Caithness Moray HVDC link, Blackhillock. Courtesy of Hitachi Energy
Caithness Moray HVDC link, Blackhillock. Courtesy of Hitachi Energy

Superhighways Are Supercharging The Transmission Grid

Sept. 27, 2023
Technological advancements can make the electricity supply more resilient.
When the global warming experts gather to discuss the technologies needed to combat the extreme weather events fueled by climate change do they talk about powering those technologies? The short answer is no. It’s one of those topics that’s usually underrepresented. That’s because it’s another case of us doing such a great job of supplying electricity no one givesmuch thought about it. But these technologies require power to do their tasks.

If we are going to electrify the transportation system, the electric vehicles doing it require charging, and this is a new load on the grid. Reaching a carbon neutral industrial sector involves cutting sources of greenhouse gas emissions, which increases the industrial sector’s demand for more electricity. These are only two examples and there are many more, and they all represent adding more load to the power grid. 

Critical to all the additional loads from these technologies is increasing the grid scale wind and solar energy capacities needed to replace the decommissioned fossil-fuel generation. Deploying the technologies and the renewables requires a great deal of support from all the stakeholders including regulators and governments. Luckly this support has been improving.

Much Needed Support   

July ended with a bang in the area of regulatory support! FERC (Federal Energy Regulatory Commission) issued its final rule for easing the nationwide backlog of renewable energy projects stuck in interconnection queues. Without going to deeply, it’s a major step for streamlining the interconnection process. Foremost, it’s implementing a first-ready, first-served cluster study procedure. Next, interconnection studies will be performed collectively, rather than separate studies for each. There are other incentives like deadlines and penalties, but you get the picture.

Technologically, there’s a lot to choose from when it comes climate proofing the grid and making it more resilient. “Charging Ahead” has delivered several articles this year about HVDC’s (high-voltage direct current) exceptional capabilities in this area. The year started off with the Champlain Hudson Power Express, which addressed the public’s resistance to adding overhead transmission circuits. It’s a stealth approach moving 1,250 megawatts (MW) via submarine and subterranean cabling from Canada to New York City.

Another article focused on a project developed to address some unique problems that were being encountered as massive offshore windfarms move further from the shoreline. The BalWin1 and BalWin2 offshore grid connections take advantage of voltage source converter (VSC) technology. VSC-HVDC can be operated in bipolar mode giving the BalWin1 and BalWin2 HVDC links the ability to move gigawatts (GW) of power over much further distances. Each of its links move 2,000 MWs from offshore directly to inland load centers located within Germany.

The last article looked at the SunZia transmission project, which applies another of VSC-HVDC technology’s abilities of combing with power electronic controllers. In SunZia’s case, the HVDC transmission line technology was coupled with AC chopper technology. This combination tames any voltage imbalances caused by any line faults that may develop in the course of operation. This results in a robust system that allows the SunZia project to reliably bring 3,000 MW of wind generated power from New Mexico to Arizona for use in southern California.

Supercharging Superhighways 

Each of these projects exhibited a steady progression of adapting cutting-edge technology to a changing power grid. It’s critical for the power delivery system’s ability to supply our customers’ growing demands for more clean electricity and VSC-HVDC technology is a powerful tool in that task. The projects mentioned above show how an established technology can be combined with changing realities. This integration gives grid operators an edge when it comes to blending sustainable clean energy into an established power grid with multiple energy sources.

A few months ago, the United Kingdom (UK) gave the world an indication of governmental commitment to clean energy. The UK announced it intends to increase its offshore wind capacity from about 13.7GW to 50 GW by 2030. In order to achieve this goal there will have to be some innovative measures to supercharge the permitting, planning, infrastructure upgrades, etc. processes. One such unique approach is the development of “multiple onshore VSC-HVDC links to accelerate the integration of bulk renewables onto the UK power grid.

As part of this effort, Scottish and Southern Energy Network (SSEN) Transmission announced the selection of Hitachi Energy as their preferred technology provider to supply multiple HVDC converter stations to accelerate the integration of bulk renewables into the UK power grid. SSEN reported that “The parties signed a framework agreement that includes the deployment of up to five HVDC power corridors, or electricity transmission superhighways, to enable large amounts of future renewable power to be transported from northern Scotland to areas of higher consumption in the south.”

