Brochure · EN — 14-page Siemens Energy brochure (A4 portrait, © Siemens Energy 2022, Article No. PTSO-T10004-00-76DE) presenting HVDC PLUS®, the voltage-sourced converter (VSC) HVDC transmission technology based on trendsetting modular multilevel converters (MMC). It frames the grid challenges (intermittent renewables, decreasing conventional generation, grid access for offshore wind and remote loads), describes the technology benefits (controlled power supply in either direction, 'firewall' against disturbances, low switching frequencies, nearly ideal sinusoidal AC waveforms typically eliminating harmonic filters, gas-insulated DC compact switchgear up to ±500 kV cutting DC-switchyard space by up to 90 percent), the application families (long-distance transmission, interconnectors, grid access, multi-terminal), the half-bridge and full-bridge MMC topologies (new half-bridge power module with DC current capability of more than 2 kA in a 6.5 kV voltage class), and lifecycle/after-sales services. Honest-thin note: the brochure is market-facing and contains no product ratings table — the only quantitative figures printed are the headline values reproduced verbatim here.
An ever-increasing demand for energy, a steadily growing share of intermittent renewable resources and a decrease in conventional power generation are the challenges facing today's power markets (p. 2). Grid operators face ever-increasing requirements for grid stability, power quality, and reliability; they need efficient, innovative solutions to keep the transmission system stable and reliable, and to maintain the safety and security of the supply at all times (p. 3).
Managed grid complexity: with a multitude of intermittent power generators replacing a small number of highly predictable conventional power sources, grid operation has become very complex — dealing with thousands of individual players while stabilizing the AC grid, and providing transmission capacity wherever and whenever it is needed. Improved grid access is a further challenge, either for remote renewable power generators such as offshore wind farms or for remote load centers like oil rigs. And customers need competitive solutions over the entire lifecycle: an optimal balance between functionality and performance on one hand and investment as well as operational costs on the other (lowest CAPEX and OPEX) (p. 3).
Flexibility and power quality call for efficient use of HVDC PLUS® technology with project-specific adaptions based on the Siemens Energy HVDC PLUS Reference Designs, and an HVDC PLUS® point-to-point transmission system which can optionally expand into a multi-terminal system with three or more converter stations. A solution that improves existing grid infrastructure must address: maximum availability; stabilization of the AC network; future-oriented, flexible solutions responding to varying power market requirements; ability to provide grid access for renewable energy sources; power exchange between interconnected systems and between asynchronous grids; economic, adaptable, and compact solutions; and a maintenance-friendly, safe, and reliable design with comprehensive lifetime services (p. 3).
As an innovation leader, Siemens Energy has developed an advanced, universally applicable solution for power transmission with its voltage-sourced converter (VSC) technology HVDC PLUS®. The innovative solution offers a controlled power supply in either direction and is ideal as a 'firewall' against disturbances developing in highly loaded AC grids. HVDC PLUS® technology is based on the trendsetting modular multilevel converters (MMC) and offers numerous technical and economical benefits (p. 4).
Economical and environmental benefits: HVDC PLUS® gives top priority to both energy and resource efficiency. The MMCs operate with low switching frequencies, which reduces losses. Due to generation of nearly ideal sinusoidal waveforms on the AC side, typically the need for harmonic filtering is eliminated — resulting also in less time and costs for planning, engineering, construction, and commissioning. The compact design means lower space requirements and thus reduced property costs (p. 4).
The compact footprint can be further reduced, e.g. using gas-insulated DC compact switchgear, available up to ±500 kV. Compared with air insulation, the gas-insulated solution reduces space requirements for the DC switchyard by up to 90 percent (p. 5).
Stabilization of the AC network: HVDC PLUS® is completely appropriate for steady-state and dynamic AC voltage control, independently on each station. Its typical advantages are apparent when weak AC networks are being connected: low dependency on short-circuit power, voltage, and frequency of the AC networks; reactive power can be generated or consumed independent of active power transmission; and during AC transmission network restoration (for example, after a blackout) HVDC PLUS® can provide system recovery ancillary service (SRAS) (p. 5).
