DC segmentation: a promising solution to improve angle stability of stressed power systems

The transmission of electricity is currently being dominated by alternating current (AC). However, direct current (DC) has seen an important development in the last decades by overcoming some of AC limitations. In particular, High Voltage Direct Current transmission based on Voltage Source Converters (VSC-HVDC) is seen as a solution to increase power transmission and facilitate the integration of renewable energy sources in power systems. In addition, with its growing share in the electrical grid, and its high controllability, VSC-HVDC systems can also help to improve power system stability. A new approach – called the DC segmentation – is to segment large AC grids into a set of asynchronously operated AC grids interconnected by HVDC links. Among others, this solution could limit the propagation of cascading outages, limit the risk of large scale blackouts, simplify market operation and improves the angle stability of the system. This paper aims to present an otherview of the work done on DC segmentation and to highlight its potential to improve angle stability in stressed power system (against large disturbances: transient stability and against small disturbances: electromechanical oscillations). The paper also illustrates the effect of DC segmentation on the stability of a power system by means of time domain simulation in a small test system.