3 phase grid tie battery backup

Hi
Im writing from Poland where we have 230 volt ac and 380 volt 3 phase.
Its quite common here for residential houses to be connected on 3 phase.
I'm really struggling because its really hard to find installers here and I wanted to put some solar panels on the roof and set up a grid tie system selling power to the utility company as well as having a battery backup which will automatically run power to the house from the batteries if the grid goes down.
Now I can see that Outback does a gfx and Xantrex an xw and a firm called Sunways in Germany supplies a 3 phase box grid tie in one box (nt8000)but no battery backup. Although I can find lots of pretty pictures of single phase systems I cant find anything on 3 phase. Also whats annoying me is that it seems I need 3 inverters to do the job .I was offered here a setup with 3 sunny Island 5048 and 3 sunny Boy inverters and 20 solar panels and 24 batteries.
Now I dont want to light up Poland just switch on a few lights and keep the gas boiler running if the grid goes down.
Does the Outback and the xantrex system also require 3 inverters wired together ?
Is there any reasonable priced simple solution to this problem ?
Appreciate any advice
tks

Comments

  • mradtkemradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: 3 phase grid tie battery backup

    Hello tks,

    Where do you live in Poland? I've visited several times and I think that Poland is a beautiful country with wonderful people.

    I too have 3 phase power in the USA. However, I don't have a battery backup PV system, just grid tie. In my case, I just feed one phase with the inverter and the power company is happy with that.

    What do you use the 3 phases for? I only use my 3 phase power for the air conditioning. If you use the 3 phase service only for non-essential purposes, perhaps you can build your system as a single phase battery backup in the conventional way, including a single phase transfer switch. That way, you are grid tied in a similar way that I am for normal operation. When the power fails, the transfer switch disconnects from the mains and one of your local phases continues to run from the battery backup. If your boiler and a few lights are on that phase, things should be fine as long as no 3 phase equipment is used.

    Mike
  • System2System2 Posts: 6,290 admin
    Re: 3 phase grid tie battery backup

    Hello Mike
    That is excellent information and dont laugh but I have probably spent 15 hours on the internet just trying to find what you just said.
    I live not far from Kielce about couple of hours south of Warsaw.
    I will try and find out if it could be acceptable to be grid tied here while feeding just one phase in. This is not the good old free thinking usa I'm afraid specially when it comes to local authorities.
    No I have nothing that runs permanently on 3 phase . The only thing 3 phase is my electric arc welder which I use about once every 5 years !The house is wired so that say the lights upstairs run on on phase or the sockets on another phase and lights on another floor on another phase and so on. No 3 phase appliances .
    Now if I go for selling into the grid via one phase and backing up one phase with batteries I guess I would have to do both the backup and sell to a particular one of the phases since occasionally just one phase goes down here and the other two are still working ?Is that the safest setup ?
    Regarding suitable models I have not seen Xantrex or Outback power anywhere on sale here but am pleased to say I noticed someone who seems to be selling models of Studer which I think is a swiss company selling pure sinewave machines with backup and it looks like a serious company. Otherwise there are sunny islands and sunny boys on offer but have not seen anything else.
    Please let me know if you have any thoughts on these models for what I need to do.
    Many thanks again for the tip
  • mradtkemradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: 3 phase grid tie battery backup

    tks,

    I have very little PV experience. I just happened to notice that you had 3 phase power and that was one of my concerns when I installed my system. You may have read my long chain in this forum about my Fronius problem and know that I am an engineer. But, I spent most of my career in software, so about the only engineering skill that I can bring to this discussion is logical thought. You seem very good at that already.

    Since you have no permanent 3 phase loads, I see only the same issues that you already have identified. Perhaps I can restate them:

    1) Will the power company agree to back feeding a single phase?

    2) Do your local building codes allow for a transfer switch and emergency power on a single phase?

