Last updated on Sep 12, 2024

How do you design a reliable and efficient HVDC converter station?

High voltage direct current (HVDC) transmission is a technology that can efficiently deliver large amounts of power over long distances, interconnect different grids, and integrate renewable energy sources. However, to make the most of HVDC, you need to design a reliable and efficient converter station that can convert alternating current (AC) to direct current (DC) and vice versa. In this article, you will learn the main components and functions of a HVDC converter station, the different types and topologies of converters, and the key factors and challenges that influence the design process.

1 Components and functions

A HVDC converter station consists of several components, the most important being the converter, transformer, filter, switchgear, and control and protection system. The converter is the heart of the station where AC/DC conversion takes place, either using a line-commutated converter (LCC) or a voltage-source converter (VSC), depending on the technology and application. The transformer steps up or steps down the AC voltage level and isolates the converter from the AC grid. The filter reduces any harmonics and reactive power generated by the converter to improve power quality and stability of the system. The switchgear protects and controls the converter and other components from faults and overloads. Lastly, the control and protection system monitors and regulates operation of the station while coordinating with other stations in the HVDC link.

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Venkatesh Meriga

Electrical Engineer || ETAP || AUTOCAD || SBIT'23
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Component Selection: Use high-quality thyristors or IGBTs for reliable rectification and inversion. Cooling Systems: Implement effective cooling solutions to manage heat dissipation in converters and transformers. HVDC Circuit Breakers: Integrate to protect against faults and enable rapid system isolation. Control Systems: Deploy advanced control algorithms for precise voltage and current regulation. Transformer Design: Use appropriately rated transformers to handle high voltages and ensure minimal losses. Grounding and Insulation: Design robust grounding and insulation systems to prevent electrical faults and ensure safety Monitoring and Diagnostics: Install real-time monitoring for early fault detection and system health assessment.

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2 Converter types and topologies

There are two main types of converters for HVDC applications: LCC and VSC. LCCs are based on thyristors, which are switched on by external signals and switched off by the AC grid voltage. LCCs are cheaper and more efficient than VSCs, but they require a strong AC grid to operate, they produce more harmonics and reactive power, and they cannot control the DC voltage independently. VSCs are based on self-commutated devices, such as insulated-gate bipolar transistors (IGBTs), which can be switched on and off by internal signals. VSCs can operate with weak or isolated AC grids, they produce less harmonics and reactive power, and they can control the DC voltage independently. However, VSCs are more expensive and less efficient than LCCs, and they have lower power ratings and higher losses.

Within each type of converter, there are different topologies that affect the performance and cost of the converter station. For example, LCCs can be arranged in a 12-pulse or 24-pulse configuration, which reduces the harmonics and increases the power transfer capability. VSCs can be arranged in a two-level or a multilevel configuration, which reduces the switching losses and the voltage stress on the devices. The choice of the converter type and topology depends on the technical and economic requirements of the HVDC project.

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3 Design factors and challenges

When designing a HVDC converter station, many factors and challenges need to be addressed. Power rating and voltage level are two of the main ones- higher power ratings and voltage levels require more expensive converters, transformers, filters, and switchgear, but they reduce the losses and current in the line. Additionally, grid characteristics and compatibility must be taken into account to ensure the stability and reliability of the converter station and HVDC link. Environmental and social impacts should also be considered for sustainability and acceptability of the converter station and project- this includes minimizing noise, electromagnetic interference, land use, visual impact, greenhouse gas emissions, as well as complying with regulations and standards of the host country.

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4 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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How do you design a reliable and efficient HVDC converter station?

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1 Components and functions

2 Converter types and topologies

3 Design factors and challenges

4 Here’s what else to consider

Power Systems

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