AFAIU, the main technological advances are in materials science in the conductor, which is decades back, and in the solid state power electronics for the voltage conversion, since the 1970's.

The big limit on HVDC is that its for point to point transmission ... AFAIU, multi-terminal is a headache with DC, requiring active management. So HVAC would continue to be used the distribution grid because one line for each local substation would be a dramatic increase in capital costs, as would a HVDC to AC inverter at each local substation.

But HVDC requires fewer conductors, has lower losses over long distances (it has higher transmission losses are at the origin and terminal, but lower over the line), and does not require synchronization between origin and terminal.

So for the application of long-haul point-to-point transmission, its the choice, for distances of 800km+ ... the Inga Dam to Shaba copper mine in the Democratic Republic of Congo is a line of 1700km.


I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.