    3) Can you choose a phase that will satisfy your emergency power needs? If not, can you rewire some of your home to meet that requirement?

    I think that if you can answer yes to all 3 of those questions, there will be nothing special about using any inverter that is capable of grid tie / battery backup.

    My inverter experience is limited to my own grid tie system and Fronius problems. However, others on this forum have broad experience and can help you choose among brands and models that may be available to you. I am looking forward to hearing what they have to say as well.

    Mike
  • BB.BB. Super Moderators Posts: 26,867 admin
    Re: 3 phase grid tie battery backup

    mradtke,

    Don't disagree with anything you said.

    Regarding emergency backup--presumably, you could use an inverter with an internal transfer switch for each independent phase... 1, 2, or even 3 inverters. And, each will fail-over to backup upon its own phase failing... So, it would be possible for phases A and B to be powered by the utility and Phase C would be running from the inverter.

    Depending on how your home is wired--this may, or may not, be a problem.

    In the US, we have both "Delta" ("triangle") and "Y" type 3 phase available. And for 120 VAC power, we use a common or Center Tap to carry the lower voltage current. (also done for split phase 240/120 VAC home circuits too).

    But, when all of the phases are "in phase"--that common line will never carry more current that the maximum for one of the phases... If you have three independent loads, the currents add up and the common current return line is "zero" amps.

    But, if you have three independent inverters using a common return (or sharing a common phase return)--because they are not in "synchronization" you could end up with excessive current in common lines...

    If you have a two pole transfer switch that 100% isolates the protected loads from the AC Mains--I don't think single phase inverters will be a problem. However, you would probably need to add a sub-panel off of each inverter to fuse/breaker the downstream distribution circuits (depending on the size of the inverters and downstream loads).

    I have no clue as to how your home is wired for 3 phase power--I assume that you (or your electrician) will need to understand the issues of running, up to three, un-synchronized inverters to power your home as backup power. Obviously, will not run a 3 phase motor.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: 3 phase grid tie battery backup

    Hi
    Thanks for both your replies.
    I just spent about half an hour doing a detailed reply and lost it.
    Its half past 2 in the morning here and I've got to sleep so will have another go tomorrow.
    Meanwhile here is what looks to me some nice diagrams and setups from the Studer company in a pdf file
    http://www.studer-inno.com/fileadmin/studer/uploads/Application_notes/AN003_Anti-blackout_system_for_grid_connected_solar_installations__Solsafe_concept_.pdf

    As there are no 3 phase appliances running in the house here .Each of the 3 phases is used for a different room or different set of lights in a different room. The 3 phase wiring is carried up to a fuse box on each floor and then a cable carrying live neutral and earth of a particular phase is run from the fuse box on each floor to say a wall socket and then on to the next socket. Each fuse box is carefully labelled showing which fuse carries which set of lights or sockets and which phase is supplying them. It would be easy for an electrician to resort the wiring so that all the important things to back up were on one particular phase.
    I am not an electrician so I dont know if its triangle or y. I know that three live wires plus neutral and earth come into the house and that neutral is connected to earth where they come in.
    Regarding balancing I thought xantrex outback and sma did ranges which worked on 3 phase but required 3 inverters to do it. But I'm not clear what else I would need to have this and backup too. Anyway I think if I could only go down the road of having 3 inverters it would seem a bit excessive for my requirement.
    This 3 phase grid tied inverter from sunways looks nice but no suggestion of any backup to go with it
    http://www.sunways.de/en/products/solarinverter/Solar_Inverter_NT10000/index.php
    I have contacted a solar installer here to ask about selling and backing up one phase and will post if I can gey a reply to that.
    I have also asked this question to Studer but no answer yet.
    I will try and read your post on the fronius problem as it might help me to learn about solar setup.
    I would be interested to hear what you think of the Studer document
    Thanks again
  • crewzercrewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: 3 phase grid tie battery backup

    tks,

    OutBack's grid-interactive inverters ("G" models) are only available for 120 VAC / 60 Hz (single phase) or 120/240 VAC / 60 Hz (dual phase) applications. In general, these inverters are only suitable for the North American market.

