VSC-based Viking HVDC link. Courtesy of Siemens Electric.

The Need for Speed: Voltage-Source Converter Applications for HVDC

June 6, 2024
Expanding the power grid to keep up with the customer’s demand.

Remember that old expression, “May you live in interesting times?” Some say it’s a curse, while others say it’s a blessing. For a techie, it’s a saying that describes what’s taking place in the power delivery system. It covers the excitement those cutting-edge technologies generate as they appear. It describes the anticipation of managing challenges like moving from fossil fuel to clean-energy, and doing it swiftly.

According to the International Energy Agency’s Electricity 2024 report, “Global electricity demand is expected to grow at a faster rate over the next three years, with all the additional demand forecast to be covered by technologies that produce low-emissions electricity.” Those technologies are for the most part wind, solar and energy storage, which continue to increase as fossil fuels are replaced. That brings us to something that is making this a very interesting time: high-voltage direct current (HVDC) technology.

Since we can’t move the load centers closer to all of the anti-global warming generation that’s coming online, we need an efficient transmission system to move it to the load centers. There are several considerations making this challenge even more interesting. Renewable generation like wind farms is moving further from the consumer. In addition, they can be located onshore or offshore and their capacities have increased to the gigawatt (GW) levels. Oh yes, the consumers aren’t pleased with the aesthetics of old-school high-voltage transmission lines.

A New Era

That’s where HVDC technology shines with its voltage source converter (VSC) application. Developers and grid operators have selected VSC-based HVDC as the technology of choice for speeding up bulk power transmission projects. VSC-based HVDC is designed to transmit enormous amounts of power extreme distances via overhead, underground, and submarine technologies, or a combination of them. Plus VSC-based converter stations are compact, requiring a smaller land area than other methods. This now-you-see-it, now-you-don’t approach of switching from overhead conductor to out-of-sight cable systems has proven to be an extremely valuable characteristic in congested urban areas.

An ideal example of this tactic is seen in the Champlain Hudson Power Express project. It uses a combination of both underground cables and submarine cables for its entire length, bringing 1,250 MW into New York City. VSC’s adaptability has proved to be the ideal method for bringing bulk power directly into a densely populated city landscape. These are areas where overhead transmission lines are not be welcomed. VSC-based HVDC’s invisible power line has the aesthetic appeal needed to overcome the “not-in-my-backyard” mind set. That is why it’s being utilized by so many utilities and grid operators worldwide.

Technology of Choice

According to the latest report from Research and Markets, the HVDC transmission market is projected to reach US$ 14.9 billion by 2028 up from US$ 11.4 billion in 2023. This is a CAGR (compound annual growth rate) of 5.4% for the 2023-2028 time frame. They went on to say, “The increasing number of VSC-based HVDC projects, the growing number of renewable energy projects globally, surging demand for reliable power supplies, and supportive government initiatives for power transmission are the major factors driving the market growth globally.”

In other words, VSC-based HVDC is becoming the global technology of choice, which is illustrated by the VSC-based HVDC activity in Europe these days. In the next decade there’s going to be a great deal of wind power capacity added by both onshore and offshore facilities to the European power grid and it needs to be accomplished quickly. The expectations are that somewhere between 80 GWs and 260 GWs are going to be added between 2030 and 2040. That’s a lot of electricity to move to market.

The European Union continues research on developing power hubs and a meshed HVDC grid needed to manage the increasing cross-border power capacities. There is a great deal of actual work taking place with PCI (projects of common interest), which are expected to bridge gaps in the European power system. They are transmission expansion projects like SuedOstLink, SuedLink, Ultranet, and A-Nord to name a few. These VSC-based HVDC links are expected to be the beginnings of multi-terminals leading to that meshed HVDC grid that will eventually be constructed.

Supply Chain Alarms

With all of the VSC-based HVDC projects underway there’s beginning to be a worldwide strain on the supply chain. It’s affecting everything associated with the VSC-based HVDC links from personnel to material. After all, factory space is a finite resource as is the workforce.  As the numbers of these projects grow, what’s the impact it’s having on suppliers? It’s time for “Charging Ahead” to get some inside information from an expert.

If you remember, we talked with Hauke Jürgensen, senior vice president Grid Solutions at Siemens Energy back in the April 2023 edition of T&D World, which resulted in the article “Extending The Power Grid’s Boundaries With HVDC-VSC.” This would be a good time to update that discussion with Jürgensen’s latest insights on how this influx of VSC-HVDC projects are affecting suppliers and what is being done to meet the growing demand. 

