Homebrewed Electricity > Controls
Demonstration of Generator Support
ChrisOlson:
--- Quote from: thankful on October 29, 2013, 08:04:03 PM ---Does anyone have the latest skinny on what inverters do a good/bad job with Generator Support?
--- End quote ---
That video got deleted off my YouTube Channel. It was done with a Xantrex SW Plus 5548. Since I made that video we have a new Schneider Electric Conext XW Power System with ComBox monitoring, logging and remote system control
The Trace SW-series, Xantrex SW Plus-series, Xantrex (now Schneider Conext) XW and SW-series all do excellent generator support, and have for 20 years.
The Outback GS8048 Radian is supposed to have it - I spent most of one afternoon at a neighbor's place trying to get it to work. Never could make it work right. All they did in the Radian was re-label "Grid Support" for grid-tie applications to "Generator Support" on AC2 input. It's a hack and keeping the generator qualified on it is damned near impossible. In trying to get the Radian system that I worked on to work with it, it became evident in talking with Outback tech support, and in the design of the hardware, that they do not have a single clue what they are doing when it comes to getting generators to interact with an off-grid inverter system. I finally gave up on it and decided at the end of the day that the GS8048 was designed for grid-tie, not off-grid. Plus the Mate3 is the most convoluted mess I have ever seen in my life - actually worse than the Mate and Mate2 (I never believed that was possible).
The Outback GFX is advertised as having generator support. I only know of one person who has tried it and said they got it to work with a Honda EU2000 inverter generator.
None of the other Outback inverters have it. Some people claim you can get a GVFX-series grid-tie inverter to do it with an inverter generator acting as the "grid". Outback tech support says it is not supported in the GVFX-series, and in fact they don't even support a GVFX for off-grid use at ALL.
The Magnum MSH4024RE has generator support and is now released for sale. I have no experience with the Magnum, so can't tell you if it works or not. None of the other Magnum inverters have it.
The SMA Sunny Island has generator support. Also have no experience with them, so can't vouch for it.
The bottom line is that if you design your system to use it for peak load management, and have a decent sized system, there is only one inverter that you can buy with 100% knowledge that it will work, is fully supported by tech support, and works out-of-the-box even with generators with high THD and freq and voltage out of range - and that is the Schneider XW-series.
The XW-series inverters are split-phase for the North American market. Getting gen support to work with a split phase system where you can have leg imbalances of up to 75% between L1 and L2, and having it work every single time, is no small feat. Gen support is easy on single phase 120V output inverters. Not so easy on split-phase. The engineers at Xantrex (now owned by Schneider Electric) have years of experience with it, plus they know and understand why off-grid people use it. So the Conext XW and SW-series is the only one I can recommend if you want it to "just work".
--
Chris
kitestrings:
Hey Chris,
Now that you've had the Conext equipment awhile (couple years?), I was curious if your opinion/experience has changed much (for better or worse, or just what you expected)... other features you like, hate or have learned to live with maybe.
I was looking at their specs a bit. Had a couple questions. Not that I'm rushing out to by anything, just curious mostly:
It looks like the 4 kW unit is 24V, and maybe is only available at this input voltage. Is that right? I wondered why not 48V (which I'd thought was your nominal bank) as many offer.
Does your aux generator synch up pretty well, and does it ever not? I was wondering what happens if the generator has any sort of problems (governor problems, iced-up intake, rats-nest in air filter, you run out of fuel). I assume there are frequency and voltage parameters, outside of which it doesn't connect and contribute.
The standby load losses seem high. 40 watts?
Regards, ~kitestrings
ChrisOlson:
The equipment is fantastic. It is so dead reliable, and so much like having utility power, that we don't even think about it anymore. No flickering in the lights when the A/C compressor kicks in (yes, we even run a 1.5 ton central A/C unit with it), it will handle significant overload for quite awhile, has no de-rating based on temp, and the entire system (solar controllers, inverter, AGS, ComBox, SCP) integrates better than anything else I've ever seen or worked with.
The 24V unit is only available as 4.0 kVA. The comparable 48V unit (XW4548) has a few more watts capacity and is the same price as the 4024. I suspect they don't offer a 4.0 kVA 48V unit because of the 4548.
You can set the allowable voltage and frequency limits for your genset, and get the XW to sync up with it. BUT that "dirty" power is passed on to your loads too. So it pays to buy a decent generator. If the genset is operating and it falls outside the allowable voltage and freq that you have set, the XW will disqualify and take over. Then it will analyze whether or not the generator is stable enough to re-sync with it. If the genset is operating in allowable limits, no load, the XW will re-sync with it and load it according to what you have the Gen Support level set to. But if there's a rat's nest plugging the air filter, within milliseconds it will "spit" the genset off and take over again. It will continue to try this several times (I think six) and if the genset don't straighten out and play decent the XW will shut it down (assuming it is controlled by the AGS) and flash a warning (red light) with a message on the SCP telling you that the genset is no good and you need to fix it. If you have a ComBox it also sends an email to your cell phone telling you that the genset is fricked up and it disabled further auto-starting of it until you get around to fixing it.