    Our 230 VAC / 50 Hz inverters can be stacked for 3-phase, but they are for off-grid-, backup-, or hybrid applications only. They cannot "sell" back to the grid. They can, however, reduce grid energy use and provide backup power if connected to a PV array via a charge controller.

    The largest "stack" size is three inverters (one per phase) for a total power rating of 9 kVA. Please see: http://www.outbackpower.com/products/sinewave_inverter/international/

    The attached drawing illustrates a single phase "hybrid" solution. Please feel free to contact me with any other questions.

    Regards,

    Jim Goodnight
    "crewzer"
    Eastern Regional Sales Manager (U.S.)
    OutBack Power Systems
  • blackswan555blackswan555 Solar Expert Posts: 246 ✭✭✭✭✭
    Re: 3 phase grid tie battery backup

    Hi from Spain, we have similar wiring and connection methods, You could use a single 1ph inverter and a 3 ph ac transfer switch, link the 3 ph`s on the inv side of the switch, maybe need to monitor/switch on phase loss, would depend on your grid providers specifications if you could sell,
    Which if also similar to Spain is the big point, Check what they want first, Here we are allowed grid tie, off grid and only battery-less sell to grid, two very different systems for us,
    Basically; sell to grid is a high voltage 380v string, > inverter > special utility meter, no use of generated electricity by yourselves, we get 3 x retail price :D eg 33c at the mo ( was 4 x :roll:)
    Grid tie, Panels generate enough to power the house and fully charge the batteries in day time, batteries run house at night, utility kicks in to charge batteries only if no sun for extended period of time, But I would say the choice of which route to go rests with your utility :D
    Have a good one
    Tim
  • mradtkemradtke Solar Expert Posts: 53 ✭✭✭✭
    Re: 3 phase grid tie battery backup

    Hello,

    Tim made a good point that if a transfer switch was available that paralleled the 3 phases in your home when you were on local power, you would not have to choose which phase to keep alive. If such a switch were available, it still must be acceptable for local regulations. It retains the restriction on not having any active 3 phase loads.

    I followed your link to the Solsafe. I have no knowledge of how the usual grid tie / battery backup systems work, but the Solsafe documentation implies that their design is not standard practice since it separates the PV system from the battery backup system.

    Two things that I noticed:

    1) I don't think that the information on the 3 phase connection brings anything new to the discussion. The diagram looks simple, but please note the every wire that is marked with a /// is actually three wires and the 3 phase system that results is actually 3 single phase systems.

    2) The Solsafe schematics show wiring for separate meters for incoming and outgoing power. In the USA, this usually a single bi-directional billing meter. I haven't tried to sort out how to wire the Solsafe in the USA manner, but it looks like it would be straight forward. Of course, I have no idea what your local rules are.

    Now the bad news. I see two related problems that are the result of the Solsafe system using the PV inverter to power local loads as well as the grid:

    a) When on backup power with the PV inverter operating, the local load must be greater than the PV power being supplied. If not, the local voltage will go to high and the PV inverter will do a safety shutdown.

    b) The Solsafe documentation requests that the “impedance jumps” feature of the PV inverter be disabled. This is a grid safety feature which is probably required by your local regulations.

    In summary, I am not comfortable with the Solsafe concept.

    Mike
  • BB.BB. Super Moderators Posts: 26,867 admin
    Re: 3 phase grid tie battery backup

    The SolSafe does throw in one extra relay that allows it to "turn off" the GT Inverter once the battery bank is "full"... So--at least from a first pass look through the system, it appears to meet the requirements of being able to tie a GT inverter + Off-Grid inverter together and control it appropriately.