Jürgensen began the discussion saying, “The HVDC market has been expanding as never before. Siemens Energy has HVDC projects in every stage of development, from designing, manufacturing and into construction. At the same time, worldwide the number of proposals have been increasing at an unprecedented pace. This situation has been encouraging manufacturers to take a different approach to address this upswing. It’s literally requiring that outside-the-box thinking and it’s encouraging suppliers to consider crossing boundaries that surprise many within the industry.”

Jürgensen explained, “Meeting increased customer demand has suppliers suggesting  customers replace customized specifications with functional specifications. Functional specifications will highlight the need for the standardization of HVDC equipment. The key element for interoperability is standardization, and that is necessary for an industry that has finite resources when it comes to factory space, equipment, skilled personal, etc. A broader supply base to meet the increasing demand for HVDC transmission links. Moving away from proprietary systems to open architecture increases supply chain resources and that speeds up everyone’s HVDC projects, which improves the resilience of the power grid.” 

Jürgensen continued, “Interoperability is also an essential element for developing multi-terminal HVDC technology needed for a meshed HVDC grid. Another crucial element is the HVDC-breaker. Recently Siemens Energy announced they signed a joint development agreement (JDA) with Mitsubishi Electric. We are cooperating with Mitsubishi Electric in the development of an HVDC-breaker. Siemens Energy and Mitsubishi Electric are committed to the development of a HVDC-breaker, which is a crucial element for the future meshed grids. We expect to have the HVDC-breaker tested and operational by 2027 or 2028.”

Jürgensen said, “The JDA HVDC-breaker marks the first time that two HVDC suppliers are working together to commonly develop solutions for multi-terminal and multi-vendor HVDC grids. By working together, Siemens Energy and Mitsubishi Electric are accelerating both the interoperability process and the future development of advanced grids in Europe and worldwide. There is still a lot of work to be accomplished, like the development and installation of meshed grids for example, but Siemens Energy and Mitsubishi Electric are committed to make that happen. It’s a race against time, but the energy transition of the power grid requires it.”

Novel Strategies 

It’s all about expanding the power gird’s capacity and doing it quickly. That’s exactly what European transmission operators are doing. The transmission operators are faced with moving large blocks of offshore wind power from the North Sea inland to load centers to the south and they’re come up with a noteworthy approach. They have defined corridors or “superhighways” as they have been called (see “Superhighways Are Supercharging the Transmission Grid” in the October 2023 T&D World issue for details).

A benefit of this effort has been moving  suppliers toward standardization. As shown with the adoption of ±525 kilovolt (kV) as the standard voltage for these projects. With so many facilities being designed, suppliers are offering common equipment, which is avoiding customization and speeding up deliveries. It’s also cutting costs while giving equipment standardization a boost.

One example of this approach is the Target Grid. It’s the Dutch-German transmission operator, TenneT’s stratagem. Target Grid is basically a gameplan for a future grid able to quickly meet the growing demands for electricity. TenneT has implemented the power corridor concept for moving bulk energy from offshore to customers in the Netherlands and Germany. At last count, TenneT had a framework agreement with their partners for ten ±525 kV, 2.0 GW, VSC-based HVDC facilities and cable systems and there are more in the pipeline.

The steady advancement of VSC-based HVDC applications are taking the technology to its next level. The growing acceptance is building the framework for interoperability and multi-vendor projects, while laying the groundwork for advancing multi-terminal VSC-based networks to meshed grids. It’s happening faster than anyone anticipated. Yes, we’re living in a very interesting time to be part of the power delivery industry! 


About the Author

Gene Wolf

Gene Wolf has been designing and building substations and other high technology facilities for over 32 years. He received his BSEE from Wichita State University. He received his MSEE from New Mexico State University. He is a registered professional engineer in the states of California and New Mexico. He started his career as a substation engineer for Kansas Gas and Electric, retired as the Principal Engineer of Stations for Public Service Company of New Mexico recently, and founded Lone Wolf Engineering, LLC an engineering consulting company.  

Gene is widely recognized as a technical leader in the electric power industry. Gene is a fellow of the IEEE. He is the former Chairman of the IEEE PES T&D Committee. He has held the position of the Chairman of the HVDC & FACTS Subcommittee and membership in many T&D working groups. Gene is also active in renewable energy. He sponsored the formation of the “Integration of Renewable Energy into the Transmission & Distribution Grids” subcommittee and the “Intelligent Grid Transmission and Distribution” subcommittee within the Transmission and Distribution committee.

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