Single Phase Micro Grid

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BandGap1.1eV

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Long story short, I'm developing a single phase micro grid and have brain damage from all the brick walls I've run into trying to find a solution. I've tried finding a multiport PV/battery inverter but everything on the market is residential sized and will not scale up to the required ~400 kW of PV and 1MWh of battery capacity I need. The one option I found is still in development (6+ months out) but looks promising based on the glossy spec sheet. I also found a smattering of Chinese based options with datasheets in broken english and tech specs that didn't make much sense. I'd rather have a US based supplier so I'm no on call for the next 30 years each time the overseas inverter breaks down.

Option #2 would be to utilize the largest single phase PV inverters I can find (Fronius 15 kW, so far) and then try to find a dedicated battery/grid forming inverter. This search has also proved to be fruitless.

Option #3 involved exploring the use of open delta transformers to allow the use of three phase equipment on my single phase grid but the phase imbalances, harmonics, and kVA losses associated with this configuration quickly ruled it out.

My remaining options involve upgrading the entire single phase grid to a three phase configuration, installing a distributed micrgrid on each residence, or throwing a hail mary in the hopes that someone out there in the ether knows a guy who knows a guy who knows a guy who knows a company that offers a large single phase battery inverter/charger that can be used in a micro grid scenario.

Any takers? 10 internet points available for the first promising response!
 
BandGap1.1eV said:
Long story short, I'm developing a single phase micro grid and have brain damage from all the brick walls I've run into trying to find a solution. I've tried finding a multiport PV/battery inverter but everything on the market is residential sized and will not scale up to the required ~400 kW of PV and 1MWh of battery capacity I need. The one option I found is still in development (6+ months out) but looks promising based on the glossy spec sheet. I also found a smattering of Chinese based options with datasheets in broken english and tech specs that didn't make much sense. I'd rather have a US based supplier so I'm no on call for the next 30 years each time the overseas inverter breaks down.

Option #2 would be to utilize the largest single phase PV inverters I can find (Fronius 15 kW, so far) and then try to find a dedicated battery/grid forming inverter. This search has also proved to be fruitless.

Option #3 involved exploring the use of open delta transformers to allow the use of three phase equipment on my single phase grid but the phase imbalances, harmonics, and kVA losses associated with this configuration quickly ruled it out.

My remaining options involve upgrading the entire single phase grid to a three phase configuration, installing a distributed micrgrid on each residence, or throwing a hail mary in the hopes that someone out there in the ether knows a guy who knows a guy who knows a guy who knows a company that offers a large single phase battery inverter/charger that can be used in a micro grid scenario.

Any takers? 10 internet points available for the first promising response!
Click to expand...

Some help here, perhaps?
https://www.youtube.com/watch?v=rA0msd2ZQWI
 
BandGap1.1eV said:
the required ~400 kW of PV and 1MWh of battery capacity

1 The one option I found is still in development (6+ months out)

2 Option #2 would be to utilize the largest single phase PV inverters I can find (Fronius 15 kW, so far) and then try to find a dedicated battery/grid forming inverter. This search has also proved to be fruitless.

3 Option #3 involved exploring the use of open delta transformers to allow the use of three phase equipment on my single phase grid but the phase imbalances, harmonics, and kVA losses associated with this configuration quickly ruled it out.

#4 upgrading the entire single phase grid to a three phase configuration, installing a distributed micrgrid on each residence,
Click to expand...

Out of curiosity, how many homes are you talking, 80-100?
I'm not following the relation of 400kW of PV to 1MWh of storage.

1 So what's 6 months out in #1?

2 I believe that is the largest single phase inverter. You'd want more than 15kW of battery/grid inverter to go with one. I think you could use say three 6kW battery models, either single or 3 phase.
http://www.bmz-usa.com/files/BMZ_ESS_and_SMA_Sunny_Island_Configuration_Chart.pdf
http://www.bmz-usa.com/files/BMZ_USA_ESS_7_0_Datasheet_12-1-2015.pdf

3 I'm not sure why you'd have to use open delta there?

#4 makes the most sense to me. What's the service voltage? You can't possibly be putting 400kW into the grid using single phase?
14 total 30kW inverters = 420kW.
I believe more than one maker has 480 delta *or* wye for their 30kW models.
I'd connect to the grid at 480V, and step that down to 120/240 or 120/208 depending on what is in the houses, and put step-down xfmrs outside where it makes most sense.
Then put the storage inverters and batteries in the houses.

These aren't the USA versions of things, but there are USA versions.

Edit: 56 total 3000TLs = 168kW, and I can't imagine they'd all be in one place.
They're where they are used- the post office, the one bar on the island, the...Piggeldy Wiggeldy or wherever Tokelau...ians? go probably have 2 or 3, and people homes have 1.
Skip the diesel completely and throw in some wind as far as I'm concerned!

