Presentation · EN — 29-slide Siemens Energy Grid Technologies standard presentation 'HVDC PLUS© — One Step Ahead' (status February 2025, classification Unrestricted) covering the basics of voltage-sourced converter (VSC) HVDC. It contrasts HVDC PLUS© (VSC, IGBT, up to 2,500 MW, cables up to 525 kV DC, OHL up to 525 kV / 800 kV) with HVDC Classic (LCC, light-triggered thyristors, up to 10,000 MW, OHL up to 1,100 kV); traces the evolution from two-level and three-level VSC to the modular multilevel converter (MMC); walks through the P-Q operating capability and the MMC feature/benefit set; explains the symmetrical-monopole and bipole topologies and the converter-station layout; details each key component (interface transformers, star point reactor, insertion resistor, MMC power modules and towers, converter reactors, PLUSCONTROL control and protection, deionized-water cooling); and compares half-bridge and full-bridge power modules, with full bridge adding DC fault-current clearing for overhead-line transmission. Honest-thin note: as a technology-basics deck it publishes platform headline ratings and converter-design figures only — no project-specific ratings table; the deck's history timeline and reference-project map name third-party projects and are omitted from this entry per the catalog guardrail.
The deck opens the technology chapter by answering 'Why high voltage direct current (HVDC)?' with a side-by-side of the two converter families: LCC — HVDC Classic and VSC — HVDC PLUS© (slide 3).
HVDC PLUS© is the voltage-sourced converter (self-commutated): its semiconductor switches have turn-on and turn-off capability, implemented with insulated-gate bipolar transistors (IGBT). HVDC Classic is the line-commutated converter (current-sourced), built on thyristors with turn-on capability — direct light-triggered thyristors (LTT). The headline ratings as printed on the slide are collected in the table below (slide 3).
| Parameter (as printed) | VSC — HVDC PLUS© | LCC — HVDC Classic |
|---|---|---|
| Converter principle | Voltage sourced converter (self-commutated) | Line commutated converter (current-sourced) |
| Semiconductor | Insulated-gate bipolar transistor (IGBT), turn-on/-off capability | Direct light-triggered thyristor (LTT), turn-on capability |
| Power rating | Up to 2,500 MW | Up to 10,000 MW |
| With cables | Up to 525 kV DC | Up to 600 kV |
| Overhead line (OHL) | Up to 525 kV (800 kV) | Up to 1,100 kV |
A history timeline (slide 4) positions Siemens Energy as a leader in VSC technology from the first static var compensators of 1974/75 (built by GE and Westinghouse, businesses now part of Siemens, per the slide footnote) through SVC PLUS© and HVDC PLUS© milestones. The milestone claims as printed: the first MMC STATCOM (2009, UK), the world's first MMC VSC HVDC (2010, USA), the first offshore MMC HVDC (2015, Germany), the largest VSC HVDC at 2 x 1000 MW (2017, Spain/France interconnection), a ±400 kV symmetrical-monopole link (2019, UK/Belgium), a link expandable to multi-terminal (2019, Denmark/Netherlands), and the first full-bridge HVDC on a hybrid overhead line (2023/2024, Germany) with the highest VSC converter voltage. The individual project names attached to these milestones on the slide are omitted from this entry per the catalog guardrail.
The evolution of VSC HVDC technology is illustrated as a topology progression — two-level, three-level, multilevel — each shown with its AC output-voltage waveform over time; the multilevel waveform approaches the ideal sinusoid (slide 5).
The Modular Multilevel Converter (MMC) is presented with the half-bridge arm arrangement between +Udc/2 and −Udc/2: a modular arrangement of identical two-terminal power modules stacked per arm. The printed advantages are a low level of harmonics and HF noise, low switching losses, and the modular arrangement itself (slide 6).
In the half-bridge MMC, the AC and DC voltages are controlled by the converter module voltages; the DC voltage is always higher than the AC voltage (slide 7).
The MMC feature set is summarized as: grid access of weak AC networks; independent control of active and reactive power; supply of passive networks and black-start capability; high dynamic performance; and low space requirements. A P-Q operating diagram spans −1.25 to +1.25 p.u. active power (rectifier/inverter) and −1.00 to +1.00 p.u. reactive power, annotated with the design specification, voltage limit, and current limit (slide 8).
A follow-up features/benefits slide lists the features as printed: high modularity in hardware and software; low generation of harmonics; low switching frequency of semiconductors; use of well-proven standard components; sinus-shaped AC voltage waveforms; easy scalability; reduced number of primary components; and low rate of rise of currents even during faults (slide 9).
The benefits as printed: high flexibility, economical from low to high power ratings; only small or even no filters required; low converter losses; high availability of state-of-the-art components; use of standard AC transformers; low engineering efforts; high reliability, low maintenance requirements; and a robust system (slide 9).
Two major system topologies are shown as single-line schemes between Terminal A and Terminal B over OHL and/or cable (slide 10): the symmetrical monopole, which has no grounding on the DC side, and the bipole, with return-path options — metallic return or ground/sea return — and a 'rigid bipole' variant if no return path is available. A hybrid tower arrangement is also depicted.
The station-design slide identifies the main areas of an HVDC PLUS© converter station on an aerial rendering: transformer, AC switchyard, converter AC yard with star point reactors, insertion resistors and bypass switches, converter reactors, converter (hall), and DC switchyard (slide 11).
