bridge and the AC floats, reliying on external bonding to the neutral. So how the GTI is earthed is a relevant question. Does anybody know how the Fronius IG series are wired up. That's what I've got at the moment. Getting the balance of power output right between the UPS and the Solar inverter is a matter of impedances and paralleling generators. I've seen multiple UPS's with paralleled outputs before. As the UPS has got to handle some motors without the benefit of soft start it will be rated far bigger than the mere arithmetic sum of the loads.

Hi bxman,
          I walked away from Nedap a couple of years ago because they would not release their control/monitoring software for 'local use' Everything had to go to their server and back again.  There are 2 problems with this, the user is relying on at least two third parties one of whom (BT) does not give a dam about somebody elses' operation critical control signals and what happens when Nedap go to the wall as a business or decide to stop supporting the product!! Didn't this happen with Encsys or have I got the wrong company. Nedap might not have been the most expensive but they were twice the price of some of the others.
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glyndwr1998
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« Reply #63 on: November 26, 2015, 06:11:00 PM »

My neighbour and friend had the enecsys inverters fitted with his solar pv. He isn't technical at all, and last year he knocked my door to say that all his inverters were off line and he couldn't tell if any of them were not operating as he had no way of interrogating them as the enecsys servers were now off line.

He has had 3 inverters fail too so this worried him greatly.
I did some research on his behalf and found freeware software so he could monitor his inverters locally himself. He was very appreciative to me for helping him out.

So it goes to show, local monitoring is the only way really, enecsys and nedap  have for sure taken the wrong road with that decision.
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book_woorm
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« Reply #64 on: November 27, 2015, 04:06:26 PM »

Hi Jonesy,
        I hope you di not think that yesterdays response trivialised the points you bought up on paralleling a UPS and Solar inverter, far from it, its just that I think the subject requires a more considered reply. The behaviour of the two units when coupled is something that I have on my list for a proper FMEA. There are a couple of learned papers on the subject of parallel operation of UPS's etc that use inductors for load balancing god knows what that does to power factors I need to do some reading up. Trouble is ones paper is in Spanish and the other in Danish, I have yet to find versions in English, when I can get hold of them I might understand the formula and form a view on the suitability of the ideas.

        I am already including a MOSFET and a LTC4359 control chip as a super diode in the battery supply to the UPS. This protects the battery from the UPS's inbuilt charger and the UPS from reversed battery connections. It should also stop a back feed through the inverter from the AC side. People tend to forget that once there is a positive voltage difference between gate and source on an N channel MOSFET that current can flow in either direction so I guess your worried that the bridge circuit will act as switched diode bridge when the GTI tries to push excess power into the UPS. One way that I have in mind to stop this is to use the Growatt's natural abilities to reduce both import and export to zero. This could be done under emergency conditions if there was a CT between the UPS and the 2nd Consumer unit. How to switch between the two is currently exercising my mind as I would need to tap into the UPS's transfer signals, but I don't want to ask questions about the CT's circuitry until the 'non disclosure' agreement is in place.

        On the subject of protection; Some of what I have seen so far appals me and even the best is not as good as it could be. BS7671 calls for UPS's to be able to operate distribution circuit protection devices (para 560.6.11). Now if you are feeding a 32amp ring main from a 2KVA UPS then you've got a weasel pee poor design anyway and I agree the breaker probably would not trip.  Glyndyr1998 is using 6KVA and 10KVA UPS's so it is something he needs to carefully think about with the smaller unit but the bigger one will be ok. For myself I'm looking at a 3 or 4 KVA UPS feeding radial distribution circuits (Rainwater pump 4 amp, a couple of fridges/freezers an amp, Solar Thermal system controls another amp, CH boiler controls 2 amps and ethernet routers another amp) There are 5 motor start currents to be accommodated but the chances of then all cutting in at the same time are remote. I've initially chosen RCBO's in the main consumer unit for the AC input to the emergency system because you need to protect the other circuits in the house from the UPS etc playing silly buggers. You don't want an earth fault/line neutral imbalance in the emergency circuits throwing the whole board off. However given the high failure rate on RCBO's and the need for double pole isolation I'll probably change them for a RCCB and individual MCB's.

        On the question of Mods to UPS's I've heard of the field lines web site but I never been able to get in to it do you have any other references. Also if you have any other relevant thoughts about what should go into the FMEA please let me know.
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glyndwr1998
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« Reply #65 on: November 27, 2015, 06:47:45 PM »

Hi bookworm,

you have obviously put a great deal of time and thought into your system, I don't know what your experience is, but it sounds considerable, I'm mechanically biased myself so most if not all of what you discussed in the previous post went woooshhhh straight over my head.

