MMC-HVDC Control Parameter Selection for Grid Code Compliance and Improved System Protection Performance Under AC-Side Faults

Abstract

The growing reliance on power-electronic-based renewable energy and high-voltage direct current (HVDC) systems poses challenges for distance protection, as converter fault responses differ from those of synchronous generators. At the same time, grid codes require converters to inject reactive current during AC faults, yet these requirements are typically studied independently of protection considerations. This paper addresses the gap by selecting control parameters in modular multilevel converter-based HVDC systems to enhance distance protection performance while ensuring compliance with grid codes and system stability under varying grid conditions. A global sensitivity analysis is conducted to identify the most influential control parameters, which are then systematically grouped for selection. The approach is evaluated across different system topologies and short circuit ratios, demonstrating its effectiveness in enhancing control-protection coordination and identifying the conditions where parameter tuning remains inadequate. These findings provide insights into the limitations of parameter tuning and identify scenarios where fundamental changes in control and protection may be required.