SMA too sophisticated to be any good?

SpikeandKariSpikeandKari Registered Users Posts: 6 ✭✭
Hi, I'm a newbie here so if I'm posting in the wrong place or using wrong terminology please be gentle!

I have a smallholding in southern Spain and too many orange trees so whilst cutting down half of them I need to pump a lot of water from a borehole to keep the rest of them alive. I considered a solar borehole pump but didn't fancy putting all that money down a hole so voted instead for a standard AC pump and a system to produce lots of activities from solar. I bought a SMA Sunny Boy 3 KW PV inverter which with 3 KW of panels. The AC from this will connect to the output of a Sunny Boy 3 KW battery inverter with 290 AH at 48 V Rolls batteries. The batteries are a little small but the idea is to use the power in the day to pump water with the excess charging the batteries for our house use overnight. Our domestic use is very light. Now the problem. I'm half way through commissioning the system and started with the Sunny Island since the Sunny Boy needs to see AC to fire up. All seemed fine and the Sunny Island inverter fired up but when I tried to connect a generator to charge up the battery bank I kept getting voltage too low error. Now I can monitor the voltage through the SB interface so I see exactly what it is seeing and it is well within spec but after a dozen start ups now still same error.  I then searched on the net and found this dreadful and way overcomplicated document https://www.google.co.uk/url?sa=t&source=web&rct=j&url=http://files.sma.de/dl/15216/SIGEN-11FD1212.pdf&ved=0ahUKEwij6YqN_frMAhWRSxoKHaXyDkEQFggeMAA&usg=AFQjCNE1IwAA-lGRBYX9_bj0IkXaamGZPA&sig2=5YYQBODztcm6AWfChJjclw

Which says at the end many generator companies are unwilling to provide voltage regulation strategies to SMA. I am beginning to think I have made a big mistake. Any of you guys got a generator to work with the Sunny Island and if so what make/model?  Any advice on how to move forward much appreciated. Thanks for looking, Spike

Comments

  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Just a quick question, can you tell us more abuot the generator you have...  size, make, type (invertor or ?), age, fuel etc
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • BB.BB. Super Moderators, Administrators Posts: 31,159 admin
    edited May 2016 #3
    Do you have anyone that can support you at SMA or a local retailer/installer?

    You say AC voltage is within range (possibly +/- 6% of SI setting)? What about AC line frequency from the genset?

    In North America (where we don't usually have SMA "really smart" inverter systems--Sometimes a 100 Watt filament lamp or a small electric heater can be placed as a load on the Genset output--The "base load" supplied by the light can be enough to "stabilize" the genset voltage+frequency enough for the charger (or inverter+charger) to "qualify" the genset.

    The SunnyIsland does seem to be setup for "sharing" a generator+SunnyI inverter running (sort of) in Grid Tied mode. This creates a "local grid" where more SI and (possibly) Gensets can be shared together on one "local or micro grid". This may "limit" your ability to connect any old genset to your SMA SI system.

    The traditional method used on less complex off grid systems is to have the genset either charge the battery bank with a separate AC Battery Charger (and an AC Transfer switch can run AC genset power directly to the loads).

    There is another way where "Inverter-Chargers" can run in "generator support" mode--It is similar in some ways to the SMA setup, but works with "less friendly" AC genset. The inverter charger is "typically" set to have a wider acceptable frequency range (in the USA, 55-65 Hz range to "qualify" a genst is not unusual).

    The SMA system appears to be (default?) set to +/- 2% frequency range (+/- 1.0 Hz for 50 Hz system). That is a pretty tight range for an "average" mechanically speed govern genset.