    Further issues--Not sure how they phase sync the Off-Grid inverters (perhaps the models they use have 3 phase sync--was not called out on the diagram, and I have not researched all of the components).

    Failure modes and local certifications--I don't know what requirements they meet, or what the local requirements would be.

    It appears to have all of the basic functions needed for building a hybrid 3 phase (or single phase) inverter system using a high voltage Solar PV Powered GT Inverter--something that we have not seen before in a single off-the-shelf package.

    Looks very interesting (is it cost effective and legal???).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • System2System2 Posts: 6,290 admin
    Re: 3 phase grid tie battery backup

    Thankyou for all your replies.
    No reply yet from the solar installer here so I cannot update on any regulations here yet. Im starting to wonder if the installer here knows what the regulations are. Anyway I will perservere.
    Interesting from spain idea and also interesting that battery backup not allowed on grid connected systems there.
    Also interested to note that Outback power does not do a grid connected model for Europe.
    To mdadtke yes I am not very good at this stuff but even I was staring at the diagram and wondering if the inverter would switch off if the battery power dropped a bit since most of the inverters would be monitoring for a grid voltage.
    I'm afraid I only started looking at this whole solar idea a few weeks ago and at the moment there is too much for me to take in . So I have to continue reading and understanding the way these things go together and following posts on this board. I should really be in the beginners corner.
    Regarding the question of whether this Studer sytem is cost effective I am starting to have a few small doubts .I only picked up some prices by trawling around on other sites. Also despite staring at the diagrams I have not worked out how many bits and pieces are needed to put it together. It looks like a solar inverter is needed for a start (say 1000 dlrs) then the studer xtender box another 2000 dlrs then this solsafe box even worse 3000 dlrs.
    There is one other quite odd concept also coming from Studer which I missed while I was pondering over the "solsafe " I noticed that inside their Xtender inverter they also have something called "smart boost" which if I understand the diagrams/description correctly allows their inverter to be connected to the grid but not selling to the grid. But the smart boost is monitoring the currents coming form the solar panels and the battery backup whilst also monitoring the grid current and is able to reduce the incoming grid current if the solar/battery energy is available and send it to the house. So although its not a grid connect in the sense it is crediting a meter it is actually while still being connected to the grid able to use the solar energy rather than the grid energy and is not just charging up the batteries.
    Here is a description of the smart boost function and diagrams.

    http://studer-inno.com/fileadmin/studer/uploads/Application_notes/AN002_Renewable_energy_system_connected_to_a_grid_without_grid_feeding.pdf

    Maybe I got the wrong end of the stick ?
    Is this also something new ?
    I'm on a steep learning curve here but thanks for all your comments which are helping me to go forwards !
  • BB.BB. Super Moderators Posts: 26,867 admin
    Re: 3 phase grid tie battery backup

    Using the Grid Tied inverter to both power the grid and charge the batteries through a True Sine Wave Off-Grid inverter by "Back Feeding" energy through the Off-Grid TSW Inverter is a relatively new concept (at least, we have only been discussing it for around a couple years).

    This "process" is nice for us in the "US" because many of us have GT inverter systems, but would like to run our solar panels into an Off-Grid inverter when we have a power failure.

    However, GT inverters typically have an input voltage of 200-600 VDC, and the off-grid solar charge controllers (to charge the battery bank) only work from Vbank to ~140 VDC.... So, there is no easy way to "plug" the solar panels into a battery bank charge controller without going through the GT to Off-grid inverter connections.

    So the Studer "GT / Off Grid / Mains controller" could be a nice "turnkey" solution for those of us that would like to do the GT+Off Grid inverter solution (if it safe).

    The Smart Boost is exactly what you think it is... For those places where the utility will not allow "Net Metered" Grid Tie solar inverters (the inverter can actually push energy back out to the grid and turn the meter backwards)... This one simple allows the inverter to replace some of the mains power with solar power for down stream loads (and stop the power meter from turning--and legally saving money).

