[RE-wrenches] AC Coupling Standard?

Eric Smiley eric at vecoop.ca
Fri Dec 2 08:25:45 PST 2022

Utilities have used and continue to use this method of control for their
own generators, except they refer to it as Droop Control. In addition to
Frequency/Watt response Voltage/VAR response is also used.

Building inverters that mimic the behaviour of spinning generators is a
great development as some jurisdictions now require, for example,
ride-through capability when brown-outs occur, rather than the older
requirement for inverters to simply turn off when voltage or frequency
dropped below certain limits, which just exacerbated brown-outs.
Essentially an inverter can be programmed to have "inertia" just like a big
spinning generator.
Larger grid-interactive inverters have done this for a while, with very
complex settings, but we are now seeing smaller residential and
commercial inverters with similar capabilities.
This industry keeps evolving and improving, which is great for keeping us
on our toes and I find it very exciting.

*Eric Smiley,* Project Manager
eric at vecoop.ca
T: 250.703.6004 <+12507036004>
T: 888.386.0116 <+18883860116>
*VIRIDIANENERGY.CA <https://viridianenergy.ca/>*

* <https://viridianenergy.ca/>*

On Fri, 2 Dec 2022 at 07:08, Windy Dankoff via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Dear Mike,
> As co-author of upcoming book "The Handbook of Solar Water Pumping", we
> have expanded its definition to include micro and national grid-tied
> systems in which pumping is synchronized with power availability from PV. I
> had known about frequency-based load control for microgrids (from an
> SMA-based microgrid I toured in Israel). I had no idea it was a happening
> system on public grids until I read your response here. I love how it
> requires no communication lines or digital signals. It's a "natural" and
> logical concept from the old days of spinning generators under varying load.
> I see your PG&E reference, but is there also a reference text you can
> recommend that I can use in the book as a universal explanation of how this
> works?  It can be SMA documentation, or other ref.  You can reply here if
> it's useful to the list, and/or contact me off-line.
> Thanks!  – Windy
> On Dec 1, 2022, at 5:47 PM, re-wrenches-request at lists.re-wrenches.org
> wrote:
> *From: *Harry Mahon <Michael.Mahon at sma-america.com>
> *Subject: **Re: [RE-wrenches] AC Coupling Standard?*
> *Date: *December 1, 2022 at 5:47:18 PM MST
> *To: *RE-wrenches <re-wrenches at lists.re-wrenches.org>
> Definitely it is possible for newer grid-interactive inverters.  However,
> for grid-tied operation, the utility that runs the grid sets the rules (and
> sets the setpoints as it were), and it can be confusing....
> Looking at PG&E’s Rule 21 tarriff (submitted Aug 12, 2022, effective Nov
> 4, 2022) Freq-Watt reuirements are:
> “When system frequency exceeds 60.036 Hz, the active power output produced
> by the Smart Inverter shall be reduced by 50% of real power nameplate
> rating per hertz (5% of real power nameplate rating reduction per 0.1
> hertz)”
> Bottom of Sheet 207 of :
> https://www.pge.com/tariffs/assets/pdf/tariffbook/ELEC_RULES_21.pdf
> So a 5kW inverter needs to ramp at 2.5kW/Hz.  But if it is only producing
> 2.5kW, it has to be at 0W at 61.036Hz.....
> Mike
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