Review sees HVDC taps as key to more flexible clean-energy grids

A new review from King’s College London examines HVDC tap technology, arguing that access points on long-distance power lines could help connect remote communities, industrial users and renewable energy projects without always building new transmission corridors. The paper, published March 31, 2025 in the Chinese Journal of Electrical Engineering, highlights both the promise and the engineering barriers still standing in the way.

Why it matters: - HVDC taps could let grid operators draw power from existing high-voltage direct current lines for local loads, offshore wind, rural electrification and distributed energy resources. - The approach could make future direct current grids more flexible, reliable and scalable without always requiring new transmission corridors or major reconstruction. - The technology may help electricity networks serve both bulk transfers and local access needs as renewable generation, cross-border exchange and distributed power expand.

What happened: - A research team from the Department of Engineering at King’s College London published a review of HVDC tap technology on March 31, 2025. - The article appeared in the Chinese Journal of Electrical Engineering under DOI 10.23919/CJEE.2025.000110. - The review examines HVDC tap technology for renewable-energy integration, rural electrification and hybrid AC/DC power systems.

The details: - The review groups HVDC taps into three categories: series, parallel and hybrid. - Series taps sit directly in the HVDC line, carry full current and take only part of the voltage. - Parallel taps connect across the line, handle full voltage and limited current. - Hybrid taps combine both approaches to improve flexibility and adaptability. - Modular multilevel converters are a major focus because their modular structure, scalability and low harmonic distortion make them strong candidates for HVDC tapping. - The review also covers DC/DC converters, power-flow optimization, HVDC grid substation design and future research directions. - Control strategies discussed include model predictive control, proportional-integral-derivative control, MMC energy control and power synchronous control for voltage source converter HVDC systems. - These controls matter in weak grids, fault ride-through, reactive-power support and coordination among multiple HVDC links, including line-commutated converter HVDC systems. - Earlier HVDC tap projects showed technical feasibility, but protection, voltage stability and cost remained major constraints. - Small taps can still face full line voltage, strict insulation requirements, stability risks and high component costs.

Between the lines: - The review argues that transmission planning is shifting from a simple point-to-point model toward controlled access along the route. - That change would make HVDC links more like shared infrastructure than one-way pipelines. - The authors frame the main challenge as system-level coordination, not just device design. - In practice, taps will need to be smaller, cheaper and more fault-tolerant while staying stable in weak AC grids and fast-changing operating conditions.

What's next: - Further progress depends on compact tap designs, advanced converter technology and coordinated control for hybrid AC/DC grids. - Engineers will need to improve fault management, voltage stability and protection schemes before taps can scale widely. - If those barriers come down, HVDC taps could support multiterminal HVDC networks, connect isolated communities and reduce the need for separate new lines in some settings.

The bottom line: - HVDC taps could become a key building block for cleaner, more resilient and more accessible power systems, but cost, insulation and control challenges still need to be solved first.