[RE-wrenches] AC Coupling

[Mark Frye]

Allen,
 
The other inverters do not simulate the SI. The SI can be paired with a SB
such that there is some degree of proportional control of the SB output
power via frequancy shifts generated by the SI. Consult SMA documentation of
SI operation available on-line at SMA website.
 
Other inverters have a one step frequency shift that will cause most grid
tied inverters to see a line frequecy fault, in turn causing them to go
off-line until the frequecy is corrected.
 
I guess that the folks at Magnum are not totally confident in this setup so
they recommend a back-up safety system which could be either a diversi9on
load or a contactor that disconnects the grid tied inverters all together.
 
Mark Frye 
Berkeley Solar Electric Systems 
303 Redbud Way 
Nevada City,  CA 95959 
(530) 401-8024 
 <http://www.berkeleysolar.com/> www.berkeleysolar.com  
 

  _____  

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Allan
Sindelar
Sent: Friday, September 02, 2011 4:45 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] AC Coupling


Brian,
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). 

So what I understand is that the PAE inverters shift frequency: do you mean
it simulates the shift that a Sunny Island 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?
Thank you,
Allan
 

Allan Sindelar
 <mailto:Allan at positiveenergysolar.com> Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Positive Energy, Inc.
3201 Calle Marie
Santa Fe, New Mexico 87507
505 424-1112
 <http://www.positiveenergysolar.com/> www.positiveenergysolar.com 


On 9/2/2011 4:39 PM, Brian Faley wrote: 

Hi Larry, 

Magnum MS PAE inverters do indeed shift the inverter output frequency

when the battery is full in order to disconnect grid-tied inverters used

in AC coupled systems. It was designed to work in conjunction with a DC

diversion load - which is recommended if the system is larger than a

couple panels.



Regards,



Brian Faley

Chief Engineer

Magnum Energy

2111 W Casino Rd

Everett, WA 98204

425-353-8833

bfaley at magnumenergy.com

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