Communication-less Protection Algorithms for Mashed VSC HVDC Cable Grids

Name: Willem Leterme

Prof. dr. ir. Dirk Van Hertem

The replacement of conventional power plants, such as coal-fired or nuclear power plants, by renewable energy sources, such as wind and photovoltaic energy, requires a new approach to the design and operation of the power system. Compared with conventional power plants, renewable energy sources have a larger geographic spread and exhibit a variable power output with limited controllability. As a consequence, the massive integration of renewable energy sources in the power system leads to larger and less predictable power flows compared with the current situation. To support these power flows, large grid reinforcements are needed in the coming years.

To transport large amounts of power over long distances, Voltage Source Converter High Voltage Direct Current (VSC HVDC), rather than the widely used ac technology, is the most suitable candidate from a technological point of view. The major grid reinforcements needed for the integration of massive amounts of renewable energy sources can be realized with large-scale meshed VSC HVDC grids.

Protection against dc side short-circuits (faults) is essential to safely and reliably operate meshed HVDC grids. The main task of the protection is, besides guaranteeing human safety, guaranteeing continuity of the system service by, e.g., preventing damage to components due to these faults. Since faults in the worst case scenarios quickly lead to overcurrents which cannot be tolerated by the sensitive power-electronic components in the system, the protection should clear faults at a high speed, typically in the order of milliseconds. In comparison with conventional ac protection, HVDC grid protection must operate ten to one hundred times faster.

This work provides the necessary concepts to develop communication-less protection algorithms for HVDC grids. These algorithms are used within HVDC grid protection to detect faults and identify the faulted line. The work gives a detailed overview of dc fault phenomena and classifies methods of fault clearing. Based on fundamental theory and reduced modeling, guidelines for fault detection methods are proposed and fast protection algorithms are developed. Besides, algorithms are developed to provide a back-up in case of failure of the protection itself. The algorithms are tailored for use in HVDC grids making use of state of the art technology. Nevertheless, the algorithms are not confined to specific systems and the applicability of the algorithms for various HVDC grids was, by contrast with existing literature, extensively investigated.

https://lirias.kuleuven.be/handle/123456789/551058

Prof. dr. ir. Dirk Van Hertem (promotor) 
Prof. dr. ir. Patrick Wollants (voorzitter/chairman) 
Prof. dr. Jef Beerten (secretaris/secretary) 
Prof. dr. ir. Ronnie Belmans 
Prof. dr. ir. Johan Suykens 
Prof. dr. Mike Barnes , University of Manchester 
Prof. dr. Bertrand Raison , Université Grenoble Alpes, ENSE3 Site AMPERE