High-voltage direct current - HVDC PLUS®

HVDC differs from traditional AC transmission by offering reduced energy losses, precise power flow control, and the ability to efficiently transmit electricity over long distances or connect grids with different frequencies.

The main components of an HVDC transmission system include converterstations, transmission lines or cables, transformers, filters, control and protection systems, reactive power compensation equipment, switchyard equipment and the core converter electronics.

Converter Stations:

Include AC/DC converters (power electronic devices housed in converter towers within the converter hall), transformers, filters, reactive power compensation equipment, and control systems.

Converting AC to DC at the sending end and DC back to AC at the receiving end.

Transmission Lines or Cables:

Carry high-voltage direct current (HVDC) power over long distances. These can be overhead lines, underground cables, or submarine cables or combined.

Transformers:

Step up or step down voltage and provide electrical isolation between the AC grid and the HVDC system.

Filters:

Eliminate harmonics to ensure clean and stable power transfer.

Reactive Power Compensation Equipment:

Maintain voltage stability and compensate for reactive power requirements of the system.

Control and Protection Systems (Brain):

Manage the operation of the HVDC system, control power flow, and protect the system against cyber attacks. Manage faults or disturbances ensure fault ride through performance.

Converter Electronics (Heart): 

manage the operation of converter technology and ensure the low-level control of power electronics devices.

Switchyard Equipment:

AIS (Air-Insulated Switchgear) or GIS (Gas-Insulated Switchgear): Used for switching, isolation, and protection in converter stations or substations.

There are two different types. Line-Commutated Converter (LCC HVDC) which uses thyristors.

Their features rely on strong AC grids and spacious footprints and need extensive harmonic filters and reactive power compensation.

Remaining use cases are long-distance bulk power transmission.

The second type are voltage source converters (VSC HVDC)

They use IGBT (insulated-gate bipolar transistor).

Their features are self-commutated and they work with weak grids. They have grid forming capabilities, compact footprint and fewer harmonics.

Use cases are the state-of-the-Art HVDC for renewable energy integration, urban/submarine systems, interconnectors and multi-terminal HVDC.

HVDC PLUS® technology by Siemens Energy is a highly flexible, efficient, and compact VSC technology platform enabling modular multilevel converters (MMC) for HVDC solutions.  Ideally suited all significant challenges in the energy landscape.

HVDC systems excel in scenarios requiring reduced losses, compact setups, and flexible control, making them ideal for modern and challenging energy transmission needs.

HVDC is the best choice for long-distance power transmission due to its efficiency and affordability. 

HVDC VSC technology plays a critical role in transitioning to a carbon-neutral energy system by enabling efficient renewable energy integration, reducing resource consumption, and supporting sustainable power transmission globally.

HVDC technology is advancing with higher efficiency, renewable energy integration, multi-terminal HVDC systems and HVDC grids, positioning it as a key enabler for a sustainable, carbon-neutral global energy system.

HVDC transmission is most cost-effective for long-distance, high-capacity power transfer, where its efficiency and ability to integrate renewable energy outweigh the initial investment in converter stations.

HVAC as a technology is widespread adopted for power transmission challenges and AC grids worldwide.

HVDC as a technology is best suited for long distance power transmissions challenges and is the ideal solution to enhance grid resilience and grid stability with advanced VSC technology and its state.-of-the-art grid forming control behavior.