Operational advantages (sidebar, p. 5): a very high level of system reliability, and redundancy for all key components of the converter control; standard control and protection system with hardware and software in hot standby; minimized maintenance and service requirements; compact station design with typically no harmonic filters; and black-start capability to improve speed of recovery of interconnected grids.
Health and safety: the stated goal for all HVDC PLUS® transmission projects is to apply the highest possible safety standard in order to reduce the number of incidents to zero. Systems are designed using a risk-based engineering approach to assure a risk-free and safe design, a 'safety-first' construction process, and safe operation. The brochure cites two project teams recognized by the British Safety Council — one awarded the 'Sword of Honor' and one achieving five stars in the Five Star Occupational Health and Safety Audit (project names omitted here per catalog guardrail) (p. 5).
HVDC PLUS® is a technological breakthrough for highly efficient power transmission. Available applications include long-distance transmission via overhead lines and cables as well as network interconnectors and grid access solutions; the application panorama is annotated 'several 100 km' (p. 6).
Long-distance transmission: for covering long distances, HVDC PLUS® power transmission is often the most efficient and economic solution. A variety of media can be used for power transmission: cables, or even existing overhead lines. The page shows single-line schematics for both configurations: Long-distance (System A — AC — DC Line — AC — System B) and Back-to-back (System A — AC — DC Circuit — AC — System B) (p. 6).
Interconnectors: HVDC PLUS® interconnectors connect independent national and/or regional grids regardless of their frequency. By converting the AC power into DC and from DC back to AC, the converters facilitate stabilization and improvement of grid operation; grid code requirements are met. One example is a back-to-back interconnector where both converters are at the same location (p. 6).
Grid access: HVDC PLUS® is the ideal space-saving solution to provide grid access to remote offshore wind farms with its dynamic fast control, making regenerative energy sources fit for the grid and connecting them according to the conditions of each particular grid code by providing the required voltage quality at the grid coupling point. The DC Compact Switchgear offers additional space savings on the platform. HVDC PLUS® also provides power for connecting remote loads: from shore to offshore oil and gas platforms, and for mines (p. 7).
Multi-terminal connections and future DC grids: in addition to the most commonly applied point-to-point connections, HVDC PLUS® facilitates expansion to multi-terminal systems and further development to DC grids in the future to back up existing AC grids. Due to its operation principle — keeping the DC voltage constant in one polarity and changing the direction of power transfer by reversing the current — HVDC PLUS® is ideally suitable for multi-terminal applications. This enables stagewise development of transmission solutions and high flexibility to expand existing schemes in case of future changes in power grids or load flow scenarios (p. 7).
A converter-station rendering (p. 7) labels the seven main station elements: 1 — converter transformers; 2 — cooling; 3 — AC switchyard; 4 — control and protection; 5 — DC compact switchgear; 6 — DC yard; 7 — converter hall.
Half-bridge type MMC: the power capacitor can be connected in one polarity to the terminals. The highly efficient HVDC PLUS® half-bridge topology is used for most HVDC PLUS® applications today. It has proven its excellent reliability in practice and is particularly suited for offshore applications (p. 8).
This technology also features the latest innovation, the new half-bridge module based on cutting-edge IGBT technology with a DC current capability of more than 2 kA, which fits to the new development in XLPE cable technology. Its high power density results from its 6.5 kV voltage class and leads to reduced converter hall sizes. By a smaller number of submodule levels, losses are lowered even more. The module photo is captioned 'The next generation of power modules for more than 2 kA' (p. 8).