    Also, a very nice solution for many places in the US where Grid Tied net metering is not allowed by law/utility.

    Sounds like a very cool engineering driven company filling niches in solar power. Now--can they make money doing it and is it cost effective for the home owner?

    One drawback is that unless you have a "large and steady" load--there may be lots of time during the day when you have solar power available, but no AC load to drive--so you are wasting your solar power (that you paid to install, but are not benefiting). May make sense if you have continuous loads (swimming pool pump, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • blackswan555blackswan555 Solar Expert Posts: 246 ✭✭✭✭✭
    Re: 3 phase grid tie battery backup

    Battery back-up / Grid tie is allowed, Just not if you want to sell to grid, If you want to sell, the system must be battery-less,
    Maybe cause we get 3 x retail price for selling back, Of course no one would ever think to charge them at night and bump the next days solar lol:D but probably more to do with the safety of the linesmen.
    Have a good one
    Tim
  • System2System2 Posts: 6,290 admin
    Re: 3 phase grid tie battery backup

    Thankyou for your replies.
    It remains for me now to do a little more research about what is likely to be allowed to be installed here.
    Also if there are any guidelines about what amount of credit is returned on power sold back on grid tied applications.
    It may take some time but I will post back if I can get some more information on this subject.
    I also need to read through BB's post a few times and convince myself that I understand it .
    Incedentally I contacted Xantrex and asked them if it was possible to sell back into the grid into one phase of my 3 phase supply using a xantrex xw. They replied as follows :-

    "You cannot back up and sell back just one phase. For 3 phases system, you need at least 3 XW. one XW per phase.
    Besides XW, solar panels and batteries, you need solar charger controller which is installed between solar panels and batteries to charge batteries from solar power. Solar panels cannot connect to XW directly."

    So I am pondering over that reply too at the moment.
    Best wishes and thanks again
  • BB.BB. Super Moderators Posts: 26,867 admin
    Re: 3 phase grid tie battery backup

    Yes, the XW system is a battery powered inverter... You have to connect the solar panels through normal MPPT Charge Controllers (as if this was an off-grid battery charging system).

    The XW inverter, as I understand, in GT mode monitors the charge voltage on the battery--as as they are at the programmed bank voltage level (absorb or float?--I don't understand the transition to grid sell--I have not read any manuals at this time for the XW) then the XW starts to sell power to the grid.

    The XW also, as I remember, contains its own internal AC to Battery charger--can work with grid or generator backup power.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 7,307 ✭✭✭✭
    Re: 3 phase grid tie battery backup

    You could use a single XW, and a 3 phase transformer with a seperate 3phase auto-transfer switch. How much solar PV are you planning to install ?
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Solar GuppySolar Guppy Solar Expert Posts: 1,959 ✭✭✭
    Re: 3 phase grid tie battery backup
    BB. wrote: »
    Yes, the XW system is a battery powered inverter... You have to connect the solar panels through normal MPPT Charge Controllers (as if this was an off-grid battery charging system).

    The XW inverter, as I understand, in GT mode monitors the charge voltage on the battery--as as they are at the programmed bank voltage level (absorb or float?--I don't understand the transition to grid sell--I have not read any manuals at this time for the XW) then the XW starts to sell power to the grid.

    The XW also, as I remember, contains its own internal AC to Battery charger--can work with grid or generator backup power.

