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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Hi Allen,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I’ll try to describe the typical AC
coupled system as well as I can.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>In such a system, a NON-grid tied battery
based inverter (i.e. Magnum MS PAE) is connected as a backup inverter, only
supplying AC power to consumer’s loads when the grid is down. The micro
inverter(s), or string inverters are connected on the load side of the inverters
transfer switch, in parallel with the inverter output so they see AC grid power
(when available) or inverter power when the grid goes down. The micro inverters
/ string inverters in such a system are called AC coupled inverters because the
point of coupling is the AC system rather than the DC system. This allows the battery
based inverter to provide the grid reference to the AC coupled grid-tied
inverters when the utility power is not present – Backup mode. In that
mode the inverter will form the reference for the grid tied inverters and any surplus
power supplied by the grid-tied inverters that is not being consumed by AC
loads will charge the battery of the inverter. In this inverter mode, once
the battery is full, the inverter senses it and shifts the inverter frequency
by .5hz to force the grid tied inverters off, keeping them from exporting
power, thereby stopping the battery from overcharging. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>On a large system, a DC diversion load is
usually added in parallel with the battery to reduce the on/off cycling of the
grid tied inverters, which once the frequency shift happens, will try to
reconnect every five minutes without it. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Using the frequency shift method only is
rather crude, because it essentially is a bang/bang controller – off or
on. Its not a matter of our lack of confidence in the approach, the question is
do you want the battery voltage swinging around by several volts. In a DC
diversion mode system, the surplus energy from the grid tied inverters can be
put to work as a useful dump load rather than just off lining several kw of PV.
<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>We had a white paper describing the AC
couple mode. I’ll see what we can do to make it more widely available,
since the interest in such systems seems to be increasing.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<p class=MsoAutoSig><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'>Brian Faley<o:p></o:p></span></font></p>
<p class=MsoAutoSig><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'>Chief Engineer<o:p></o:p></span></font></p>
<p class=MsoAutoSig><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'>Magnum Energy<o:p></o:p></span></font></p>
<p class=MsoAutoSig><st1:Street w:st="on"><st1:address w:st="on"><font size=3
color=navy face="Times New Roman"><span style='font-size:12.0pt;color:navy'>2111
W Casino Rd</span></font></st1:address></st1:Street><font color=navy><span
style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoAutoSig><st1:place w:st="on"><st1:City w:st="on"><font size=3
color=navy face="Times New Roman"><span style='font-size:12.0pt;color:navy'>Everett</span></font></st1:City><font
color=navy><span style='color:navy'>, <st1:State w:st="on">WA</st1:State> <st1:PostalCode
w:st="on">98204</st1:PostalCode></span></font></st1:place><font color=navy><span
style='color:navy'><o:p></o:p></span></font></p>
<p class=MsoAutoSig><font size=3 color=navy face="Times New Roman"><span
style='font-size:12.0pt;color:navy'>425-353-8833<o:p></o:p></span></font></p>
<p class=MsoAutoSig><st1:PersonName w:st="on"><font size=3 color=navy
face="Times New Roman"><span style='font-size:12.0pt;color:navy'>bfaley@magnumenergy.com</span></font></st1:PersonName><font
color=navy><span style='color:navy'><o:p></o:p></span></font></p>
</div>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div style='border:none;border-left:solid blue 1.5pt;padding:0in 0in 0in 4.0pt'>
<div>
<div class=MsoNormal align=center style='text-align:center'><font size=3
color=black face="Times New Roman"><span style='font-size:12.0pt;color:windowtext'>
<hr size=2 width="100%" align=center tabindex=-1>
</span></font></div>
<p class=MsoNormal><b><font size=2 color=black face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma;color:windowtext;font-weight:bold'>From:</span></font></b><font
size=2 color=black face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;
color:windowtext'> re-wrenches-bounces@lists.re-wrenches.org
[mailto:re-wrenches-bounces@lists.re-wrenches.org] <b><span style='font-weight:
bold'>On Behalf Of </span></b>Allan Sindelar<br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, September 02, 2011
4:45 PM<br>
<b><span style='font-weight:bold'>To:</span></b> RE-wrenches<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [RE-wrenches] AC
Coupling</span></font><font color=black><span style='color:windowtext'><o:p></o:p></span></font></p>
</div>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'>Brian,<br>
Could you speak a bit more to this, please? My understanding is that the need
with a string (or, I suppose, micro-) inverter and a battery-based inverter is
for a way to disconnect full batteries from being overcharged when the grid is
down and sell is disabled. The SMA approach is to shift frequency to reduce
string inverter output. I thought that the battery-based (Outback, Magnum)
approach is to use a contactor to open string inverter AC based on voltage (crude,
but effective). <br>
<br>
So what I understand is that the PAE inverters shift frequency: do you mean it
simulates the shift that a <st1:place w:st="on"><st1:PlaceName w:st="on">Sunny</st1:PlaceName>
<st1:PlaceType w:st="on">Island</st1:PlaceType></st1:place> would do? And if
so, why is a diversion load recommended, and how is it configured into the
system? And where can we read more about how this is designed to work?<br>
Thank you,<br>
Allan<br>
<o:p></o:p></span></font></p>
<div>
<p class=MsoNormal><b><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt;font-weight:bold'>Allan Sindelar</span></font></b><br>
<font size=2><span style='font-size:10.0pt'><a
href="mailto:Allan@positiveenergysolar.com"><font color="#000099"><span
style='color:#000099'>Allan@positiveenergysolar.com</span></font></a></span></font><br>
<font size=2><span style='font-size:10.0pt'>NABCEP Certified Photovoltaic
Installer<br>
NABCEP Certified Technical Sales Professional<br>
<st1:State w:st="on"><st1:place w:st="on">New Mexico</st1:place></st1:State>
EE98J Journeyman Electrician<br>
<b><span style='font-weight:bold'>Positive Energy, Inc.</span></b><br>
3201 Calle Marie<br>
<st1:place w:st="on"><st1:City w:st="on">Santa Fe</st1:City>, <st1:State w:st="on">New
Mexico</st1:State> <st1:PostalCode w:st="on">87507</st1:PostalCode></st1:place><br>
<b><span style='font-weight:bold'>505 424-1112</span></b><br>
<a href="http://www.positiveenergysolar.com/" target="_blank">www.positiveenergysolar.com</a><u1:p></u1:p></span></font>
<o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'><br>
On 9/2/2011 4:39 PM, Brian Faley wrote: <o:p></o:p></span></font></p>
<pre wrap=""><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt'>Hi Larry, <o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Magnum MS PAE inverters do indeed shift the inverter output frequency<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>when the battery is full in order to disconnect grid-tied inverters used<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>in AC coupled systems. It was designed to work in conjunction with a DC<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>diversion load - which is recommended if the system is larger than a<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>couple panels.<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Regards,<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><o:p> </o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Brian Faley<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Chief Engineer<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Magnum Energy<o:p></o:p></span></font></pre><pre><st1:Street
w:st="on"><st1:address w:st="on"><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt'>2111 W Casino Rd</span></font></st1:address></st1:Street><o:p></o:p></pre><pre><st1:place
w:st="on"><st1:City w:st="on"><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt'>Everett</span></font></st1:City>, <st1:State w:st="on">WA</st1:State> <st1:PostalCode
w:st="on">98204</st1:PostalCode></st1:place><o:p></o:p></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>425-353-8833<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'><a
href="mailto:bfaley@magnumenergy.com">bfaley@magnumenergy.com</a><o:p></o:p></span></font></pre></div>
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