HVDC circuit breakers modeling in multiterminal grids

Abstract

Transition towards sustainable energy systems lead to transformation of the existing electrical power grids. One of the key enabling technologies for this transformation is high voltage direct current (HVDC) technology that has range of advantages comparing to today’s AC systems. One of the main obstacles for HVDC grids implementation is lack of robust and reliable protection systems for DC fault clearing. HVDC circuit breaker is a crucial component for DC fault clearing, however, performance of this new technology in multiterminal HVDC grids is not fully understood. Discussed nowadays innovative hybrid circuit breaker solution, that combines mechanical switches and power electronic components, is very different from AC circuit breaker technology. Application of power electronic components for DC fault clearing puts higher requirements on protection system where approach used in AC systems may not be optimal. Alternative multifeeder protection solution is proposed and investigated in the thesis. This solution brings benefitofthe protection system cost reduction and high speed fault clearing capability. In this thesis methods for HVDC components, including converter and circuit breakers, modelling are explained. Developed models are crucial for further protection systems development and optimisation. These models are used for performance investigation of the HVDC circuit breakers in multiterminal HVDC grids, radial and meshed. Results of the simulations performed in the thesis conclude into requirements for protection system and HVDC circuit breakers design.