    -Bill

    The XW has a configuration screen for the Sell to Grid, options include battery sell voltage and sell amps. So if one selects say 52V, if anything is putting energy into the battery pack and it raises above the 52V, then the XW sends that energy back out its AC input 1 in a Grid tie fashion meeting UL1741 specs ( 52V is just an example, totally user selectable )
  • System2System2 Posts: 6,290 admin
    Re: 3 phase grid tie battery backup

    Thanks for replies.
    Hmmm I'm not sure how many pv panels I will install yet as I am still studying it.
    I guess this is a case of dipping my toe in the water first.
    My original idea was about 5 solar panels totaling about a kilowat.
    Then to sell into the grid and back up one of the phases with a couple of meaty batteries.
    If I actually got this far and a light came on during a power failure and there was even some sort of sign of a credit on the meter I would pick myself off the ground and plan the next move.
    I'm not sure what to make of the xantrex replies.
    Solar guppy is indicating that the xw will feed into the grid from a battery backup into one of the phases. Presumably in the same way as it would into 3 of the phases with 3 xw's
    So I wonder if the reply Xantrex gave me that one xw cant be used has to do with something else.
    regards
  • BB.BB. Super Moderators Posts: 26,867 admin
    Re: 3 phase grid tie battery backup

    At least on the US Website, the XW system is only 120/240 VAC 60Hz...

    I guess the new UL rules require the units to sense 120 VAC, and are you not 50Hz? Between those two requirements--the North American unit would not work on your power (single or three phase).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Solar GuppySolar Guppy Solar Expert Posts: 1,959 ✭✭✭
    Re: 3 phase grid tie battery backup

    I was replying to how GT works, not that it could work in non US/CA area's

    The XW is only 60hz 240 split phase and UL1741 now requires the monitoring of the balance to the neutral wire for gridTie applications. Germany by far has the most manufactures of GridTie inverters, something like 70+ manufactures I was once told so I would suggest you work closer to where you live to find solutions
  • System2System2 Posts: 6,290 admin
    Re: 3 phase grid tie battery backup

    outside of the usa any sale of a xantrex xw on 230vac 50hz certainly is elusive which is why I contacted xantrex.
    I notice this guy in hudson usa is selling one

    http://store.altenergystore.com/Inverters/Export-Inverters-230V-50Hz/Xantrex-XW4548-230-50-European-InverterCharger/p6980/

    But I cant imagine who to.

    Apart from Studer and maybe xantrex I havent come across any manufacturer of european models of stand alone grid tied inverter with in built battery backup
    Anyway like you say time to close this post and find a european board that deals in 230/380 volt 50hz
    Thankyou for the earlier answers which regardless of voltage I found to be extremely helpful
  • BB.BB. Super Moderators Posts: 26,867 admin
    Re: 3 phase grid tie battery backup

    Trebor,

    Please feel free to post anything you find here... We are always interested in learning new things.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • blackswan555blackswan555 Solar Expert Posts: 246 ✭✭✭✭✭
    Re: 3 phase grid tie battery backup

    Trebor, the inverter in your link is similar to the others,(outback etc) you still need multiple units for 3 ph, and it is not sell to grid.
    Have a good one
    Tim
  • System2System2 Posts: 6,290 admin
    Re: 3 phase grid tie battery backup

    OK
    Thanks a lot
    I will be in touch soon as I can rustle together a working plan.
    Might have to use a bit of blackswans silver crossee palm idea around here to get some action.
    Still bloddy snowing here
    regards
  • System2System2 Posts: 6,290 admin
    Re: 3 phase grid tie battery backup

    I have a house running on the grid in two phases 240 volt each. I have a power supply by Hydro
    What is the best way to get electricity to the grid for the two phases?
    Do I need two generators and two grid interactive inverters?
    Or do I need a three phase Grid intractive inverter and dump one phase?
    Or is there a better way?
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: 3 phase grid tie battery backup

    gordon,
    i am guessing you are referring to the standard 3 wire 240vac system most homes have. some inverters can make use of a transformer to up the voltage to the 240vac area. an inverter like the xw series from xantrex makes either 120vac or 240vac built into the unit.
    one generator would do fine, but why would you sell power to the grid when it'll cost you more to produce it(and is from a fossil fuel source) than what they will give you for it? many ask for the break even point on solar and often complain of how long it is, but there isn't a breakeven point with fossil fuels.
    or was this an april fools question?;):D:p
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