I will not run my ups in tandem with the inverter, I haven't got the skills to integrate it smoothly or conduct a trial and make electronic mods to counterbalance any issues arising from the possible integration issues of the equipment.
Hence, I shall manually disconnect my mains from the grid in the night time and run the house from the ups using light loads only.

I'll use the 6kva initially, as its nearly ready to use, and I will install the 10kva ups when I get hold of another leaf pack to work with it.

I shall then probably sell on the 6kva ups complete with the 7.5 kWh leaf battery and my own built protection circuitry and equipment.
When do you think you'll be informed with sufficient information to take the plunge and purchase the equipment and start on the installation? I'd love to see a few pics of it when it's installed.

Anthony.
« Last Edit: November 29, 2015, 10:46:37 AM by glyndwr1998 » Logged

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jonesy
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« Reply #66 on: November 28, 2015, 02:09:47 PM »

There are a couple of learned papers on the subject of parallel operation of UPS's etc that use inductors for load balancing god knows what that does to power factors I need to do some reading up.
If you manage a (google) translate I'd be interested in a look.  With the growatt installed, you change the GTI sort of into a controlled supply, so paralleling is possible.  Otherwise a GTI isnt parallelable (is this a word?) It's an all or nothing device. With 2 paralleled, common sync, UPS, even if the load share is unequal, one does not back feed the other. The GTI could still push power into the UPS and reverse it.  Whilst I'd missed the fact that the battery is blocked, this would not necessarily stop the UPS trying to go into charge mode. It will depend how the UPS responds to reverse power.  I've only seen one reference to it on fieldlines (which seems to have been down for a week now) I'm still at a loss as to how the GTI maintains islanding when the powerjack ups is in charge mode; maybe it only checks at start up.
As I'm risk adverse, I'd say a 'normal' ups would not respond well to reverse power, because the internal CT/software won't be looking for it, or worst still will sum the 180 deg import.  
In terms of inductance and PF, I'd say you'd need some pretty enormous ones to affect PF.

This could be done under emergency conditions if there was a CT between the UPS and the 2nd Consumer unit. How to switch between the two is currently exercising my mind as I would need to tap into the UPS's transfer signals, but I don't want to ask questions about the CT's circuitry until the 'non disclosure' agreement is in place.
Could you add a double pole switch to the power transfer switch?
       On the subject of protection; Some of what I have seen so far appals me and even the best is not as good as it could be. BS7671 calls for UPS's to be able to operate distribution circuit protection devices (para 560.6.11). Now if you are feeding a 32amp ring main from a 2KVA UPS then you've got a weasel pee poor design anyway and I agree the breaker probably would not trip.  
A lot of people just do what they always do. You can meet 560.6.11 by fitting a suitable breaker after the UPS.  No discrimination, but that's not necessarily a electrical safety issue.
Using radials as you suggest is sensible and avoids the on/off grid change of protection requirements.

Just thinking out loud, I'm not sure I'd even use the GTI/growatt during a power cut. The ups can handle everything. Plus if there is some unexpected operating between the devices, you could end up trashing the ups & gti, so you lose income when the power returns, pending gti repair. You would lose the FIT on the element 'off grid' - fairly trivial? It's all about the risk of the event happening and the risk of an incident during that period!

I'll have a think about the FMEA. Do you have a starting point of standard terms? I've spent days discussing them only to find a peculiar problem downstream caused by something out of the norm.

« Last Edit: November 28, 2015, 03:57:48 PM by jonesy » Logged

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rogeriko
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« Reply #67 on: November 28, 2015, 09:22:37 PM »

Why all this talk about inneficient UPS's forget them, just use a Sunny Island and everything will work perfectly.
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biff
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« Reply #68 on: November 29, 2015, 12:12:26 AM »

Hi Roger,
      It might be the price and also the desire to recycle. Grin
                                       Biff
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book_woorm
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« Reply #69 on: November 29, 2015, 11:45:34 AM »

Recycling yes. Sunny Island only works with a sunny boy inverter you can't retrofit it to another existing system and apparently it is only compatible with lead acid.
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« Reply #70 on: November 29, 2015, 12:07:03 PM »

Sunny Island can control several different inverters with frequency shifting. It can also control ALL inverters if you use the battery voltage to control dump loads. If the Sunny Island cannot shut down or limit your inverter at least it creates a proper grid and can accept the exess GTI output to charge batteries. Battery voltage can be controlled by switching loads AC or DC. Simple.
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glyndwr1998
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« Reply #71 on: November 29, 2015, 12:48:06 PM »

I for sure haven't considered the sunny island purely down to cost at the moment, it's as simple as that for me.