A key-components single-line overview places these elements between AC System A and AC System B: transformers, star point reactor, insertion resistor with bypass switch, the modular multilevel converter, converter reactor, current measuring devices, the control, protection and monitoring system, DC switchyard, and the DC cable / transmission line (slide 12).
Three photo slides present the AC-side key components: interface transformers, which adjust the AC voltage to the converter (slide 13, site photos of Siemens-branded converter transformers between fire walls); the star point reactor (slide 14, switchyard photo); and the insertion resistor, highlighted in the AC-yard structure (slide 15).
MMC — modular design: the power module is 'the power electronics'; the submodule arrangement pairs it with the DC capacitor into a two-terminal building block (slide 16).
MMC — converter design: the '6-Pack' is the shipping unit ex-works and allows replacement of single power modules. Converter towers are built as a double tower with 3 floors (72 submodules) or 4 floors (96 submodules), giving defined internal voltage stress and a compact installation (slide 17). A summary slide shows the build-up from IGBT device to power module to submodule string to complete converter tower, with the printed attributes: compact design, modular design, lower space requirements, advanced VSC technology, maintenance friendly (slide 18). An example converter-hall interior photo follows (slide 19).
Converter reactors: each phase unit forms a parallel connection of three voltage sources; the reactors damp balancing currents between the different phases and limit the current gradient during severe faults (slide 20).
Control and protection: the PLUSCONTROL architecture is drawn across three levels — operator level (local HMI, remote HMI, SCADA interface via WinCC OA / Zenon, RCI), C&P level (CCS with MMS 1…n), and I/O level (measuring of voltages and currents, control-level devices) — commanding the converter power modules, switchgear and auxiliaries (slide 21).
Auxiliary system — cooling concept: parallel cooling of all power modules gives identical operating conditions for all power modules (aging of the IGBTs), a long-term proven concept from HVDC Classic, with stricter requirements for IGBTs compared to thyristors (heat capacitance of chips, wire bonds). Within each power module the cooling plates are designed for the single IGBT (water flow), with best cooling of IGBT2, which sees ~25 K higher thermal stress. Cooling at the IGBT uses pure deionized water — 'high heat capacitance, thus lower flow (typ. 20% reduction by glycol)' as printed (slide 22).
The two power-module variants are compared side by side with their circuit diagrams (IGBT/diode pairs) and output-voltage ranges: the half-bridge power module is 'the preferred solution for cable transmission w/o OHL', switching the module output between 0 and Udc; the full-bridge power module adds DC fault-current clearing capability for OHL transmission, with an output spanning +Udc to −Udc (slide 23). Product photographs of both module generations are shown (slide 24).
In the full-bridge MMC, the DC voltage is independent from the AC voltage and can be controlled to zero or even be entirely reversed while maintaining current control on the AC and DC sides, including under short-circuit conditions (slide 25).
Full-bridge converters are presented as the most powerful and flexible solutions for transmission. Main features as printed: inherent DC turn-off capability; independent DC voltage control for load-flow control in extended DC grids and DC fault-current control; and an unlimited number of fast and smooth DC voltage recoveries after faults. The slide cites broad experience in 100 Industry and Energy applications in operation or in project execution (static frequency conversion for traction power supply and reactive power compensation), where the full-bridge MMC has been used (slide 26).
Honest-thin note: this is a technology-basics standard presentation, not a datasheet — it publishes platform headline ratings and converter-design figures only. No project- or order-specific ratings table, losses, dimensions or standards-compliance data are given for HVDC PLUS© as a product. Every quantitative figure printed in the digitized slides is collected in the table below; nothing has been added from other sources.
Guardrail omissions: the history timeline (slide 4) attaches its milestone claims to named third-party projects — the claims are kept above with the project names omitted. The reference-project slide (slide 27) is a map of 38 named HVDC PLUS© projects with in-service years; it is omitted from this entry in full per the catalog guardrail on third-party project names. The deck closes with the standard disclaimer (slide 28, © Siemens Energy 2022 boilerplate) and the publisher/contact page (slide 29: Siemens Energy Global GmbH & Co. KG, Grid Technologies, Siemensallee 11, 91058 Erlangen, Germany; for the U.S.: Siemens Energy, Inc., Gas and Power | Transmission, 15375 Memorial Drive, Suite 700, Houston, TX 77079, USA; siemens-energy.com).
| Figure (as printed) | Value | Slide |
|---|---|---|
| VSC (HVDC PLUS©) power rating | up to 2,500 MW | 3 |
| VSC with cables | up to 525 kV DC | 3 |
| VSC overhead line | up to 525 kV (800 kV) | 3 |
| LCC (HVDC Classic) power rating | up to 10,000 MW | 3 |
| LCC with cables | up to 600 kV | 3 |
| LCC overhead line | up to 1,100 kV | 3 |
| P-Q diagram range | P: −1.25 to +1.25 p.u.; Q: −1.00 to +1.00 p.u. | 8 |
| Converter double tower, 3 floors | 72 submodules | 17 |
| Converter double tower, 4 floors | 96 submodules | 17 |
| IGBT2 thermal stress margin (best-cooled position) | ~25 K higher | 22 |
| Reduction by glycol (printed: 'high heat capacitance, thus lower flow — typ. 20% reduction by glycol') | typ. 20% | 22 |
| Full-bridge experience base (Industry and Energy applications) | 100 applications in operation or in project execution | 26 |
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