Re: Grand Apagon - Electricity (not) in Spain

On 2025-05-01 02:36, Chris Jones wrote:

On 30/04/2025 1:07 am, Martin Brown wrote:

The idea that renewable sources make the grid frequency harder to manage sounds like total nonsense.

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It is pretty much accurate. The local feed in for domestic PV track whatever frequency they see on the network. The big problem is that without the large spinning generators and the energy stored in that angular momentum the frequency is able to shift rather too quickly.

 The problems are largely self-inflicted (or self-fulfilling prophecies) created by those who fear allowing renewables on the grid. In Australia they were so fearful of solar power being fed into the grid under unusual circumstances like islanding, thay they set a very tight limit requiring the solar inverters to shut down if the frequency dips slightly below nominal. So, once lots of PV was installed, when a coal- fired generator fails and the frequency dips, some "dangerous" PV power shuts down too, causing the problem to get worse, "just to be safe". It isn't an inherent weakness of the technology, it is a direct consequance of regulations written by those who fear or oppose renewables. Fortunately this particular problem was recognised and new inverters are now no longer required to shut down when the frequency dips within the foreseeable range.
 If the specifications for the inverters are written based on sound engineering and simulation of the grid behaviour rather than fear and ideology, it would be quite feasible to alter the algorithm in the PV inverters to help stabilise the grid frequency. For example, you could make it simulate what a spinning generator would do, or very likely something much better.

Exactly.

 There is nothing magic about the current from a rotating generator that cannot be exactly replicated by an inverter that synthesises the same waveform and produces it with power semiconductors instead of a steam engine. Especially domestic single-phase inverters already incorporate enough capacitance to buffer the PV energy supplied to them, so as to supply a sinusoidal current to the grid, and this storage allows it to shift the phase of the current relative to the voltage however required in order to help stabilise the system, if only it were allowed to and required to by regulations.

That's what I said on another part of the thread, but with less detail because I know less :-)
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Cheers, Carlos.