The XW is a big transformer-based inverter. Just the transformer in it weighs about 65 lbs - more than a whole Outback FX-series, or Magnum PAE, inverter. Big transformers like that eat up quite a bit of power when idle because there's a lot of copper in it. But that copper mass is also why it can handle significant overloads for a long time, and why it has such rock stable power output. Ideal loading is 20% rated continuous capacity or better. So if you buy one and your normal loads are only 500-600 watts don't buy a 6048. Buy the smaller one. The smaller one will still handle your biggest loads using gen support, and be more efficient for the >90% of the time that your loads are at baseline.
The thing I like about it is that my wife can be doing laundry with the washer and electric clothes dryer going, decide to make a pizza in the oven (electric range) and turn that on, the well pump can kick in, and the inverter still handles all this, along with all the other stuff going, even though it is grossly overloaded. It waits for one minute and if something don't get turned off it fires up the gen, warms it up and syncs with it, and transfers 4.0 kVA of the load the genset to reduce the load on the inverter back below rated continous. It is so seamless that we do not even think twice about it anymore.
So overall I consider the big XW to be pretty much the "Cadillac" of off-grid power. It is a proven design that has been around for many years, they rarely break, Schneider Electric now has a tech support dept that far outshines anything Xantrex ever had, and the integration of the system components has not been matched by anybody else. I am extremely pleased with it and not a single complaint because the XW has basically given us utility-scale (and quality) power in an off-grid situation. And it does it without having to stack inverters, and buy a lot of extra batteries to power stacked inverters.
I put the pencil to it long ago and genset fuel for when you need overload capacity is less than 30% of the cost, long term, that JUST the extra batteries would cost to power stacked inverters at the same capacity as the XW+Genset during gen support operation. The longest I have ever seen the genset run (logged by our ComBox) is 3 hours 53 minutes one time on gen support. And that was for Christmas when my wife had EVERYTHING in the house fired up to cook Christmas dinner for the whole family that was there and using a totally electric kitchen to do it. So the genset burns about .65 gal/hr at that load and we used 2.6 gallons of gas that cost like $10 bucks. Big whoop, ya' know? If you look at it realistically, you could spend $4 Grand on more batteries, and $3,600 on another inverter to power all that. But what is the chances that you can recharge those batteries on RE power later? Nil to none. We used something like 32 kWh in that four hours, and even with all the expense in extra batteries and another inverter, there is a greater than 95% chance the genset would still still start to charge batteries.
And in a nutshell, that is why I designed our system to use gen support as an integral part of it.
kitestrings:
Thanks for the update. Sounds like a great system, and the concept makes perfect sense.
Our electrical loads are much lighter, but we rely more on LP than I'd like to; plan to. At ~$45/MMBtu that's not the deal your dad got for hunting camp anymore. A lot of folks are off-grid but they've only traded utilities.
How, or do, your Classics integrate with the Combox? Oh, and what's the AGS, auto gen start maybe?
~ks
ChrisOlson:
--- Quote from: kitestrings on June 03, 2014, 08:56:35 PM ---Our electrical loads are much lighter, but we rely more on LP than I'd like to; plan to. At ~$45/MMBtu that's not the deal your dad got for hunting camp anymore. A lot of folks are off-grid but they've only traded utilities.
--- End quote ---
We burn gasoline and diesel fuel in our generators. But we didn't end up off-grid to prove a point about "going green", reducing our carbon footprint, or saving the planet or anything like that. Some folks think it's a sin to run a generator off-grid, while they cook on a propane stove. Well, we don't look at it that way. For us it's all about economics, efficiency and convenience.
--- Quote ---How, or do, your Classics integrate with the Combox? Oh, and what's the AGS, auto gen start maybe?
--- End quote ---
The Classics do not integrate at all. They are pretty much standalone. The XW system is always in sync. There is a hierarchy of sorts on Xanbus that determines certain things, such as which component is the primary charger for instance. If there is solar power available, then MPPT1 becomes the primary charger and all other components in the system that can charge batteries (inverter included) follow it from bulk to absorb to float, etc.. If there is no solar power available, then inverter #1 becomes the primary charger (assuming a situation with more than one inverter). You don't have to set this - it's totally automatic.
If you want to change the setting for Absorb V, for instance, you only have to change it in one thing - the change is automatically made on the other components in the system that can charge batteries and use that setting. It is called "cascading" the settings over Xanbus. So you don't have to change it manually in every component.
During charging with the MPPT controllers, instead of each controller showing their individual output on their screens, it shows the total System Output to the battery in watts and amps. So you don't have to stand there and add up what each controller is outputting to figure out what your system is producing. Although you can have each controller show their individual output too.
These are just some examples that are really the tip of the iceberg on how the XW System is a total integrated power system.
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