Introduction to HVDC Technology for Reliable Electrical Power Systems

The transmission system is becoming ever more complex. Furthermore, demand for reliable supply of electricity is growing, increasing the need for a higher level of system reliability. A solution might be to incorporate controllable power components within the system. One such component is the HVDC link. However, in the domain of reliability models for HVDC and the component\´s impact on the overall transmission system reliability, there is still much work to be done. This is an important issue in future grid planning, especially with an increasing penetration of HVDC links within synchronous transmission systems acting as "firewalls". These links may prevent disturbances propagating in the system, which is a common cause of blackouts. This paper provides a broad introduction to the HVDC technology and a literature review of reliability assessments published within this area. It gives a background to and motivation for the technology. Published reliability assessments of the HVDC technology have been reviewed and categorized. One conclusion is that a large number of models and methods for the reliability evaluation of the HVDC system itself have been published, but very few on its impact on the composite system reliability. One future challenge to be solved is how the "firewall" properties of the HVDC can be quantified in a reliability assessment.