Polarity reversal inhibitor sizing criteria for meshed HVDC grids equipped with DC circuit breakers

Meshed HVDC systems, particularly those employing voltage source modular multilevel converters in half-bridge configurations, are expected to play a pivotal role in advancing future grid interoperability and strength. However, these systems require more complex protection schemes due to the inherent lack of dc short circuit interruption capability. Dc circuit breakers represent a promising solution, but require careful assessment of switching overvoltages and voltage polarity reversals phenomena. The novel device Polarity Reversal Inhibitor (PRI) aims to address these challenges. Combining both passive and power electronic components in an innovative modular structure, without the need of complex gating circuits and cooling systems, it can be easily adapted to any voltage level and system topology. In this paper, PRI's sizing criteria for the optimal operation on a 500 kV mixed dc link have been envisaged. Results confirmed that candidate devices can be selected among commercially available ones, significantly reducing the cost and footprint.