ac coupled systems growing market segment can be confusing! can be complicated! numerous ways to go...
TRANSCRIPT
AC Coupled Systems
• Growing market segment• Can be confusing!• Can be complicated!• Numerous ways to go• MidNite has taken most of the mystique
out of the equation
One inverter capable of AC
coupling
The SMA Sunny Island is the most difficult inverter to hook up to pass
inspection
More on that later
OutBack inverters were the first to AC couple, but each inverter is only 120VAC• Grid tie
inverters are 240VAC
• 2 inverters required in this setup
It is interesting to note that 90% of this system would be the same for off-grid or battery backed up grid tie.
Can you tell which type this is?
Why AC Couple1. a way to use those expensive grid tie
solar panels during a power outage2. Provides limited power during a power
outage3. Allows the installer to go visit their grid tie
customers with something useful to sell
What is AC Couple• AC Coupling is a controlled back feed to a
battery based inverter• A back feed is hooking up AC to the output
of an inverter• Normally when you back feed an inverter,
they blow up (try it sometime, smile)• AC coupling is a synchronized back feed• The grid tie inverter shifts frequency to
match the battery based inverter before connecting. This makes it ok to do
AC Coupling of inverters
• Battery-less grid tie inverters require a grid to be connected before they will turn on. The grid must meet certain voltage and frequency parameters.
• You have all heard about anti-islanding requirements that the inverters must meet
• Battery based sinewave inverters can meet these requirements
• Inverters do not need to be grid tie listed
AC Coupling of inverters
• Not all battery based sinewave inverters are capable of backfeed.
• Your choices in North America are:• SMA Sunny Island• Outback FX, VFX and Radian• Magnum PAE series• Schneider XW series
AC Coupling of Inverters
• The Sunny Island and Sunny Boy communicate with each other to insure proper battery charging during a power outage.
• No other inverter combination can claim this
SMA Sunny Island
Since the Sunny Boy output is
240VAC and the Sunny Island
input is 120VAC, a step down autoformer is
used
SMA Sunny Island
Notice that the output of the SB connects to the output of the SI
The autoformer changes 240V to
120V
SMA Sunny Island
The SI inverter has only one AC
input. We provide an
optional ATS that5 fits inside
our SMA E-Panel
The Sunny Island/Sunny/
Boy combination was designed to be AC Coupled
They thought of everything
(from a European point
of view)
SMA in Germany still has problems with the US
NEC code. The Sunny Island is
not easy to install to meet
code
SMA had been requesting that MidNite Solar make them an
E-Panel for years. We finally
did
We did not realize how big a deal this was
going to be!
The pre-wired system shown
here is as plug and play as they come
The top piece is the autoformer
Battery box and cabling is included
and drop ships where you want it
SMA AC Coupled systems
• SMA AC Coupled solutions for 1 to 4 inverters
• 4,500 watts to 24,000 watts• Purchase pre-wired and tested or parts• Remember those tech service people we
mentioned? You may need to involve them on your first system.
Enphase AC Coupled systems
• Enphase systems are pretty much the same as all others
• When using a Magnum PAE inverter, you must limit the PV array to less than 4000 watts.
• Failure to do this will result in inverter failure
• Magnum is the easiest for Enphase AC coupling
Since the two different
inverters have no
communication, we install a SSR
to knock the grid tie off line
as required
Uncontrolled battery charging
• Magnum and OutBack inverters charge batteries from AC connected to their outputs
• The inverters sense circuits that control charging are on the AC inputs not the output, therefore cannot control charging
• These inverters charge wide open and cannot taper off.
• A relay is required to disconnect the GT
Uncontrolled battery charging
• SMA has controlled battery charging and tapers off as the batteries get charged
• This requires that the AC coupled system is comprised of a Sunny Island and Sunny Boy. They were designed to work together.
• No external relay required
Uncontrolled battery charging
• Schneider WX shifts frequency to knock the grid tie inverter off line for 5 minutes.
• The XW does this with any brand grid tie inverter, but battery charging does not taper off.
• No external relay required
Uncontrolled battery charging
• OutBack inverters do not taper off like the SMA, nor do they shift frequency like the XW
• You must add an external relay between the grid tie inverter and the battery based inverter
• The OutBack aux output can supply the power & control to drive an external relay
Uncontrolled battery charging
• Magnum inverters do not taper off like the SMA, nor do they shift frequency like the XW
• You must add an external relay between the grid tie inverter and the battery based inverter
• The Magnum router can supply the control to drive an external relay, but not the power
4000 watt limit
• This limit only applies during power outages
• We have another method that allows larger arrays, but reduces the array power during outages
• This is a radical modification, but works
OutBack and Schneider
• 2 OB inverters are required for AC Coupling.
• OB offers superior regulation during outages and has a built in aux circuit
• Schneider offers a good inverter for AC coupling. The XW will shift frequency to knock the GT offline
The MNBCM is very inexpensive ($69 list)It offers at a glance assurance that the
batteries are full.Do not waste your money on a shunt based battery monitor for an AC coupled system.
The batteries are always full.
Three technical support people
• All three will be able to help answer your questions. Ryan, Tom and Kim
• Beware, Kim will try to sell you something