The immediate impetus for the resolution appears to have been the recent blackout in Spain and Portugal, which has been generally attributed to the lack of synchronous generation on the power grids of those countries.....
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Denmark has links to Sweden and Norway and of course with Germany since they share a ground border with them. I was curious to see how things shaped up with ‘import and export of electrical energy’ and this data is from 2023….
The numbers are the imported and exported electrical energy in TWh....
Country Imports Exports
Sweden 8.54 1.47
Norway 5.60 (very small/negligible)
Germany 2.45 9.26
Totals 16.89 10.73
Bottom line is that this may have something to do with the recent blackout in Spain/Portugal but up to now, the adjacent countries are what has sufficed for synchronous generation and inertia for Denmark… the advantage of being a small country that is next door to a big country where the neighbors can’t act as a big battery. The problem is that these other countries too have jumped on the UI (unreliable/interruptible) bandwagon. Norway is still fine since almost all of its electrical power is generated by hydro but Sweden is up to nearly 25% wind and Germany is at 60% and therefore are the same type of risk as what took down Spain/Portugal.
HVDC links can and do function as virtual inertia. The newer links are VSC based those can be driven to not follow the grid like a PLL converter station they can push both active power, reactive power and virtual inertia. Google scholar has a number of paper’s confirming this and how it’s implemented in places that have large HVDC links especially under sea cables since you cannot send HVAC under the ocean the mag fields and seawater do not play nice.
Any VSC power converter can be driven to produce active,reactive and frequency/phase control it’s all in the driver electronics. It’s much cheaper to just phase lock loop an power converter to the grid and let it grid follow. It’s not a technical issue its a mandate that all new power electronics must be VSC based, with active,reactive and frequency control this would solve the inertia issue as well given that VSC can team up to produce gigawatts worth of inertia ancillary services.
… the advantage of being a small country that is next door to a big country where the neighbors can’t act as a big battery.
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That line should have read “... where the neighbors CAN act as a big battery.”