    The short term fixes is probably to:
    1. Get a separate AC Battery charger compatible with your genset (appropriate Watts/VA rating for genset and battery bank)
    2. Check with SMA and find out if they have a list of "qualified" AC Genset for their SI system
    3. Make a decision to a) keep separate AC battery charger; b) by "SMA qualified" genset; or c) a different inverter+charger brand/model).
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • SpikeandKariSpikeandKari Registered Users Posts: 6 ✭✭
    Hi and thanks for information gentlemen. 
    The genset is a GENERGY Robust series 3 KW rated 2.6 continuous. It uses a standard alternator with electronics for control. It is not an inverter type.. I have had to contact the factory to check that I could tie neutral to earth to comply with the SMA requirement and they were most prompt and helpful. I have not yet asked them about voltage regulation strategies. The genset is new. It shows between 233 and 231 on the front panel and 51 and 52 Hz. I have the SI set up for 230 V 50 Hz I have opened up both voltage and frequency limits in the SB programming for the generator from their defaults to near the widest limits. I can monitor through the SI logged data what it sees from the genset and it matches what I see on the genset front panel. I have added a load to the genset in parallel to the SI and have seen it switch through the genset supply for just a second then the SI throws  an error and resets. The error is always over voltage. I understand that I may have to use a third party charger but it really irks me. I have paid £8K for this kit and connecting a SI to a generator to charge the batteries if there is not enough sun is a basic bit of functionality IMHO. Also 48V chargers here are really expensive and I will need a shunt so the SI can monitor the charging which it can't do itself. I bought the kit from a reputable firm inthe UK, they are supporting me but   when I asked for a generator spec I was told "any modern genset with voltage and frequency in spec".  What I now see from the SMA thoughts on genset requirements which link I posted above indicates that this advice was no good and if I had known how how picky SMA were with genset I would have gone down a Outbacker Victron route. To be frank I really don't understand the difference between a grid and a buzz bar. I have a suspicion that the SI is trying to control the power output of the genset by varying the frequency of the AC which it does when connected to the SB. I would like to ask the genset company what their voltage regulation method is but if I send them the incomprehensible stuff SMA produced and I posted above they will just laugh at me. In the manual set that SMA produced there is of course no mention of genset compatibility requirements. Sorry if I sound P***** Off but I am. Thanks for helping. Spike
  • BB.BB. Super Moderators, Administrators Posts: 31,159 admin
    Spike, I understand your frustration--This is not a science project using somebody else's money--But to power your home.

    There are two basic methods for "paralleling" AC power sources (without using some sort of external control wiring).

    One is "droop voltage" regulation. Basically set the inverter for 230 +/- 6% or 243.8 VAC Hi and 216 VAC low... The SI would "manage" sharing with the genset by raising or lowering the average AC voltage... 230 VAC, the genset would supply 50% of rated output, 244 VAC, 0% of rated genset output, and 216 VAC would be 100% from genset.

    The other way is frequency variation--Say 50 Hz +/- 2%. The SI would output 51 Hz = 0% from genset and 49 Hz would be 100% from genset.

    Can you pick a form of regulation (like droop sharing "on" and frequency sharing "off")?

    Does the genset make any changes in sound when trying to "sync" with the SMA SI? Does the engine turn faster? Does it throttle back? etc....

    Do you have a link to the SMA SI installation/configuration manual with detailed setup instructions? With PID controllers (used for process/temperature/etc. control), there is usually a detailed set of instructions that tell you what each setting does, its range, and how to decide what initial settings you should make).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,559 ✭✭✭✭✭
    edited May 2016 #6
    I just finished a webinar with Schneider and the use SMA for AC coupling of their XW and SW's.
    The short answer here for you is you should not be AC coupling with this small of a system!
    It is a design flaw for you as the designer to try this!
     Sorry but it should be DC coupled and you really need to follow good design practices such as more than 100 AH of battery per 1KW of solar.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Dave are you saying that 100 Ahr / Kw of PV is a  inviolable hard line in the sand for SMA ? He is only 10 Ahr (~3%) short on that formula ...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,559 ✭✭✭✭✭
    No, I really am saying that he should not be AC coupling and as for the battery when people undersize batteries they get problems.
    Break the rules and it all adds up to unintended consequences, especially offgrid where there is no utility to save you!
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • BB.BB. Super Moderators, Administrators Posts: 31,159 admin
    Note, that is 100 ah per 1 kwatt of solar panel on a 48 volt battery bank.

