[RE-wrenches] Hawaii Frequency Settings

[Dave Click]

That's correct, it's a 57.0 - 60.5 Hz operating window.

http://www.heco.com/portal/site/heco/menuitem.508576f78baa14340b4c0610c510b1ca/?vgnextoid=12a290a2decab110VgnVCM1000005c011bacRCRD&cpsextcurrchannel=1#bk6

According to that website, the requirement only applied to systems 
interconnected after 2011/12/23 (maybe someone was trying to be poetic 
by having this change take effect at the winter solstice) so this would 
only be encouraged for legacy systems. I'll leave it to a HI-based 
installer to comment on how easy it is to actually upgrade inverters to 
this wider window. I'd guess you have to order directly from the 
inverter manufacturer to get these settings pre-configured.

When the grid has excess loads and not enough generation, the frequency 
drops. Similarly, excess generation causes the frequency to increase. By 
opening the inverter window on the low end, this keeps all that PV 
generation online when the grid needs as much power as it can summon. 
The inverter window remains a maximum of 60.5Hz since the utility can 
just dial back their own generation-- excess generation is much easier 
to solve than excess load.

In the continental US, grid operators can usually rely on nearby 
resources (natural gas-powered peaker plants, for example) to help 
provide additional power when it's needed in an area. This makes 
frequency problems pretty rare for us. Unfortunately for Hawaii, the 
nearest backup generator is a few thousand miles away. Puerto Rico has 
similar requirements for the same reasons. I believe that next week the 
IEEE 1547 committee will finalize what exactly these windows will be in 
the new edition.

Dave

On 2013/2/4 18:44, Mark Frye wrote:
> Folks,
>
> I was told that because the HI grid has poor frequency control,
> grid-tied inverters have to have their low frequency limit set to 57 Hz
> so they can ride out the worst low frequency events.
>
> I find it hard to believe that this has been done for every single
> inverter installed in HI.
>
> But, what do I know.
>
> Can anyone shed some light on this?
>
> Thanks,
>
> Mark Frye
>
> Berkeley Solar Electric Systems
>
>
>
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