Hmmmm, I don't see why. The automatic control systems and human operators who manage the grid control frequency within tight limits, but they are often playing 'catch up' in one direction or another. Frequency will often run low for extended periods of time during daytime peak low periods, and then will intentionally be run high overnight to compensate.
Also, from the system operators point of view, residential PV output is not generation, which they control to manage frequency and voltage. It's negative load that fluctuates like all other load, and what the operators see and have to contend with is the total load on the system net of any residential PV.
Certainly you wouldn't want residential PV generation to cut back just because system frequency went above 60 Hz.
garygid said:
I suspect that PV Inverters (DC to Grid AC) should automatically scale back production of AV if the Grid Voltage rises "too" high, right?
Wind generation is already being throttled at times in some places, because it is the last resort in localized situations where it is the wind output that is overloading the lines and there simply are no fossil units that could be curtailed to relieve the overloads. Transmission systems are designed to meet (in most places) summer peak loads, when maximum generation is required, with lesser attention paid to winter peak loads and summer 'shoulder' peaks. They are not designed with consideration given to minimum load periods, which is when wind generation tends to generating the best.
Also, the best places for wind generation tend to be places where there is not much existing generation, transmission, or load. So again, in certain places and at certain times, even though there may not be much wind capacity in comparison to total system capacity, there is more wind generation than can be used and no non-wind generation to back down. It's not a big problem yet, but it is happening and will only happen more often in more places as wind capacity becomes a larger piece of the generation mix.
In the upper midwest, the need to back down wind generation is already happening enough that the regional transmission operator is preparing proposals to submit to the Fededral Energy Regulatory Commission to make wind generation automatically dispatchable, under the control of the system operators, so that wind farms can be easily backed down when system conditions call for it.
drees said:
While it's possible to design an inverter to regulate the amount of AC power it produces from PV panels, the only situation that I've seen this done is in off-grid setups to avoid overcharging batteries.
I believe that some SMA inverters will look at the AC frequency and adjust output based on that.
http://www.sma.de/en/products/knowledge-base/sma-inverters-as-grid-managers.html
For example, some can be configured to reduce output if the grid frequency rises above 60Hz - this typically indicates an oversupply of power on the grid.
Of course, this isn't optimal - in general wind/solar generation is throttled only as a last resort as it has the lowest running cost - everything else typically will cost more so it's more cost effective to throttle down any fuel burning plants first.
It will take some time for enough renewable generation to show up on the grid to incur frequent throttling - when that happens expect demand for storage devices to take off. At that point it won't take long for smart-grid EVs to show up - in aggregate there will be a ton of battery capacity available if they are plugged in.