When the costs come down and more users share their experience with them, how they are operating in real life use terms not brochure terms, how they do integrate with other equipment without comms or teething issues, and their capabilities to utilise lithium battery packs... This is the information that I would like to read.

There is a guy on the photovoltaic forum in Germany that has cuccessfully utilised quite a few Nissan Leaf battery packs with a sunny island, but he also had a sunny boy inverter. He is using them successfully.

I'd like to know how the island communicates with non Sma equipment and how the frequency shifting is set up and controlled.
Thanks.
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rogeriko
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« Reply #72 on: November 29, 2015, 01:33:18 PM »

The Sunny Island gradually increases the grid frequency from 50 to 52 as the batteries are charged. The Sunny Boy sees the increase in frequency and lowers its output accordingly, at 52hz it has cut the output to zero so no problems overcharging the batteries. As soon as a load is turned on the battery voltage drops, frequency changes and the Sunny Boy kicks back in to cover the load. Obviously this can only occur in an off grid situation. Sunny Islands are huge in Germany because the Gov't gives subsidies for battery storage. An interesting document from Enphase describing how to connect their microinverters to an off grid battery system. If your grid tied inverter dosnt support frequency shifting then a dump load setup is required.  Victron inverters could be used as well not just SMA gear.

https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwjox9n_2bXJAhUGORoKHbtGBx4QFggmMAA&url=http%3A%2F%2Fwww2.enphase.com%2Fglobal%2Ffiles%2FEnphase_Application-Note_AC-Coupled-Battery-Based-Systems.pdf&usg=AFQjCNHr2BZQODoZ_itEVP1sIHd6cnO6Cw&sig2=1nsdGFTsZygQ6lQvbYhG9Q&cad=rja
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glyndwr1998
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« Reply #73 on: November 29, 2015, 03:51:25 PM »

Hi roger,

I'm hopeful that in 2 years these sunny islands may have reduced in cost to a level where're becomes practical and affordable to make a judgement call to opt to go over to that system.

I do have sunny boy inverters, I have a sb3800 on an East facing 3.5kw array, and I have a 4000tl with a 4 kW west array, both are grid tied and have consent off dno for a 7.5kw connection. I've also got plans for an additional 3kw utilising a abb 3.6tl inverter, I can't use that to the grid, so have to look at integrating an off grid with that. I've seen a few cheap Chinese hybrid off grid type inverters that look good value but the quality is very questionable that's why a ups is an option at the moment for me as I picked them up at a good keen price, but they are good quality well made reliable units.
Ideal for me at the moment to give me an option in the home if and when a power outage occurs to allow me to continue using the disabled equipment I have at the home like the through floor lift to get my disabled son into his bedroom.
Thanks for your input and help.

Anthony.

« Last Edit: November 29, 2015, 03:53:30 PM by glyndwr1998 » Logged

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book_woorm
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« Reply #74 on: November 29, 2015, 04:31:45 PM »

Hi Rogeriko,
        Interesting what you are saying about Sunny Islands I can understand how frequency shifting would work when islanded. However what happens in a grid connected scheme with Sunny Boy/Sunny island set up. Can the pairing reduce the power you export to nothing and put it in the battery (I'm assuming the battery needs charging). Similarly (when there is capacity in the battery) can it take power from the battery and/or panels and boost the grid supply to the property so you import nothing? The Sunny Island will never raise the frequency in a grid connected system there is just too much inertia and I can't see how it works.

         I rather got put off SMA by the lack of knowledge of the guys they had on their stand at EXCEL a few years ago. I don't want lead acid anyway as I had to sort out a rather frightening experience once with a battery bank that was not as well ventilated as it should have been. I would rather deal with superheated steam than an acid fire.
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2.4 Kw Kyocera Panels (west facing) Feronius inverter; Sonenkraft Solar Thermal with Twin 180Lt & 280 Lt Thermal Stores; SAP 'A' rated property with UFH & wood burner. Full weather compensation on the UFH buffer temperature & differential controller decides where the heat from the wood burner goes.
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