Marinus Link: Hitachi Energy’s grid-forming HVDC technology drives Australian renewable energy superhighway - Hitachi Energy

Hitachi Energy is supplying grid-forming HVDC (high-voltage direct current) converters for the Marinus Link, a proposed subsea cable project designed to connect Tasmania's renewable generation to the mainland grid. The technology allows HVDC converters to support grid voltage and stability without a synchronous generator, addressing a known challenge in high-renewables grids where traditional rotating machines that provide inertia are displaced. Hitachi Energy framed the deployment as critical infrastructure for Australia's renewable transition.

Where this fits

Marinus Link illustrates a hidden cost of the renewables-only path: grid stability no longer comes free from thermal generators. Synchronous condensers, HVDC grid-formers, and fast-acting power electronics now become compulsory capital spend. This is not a flaw in the technology; it is real engineering. But it is a cost that renewable-per-megawatt headlines do not capture. The firming and grid-support layer, HVDC infrastructure, batteries, fast-frequency response devices, and interconnection overbuild, is the difference between cheap megawatts and a reliable grid. Firm, dispatchable sources like nuclear produce inertia and voltage support as a byproduct of generation; weather-dependent sources require it to be bolted on separately.

What it means

Australia is now committed to building not one energy system but two: renewable generation and a parallel grid-support apparatus to make it stable. Each link, synchronous condenser, and battery adds to the whole-system bill. Marinus Link itself remains in planning and faces cost and timeline uncertainty. The pattern is clear: a renewables-only grid works only if you accept high capital cost and China-sourced component dependence for every layer of the system, generation, firming, and now stability itself.