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AC COUPLE - PowerPoint PPT Presentation

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AC COUPLE. 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. Before we show how to make AC coupling easy, let’s see just what AC coupling is.

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ac coupled systems
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

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
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
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 inverters1
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 inverters2
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 IslandSince the Sunny Boy output is 240VAC and the Sunny Island input is 120VAC, a step down autoformer is used
SMA Sunny IslandNotice that the output of the SB connects to the output of the SIThe autoformer changes 240V to 120V
SMA Sunny IslandThe 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 CoupledThey 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 didWe 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 comeThe top piece is the autoformerBattery box and cabling is included and drop ships where you want it

sma ac coupled systems
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 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
the grid tie inverter shown can be enphase or any 240vac grid tie up to 4000 watts of actual output
The Grid Tie inverter shown can be Enphase or any 240VAC grid tie up to 4000 watts of actual output
Since the two different inverters have no communication, we install a SSR to knock the grid tie off line as required
uncontrolled battery charging
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 charging1
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 charging2
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 charging3
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 charging4
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
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
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