Multicluster Box:
1 x MC-Box-36.3
Sunny Boy:
56 x SB 3000TL
Sunny Island Charger:
32 x SIC50-MPT
Solar power:
260 kWp
Battery inverter power:
156 kW
Available energy per year:
390,000 kWh
Battery storage system:
2,300 kWh
Diesel generator:
60 kW
Autonomous time:
1.5-2 days

Tokelau lies in the South Pacific, north of Samoa. The
territory consists of three atolls that can be reached
only by boat. The previous power supply based on diesel
fuel was expensive and damaging to the environment.
In October 2012, Tokelau became the first place
on earth fully powered by photovoltaics.
The entire system with an output of approximately 1
megawatt is made up of three photovoltaic diesel hybrid
systems (the system described above is an example
of one of three systems).
http://www.sma.de/fileadmin/intersolar/SISystemGuideEN.pdf

ggunn said:
Some help here, perhaps?
Click to expand...

Well at least we can agree about that.
 
Last edited:
"No evidence those large systems are single phase. (Although it's unclear why the OP would feel that single phase is necessary.)" Because its a single phase grid on the island. I know of no way to reliably interconnect a three phase inverter to a single phase grid.

We've discussed the details of this project with Princeton Power, DynaPower, and Pika and the like. All of their products are designed for a three phase grid. They all express interest in helping out, but the Non-Recurring Engineering fees associated with developing the equipment wind up being more expensive than the product they would be selling us.

The one glimmer of hope is a PV/battery inverter from EPC Power out in California, they are the ones who are ~6 months out in terms of production. They make a 150 kW unit that can output single phase 480 (albeit only at ~100 kW)

"Out of curiosity, how many homes are you talking, 80-100?
I'm not following the relation of 400kW of PV to 1MWh of storage."

80 to 100 residences is in the correct ballpark. We've run a few HOMER models and this combination gives us the desired 3-4 days of autonomy without needing to fire the generators to satisfy the load. There is an emergency backup generator on the island that can pickup the whole island, however fuel storage and transport is a big challenge (especially in the winter) which is why we're looking to load up on battery storage (to minimize generator run time) and PV capacity (to pickup the load, and charge the batteries).


Looks like the SMA route is the most promising. It's not ideal (would like to avoid having dozens of inverters to deploy), but seems to be the only real option.

"Um....do I get 20 points?" You get a crisp high-five!

 
BandGap1.1eV said:
~400 kW of PV and 1MWh of battery capacity I need.

Option #2- a dedicated battery/grid forming inverter.

Because its a single phase grid on the island.
I know of no way to reliably interconnect a three phase inverter to a single phase grid.

80 to 100 residences is in the correct ballpark... gives us the desired 3-4 days of autonomy without needing to fire the generators to satisfy the load. There is an emergency backup generator on the island that can pickup the whole island,

Looks like the SMA route is the most promising. It's not ideal (would like to avoid having dozens of inverters to deploy), but seems to be the only real option.
Click to expand...

High five...back at ya! :)

Just to be sure- there's already a single phase grid on the island, and it is not connected to another main (utility) grid?
(Is it 120/208V or 120/240V?)

And the ~400kW of PV panels (if DC) or inverters (if AC) are all in one place?

About option #2- I'm not an engineer (and you are), but this diagram on page 2 ( http://files.sma.de/dl/17107/CLUSTBOX-DUS140330W.pdf ) is showing 2 clusters out of the 4 "two to four three-phase clusters, each with three Sunny Islands, (which) can be connected in parallel."

It's also showing the generator on the left, and the loads on the right.
So the "load" it is showing (as a single 208Y/120V breaker) could be, if using 4 clusters/12 Sunny Islands... 12 houses powered by those 12 SIs?
4 houses on A-B phase, 4 on B-C phase, and 4 on A-C phase?

Page 25 operating manual says ( http://files.sma.de/dl/6966/MC-BOX-6_12-BE-en-20W.pdf )
6.3.1 Connecting the Generator
You can connect a three-phase generator to the Multicluster Box, e.g. a diesel generator or another
grid-forming power generator. However, you also have the option of connecting it to the utility grid....

---
Then for 120/240V...(I think) every house would need one of these ( http://files.sma.de/dl/15892/SMARTFORMER-DUS124616W.pdf ) to make 240V if the house had a single Sunny Island inside (SIs are 120V, takes 2 to make 240V from batteries.)

The same SMA inverters can do both 120/240V split phase or 208Y/120V.
http://files.sma.de/dl/1380/COMMONTXCONFI_AUS161222W.pdf

96 houses? (random guess... but that would make a neat 8 sections of 12 houses each for the "Multicluster"' thing...)

(96) SMA 4548s + (96) SmartFormers
and
(66) SMA 6000TL-US =396kW

One of those BMZ 6.7kWh in each house would = 643kWh of battery...

Hope this is in the ballpark/helps. I'm slightly over 12 dozen there... :)



 
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