For HVDC PLUS® overhead line configurations, MMC in full-bridge topology is the right choice, as this allows for selective clearing of DC line faults. Full-bridge type MMC: the power capacitor can be connected in either polarity to the terminals. This means that the DC voltage is independent of the AC voltage and can be controlled to zero or even be entirely reversed to maintain current control on the AC and DC sides and also under short-circuit conditions; the DC voltage can also be controlled over a wide range, including both polarities (p. 9).
Siemens Energy HVDC PLUS® technology is based on strategies proven in a wide range of industrial applications of VSC technology, and offers the following advantages (verbatim bullet list, p. 9): immediate initiation of DC fault clearing by reversing the DC line voltage polarity for a short period of time in order to extinguish and de-ionize the electric arc, followed by the possibility of multiple restart attempts; flexibly controllable DC voltage provides a voltage ramp-up characteristic which takes into consideration project-specific AC conditions; flexible operation at a reduced voltage as a precautionary measure in adverse weather conditions and increased air pollution; and minimized fault clearance time for multi-terminal systems, when combined with selective fault detection.
Siemens Energy positions itself as the inventor of HVDC PLUS® and the most experienced partner on the market today. Track-record firsts as printed: the first to offer HVDC PLUS® in MMC technology, the first supplier of 2 x 1,000 MW with VSC technology, and the first to upgrade an existing HVDC PLUS® with black-start capability. As turnkey supplier the company can assume responsibility for the entire lifecycle of a project, from the first analysis through creation of an optimized solution to commissioning — including after-sales services from operation to the reliable supply of spares (p. 10).
The lifecycle wheel (p. 11) spans: technical clarifications; overall project management; engineering and design; site facilities and civil works; production; procurement; factory testing; transport; on-site installation and commissioning; training; after-sales services; and financing support and consulting.
HVDC PLUS® after-sales services (p. 11) — to increase transparency of assets: on-site condition assessments ('health checks'), condition monitoring and diagnostics, remote services, asset management and advisory services. To ensure high asset availability: preventive maintenance, field service and repair, spare parts, 24/7 expert hotline and technical support, obsolescence management. To optimize asset performance: refurbishment, upgrade and uprate. To support operation management: asset operation, spare parts management, customer qualification and training, cyber security services. Services range from standard preventive maintenance to cyber security and asset management consulting; retrofit and refurbishment services assist in extending the lifetime of HVDC PLUS® assets (pp. 10–11).
Honest-thin note: this brochure is a market-facing overview and contains no product ratings table — no MW/kV rating matrix, losses, dimensions, or standards-compliance data are published for the HVDC PLUS® platform itself. The only quantitative figures printed in the technology pages are collected verbatim in the table below; no other values have been added.
The brochure closes with three reference-project case studies (pp. 12–13) giving per-project plant type, power rating, and voltage levels; these pages name customers and are omitted from this entry per the catalog's customer-privacy guardrail. Publication data (p. 14): published by Siemens Energy Global GmbH & Co. KG, Transmission, Freyeslebenstraße 1, 91058 Erlangen, Germany (for the U.S.: Siemens Energy, Inc., Transmission, 4601 Six Forks Road, Raleigh, NC 27609, USA); siemens-energy.com/hvdc; Article No. PTSO-T10004-00-76DE; © Siemens Energy, 2022; 'Siemens Energy is a trademark licensed by Siemens AG'; subject to changes and errors.
| Figure (as printed) | Value | Page |
|---|---|---|
| Gas-insulated DC compact switchgear, available up to | +/- 500 kV (as printed) | p. 5 |
| DC-switchyard space reduction vs. air insulation, up to | 90 percent | p. 5 |
| Long-distance application panorama annotation | several 100 km | p. 6 |
| New half-bridge module — DC current capability | more than 2 kA | p. 8 |
| New half-bridge module — IGBT voltage class | 6.5 kV | p. 8 |
| First supplier of (with VSC technology) | 2 x 1,000 MW | p. 10 |
| Multi-terminal system option | three or more converter stations | p. 3 |
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