It's Complicated    

Given the complexity of the framework agreement, which is currently being finalized, it seemed like a good subject to discuss with Niklas Persson, Managing Director, Hitachi Energy’s Grid Integration business. We started off looking at the physical makeup of the system being developed. The first two projects under the framework agreement are the Arnish-Beautly and Spittal-Peterhead links. Each of these HVDC links will transmit up to 2.0 GWs at ±525 kilovolts (kV). These projects are expected to begin in 2024 and be operational in 2030.

The Arnish-Beautly link runs from the Western Isles to Beautly substation on the Scottish mainland with planned upgrades of powerlines from Beauly to Peterhead in Aberdeenshire. The Spittal-Peterhead link consists of a 136.7 mile (220 km) subsea cable route with new HVDC converter stations located close to Spittal substation and Peterhead substation. This is a good point to talk about another aspect of the HVDC power corridors. It’s the continuation of moving large blocks of power to the consumer.

The joint venture between SSEN Transmission and National Grid Transmission is set to interconnect the Scottish and English power grids, so let’s see how it fits with what is being discussed here. The Eastern Green Link 2 (EGL2) project begins at Peterhead. EGL2 is a 2.0 GW ±525 kV 237.6 mile (440 km) subsea cable and 43.5 mile (70 km) underground cable linking Peterhead in Scotland to Drax, North Yorkshire, England. The project is expected to be operational in 2030.

Persson points out, “This collaborative effort can only be achieved with advanced technologies and new ways of working. By structuring the collaboration as a framework agreement, it enables Hitachi Energy to invest in new production capacity and to undertake large-scale recruitment drives. It also strengthens collaboration, standardization of solutions, and synergies between projects.”

Persson continued, “The integration of renewables requires solutions that make the grid resilient, stable, and flexible. Hitachi Energy’s innovation and long development of VSC-HVDC technologies, power electronics, and MACH control and protection technologies are designed to meet the requirements alongside many other landmark grid integration projects. This framework agreement reinforces how Hitachi Energy’s HVDC technology can be utilized effectively.”

Persson explained, “This approach also shows how new business models enable the scale needed to speed up the energy transition. This new methodology allows Hitachi Energy to plan in advance to increase manufacturing capacity, expand and train the workforce, and maximize standardization to increase synergies between successive projects. It also prepares the way for future developments of sharing renewable resources between the UK and European Union (EU).”

VSC-HVDC Backbone

In addition to multiple transmission superhighways, there is a lot of interest in multi-terminal hubs and artificial energy islands forming a VSC-HVDC backbone grid. Such a VSC-HVDC transmission infrastructure would provide backbone flexibility required by tomorrow’s load flow patterns. With Europe announcing plans to add about 450 GWs of offshore wind generation by 2050, the push for HVDC interoperability is moving up the scale when it comes to criticality. The challenge of interoperability is getting a system, subsystem, and all of their components to work together.

Along with the technical issues there are many non-technical topics that have to be addressed as the industry moves towards implementing multiple vendor multi-terminal systems. Technically standardization is a massive challenge followed by system modeling and planning. On the non-technical side, contractual issues, warranties, intellectual property rights, a mass of regulatory matters, and a slew of legal uncertainties to name a few have to be addressed.

In the EU, there are HVDC interconnections between countries, between offshore generation and onshore power grids, and between regions within HVDC power corridors. They are looking forward to the time when there will be HVDC mesh-grids comprised of multi-national grid connections, artificial energy islands, and more sophisticated power electronics. Granted it’s theory now, but the next-gen VSC-HVDC (i.e., a backbone HVDC grid) is in the foreseeable future.

The EU’s InterOPERA project was formed earlier this year with the “goal of enabling interoperability of multi-vendor HVDC grids.” They seek to improve grid forming capabilities of both offshore and onshore converters. As gigawatts replace megawatts in the battle against global climate change, this ambitious enterprise is needed. It’s an undertaking that must be won!

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