    On a 12 volt bank, that would be 400ah per 1kw of solar panel (and ac inverter rated output).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,559 ✭✭✭✭✭
    And one must also know that they are using the 20Hour rate for the battery capacity spec!
    A very common problem that the inexperienced miss!



    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Yes that is  a pretty small GT setup...  more lead and PV would be better
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • SpikeandKariSpikeandKari Registered Users Posts: 6 ✭✭
    Thanks for your comments. First of all Bill thanks for yours and here is my reply. I have detailed manuals. Part of my problem with SMA is that the information is spread over five separate documents and now with the generator 'expectations' extended to a sixth which is called a 'whitepaper'. I have ploughed through all of them. The only generator performance curve specs are in the 'whitepaper'. I have access to many thresholds and have maxed these out temporarily as an attempt to get past the overvoltage error. Although not explicitly stated I stumbled across mention of a frequency switch to carry out load shedding so at least on the battery inverter to PV inverter side frequency is used to manage power. The generator comes in to the battery inverter on a different connection to the PC inverter but the manual says when the generator is on the output voltage and frequency of the battery inverter is dictated by the genset. There is no option to change power demand scheme.

    Other advice, and thanks too.

    Battery size. I have programmed the C10 level into the unit but since the PVs aren't connected yet and the battery inverter cuts out before using the generator to do any charging  C10 or C20 is a bit moot at the moment IMHO. As for battery capacity my domestic non water pumping demands are very modest and the capacity allows for a five day disconnect, is that not enough? The whole idea was to use the AC predominantly as it is produced to pump water have I really broken some basic design rule here? If I have then why does SMA produce units of this size and specify their use in this way?  If SMA had produced a list of qualified generators or put a genset spec on their technical spec then I would have been forewarned about this problem and gone down a more traditional DC coupled route. Also guys, before the bricks get thrown back, I did post in Beginners Corner so please forgive me for buying kit from a reputable company specified to work in a particular way, reading the manuals, connecting it as specified and then expecting the damn thing to operate. Thanks for your time guys, Mark 
  • mike95490mike95490 Solar Expert Posts: 9,091 ✭✭✭✭✭
    There are way too many generators in various states of repair, SMA could never publish a list.   They could post a build sheet of a working system, and explain how all the parts play together,  
    But making an AC coupled system without a massive battery bank to absorb peak power, will end up being problematic.
    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 ,

  • SpikeandKariSpikeandKari Registered Users Posts: 6 ✭✭
    Just to close this off. An installer visited, found nothing wrong with my installation or the genset but reproduced the overvoltage error from the Sunny Island. We tried an old Mitsubishi 3kw genset that he brought with him so it seems something must be wrong with the waveform on my genset even though on a scope it looked fine. Thanks for your comments

  • mike95490mike95490 Solar Expert Posts: 9,091 ✭✭✭✭✭
    edited June 2016 #15
    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 ,

  • Dave AngeliniDave Angelini Solar Expert Posts: 5,559 ✭✭✭✭✭
    You would need a very sophisticated set-up to capture this on a scope BTW.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • BAElectricBAElectric Registered Users Posts: 2
    I'm having an issue where in my Multicluster 12 Sunny Island 6048 3 phase 208 system.  When my wisperwatt 125k is on to charge the B phase leg will spike an extra 100 amps and is just running its fans and burning heat instead of charging.  there are 4 clusters and they are all acting the same.. the arrow on master and slave 2 point from g -> Batt -> load.. Slave 1 b phase points Gen <- Batt <- load
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,559 ✭✭✭✭✭
    How does it behave without wind?  You then have to isolate a cluster and test. Have you done that?
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

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