[RE-wrenches] anti islanding?

[Darryl Thayer]

Hi August
I felt I was a little to cryptic in my answer, so here is a longer answer.

 
The inverter always tries to increase the frequency if it is connected to a grid, it could never speed up all those billions of tons of rotating equipment, so the frequency stays the same.  If two inverters see themselves they will both try to increase the frequency, they will succeed and if the frequency is greater than the 60.5 HZ the inverter shuts off.  If there is a load that can stabilize frequency such as a synchronous motor they will either speed up the motor or they will not be able and the motor will slow down.  Either way the frequency changes and the inverter shuts down for frequency out of specification which is <60.5 or >59.3 else the inverter shuts down.  

The inverter also looks at a voltage, and to sell power it wants to raise voltage, necessary to put power into the grid.  Unless the load exactly matches the inverter power the voltage will rise or fall if the load is to large and it will fall out of voltage specification shutting the inverter down.  

One Last feature, the inverter is voltage commutated, and it looks for voltage to add its power to. if you had purely a resistive load, both inverters would wait for the voltage from the other inverter, and nothing would get done.    



Think of it this way, for the system to last for 10 seconds, the speed of this strange device (synchronus motor) cannot change speed more than 0.5% per 10 second and it would coast for 30 minutes before stopping, and this motor would have to be doing no work. 

--- On Sat, 2/13/10, August Goers <august at luminalt.com> wrote:

> From: August Goers <august at luminalt.com>
> Subject: [RE-wrenches]  anti islanding?
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Date: Saturday, February 13, 2010, 10:29 AM
> Hi Wrenches,
> 
> Does anyone know where I can go to read about general
> information on how grid tied inver anti islanding works? I'd
> like to be able to describe this in better detail to our
> tech-savvy clients. 
> 
> Thanks,
> 
> August
> 
> 
> August Goers
> 
> Luminalt Energy Corporation
> O: 415.564.7652
> M: 415.559.1525
> F: 650.244.9167
> www.luminalt.com
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