Commutation Failure analysis in single- and multi-infeed HVDC systems

Traditional methods usually use the quasi-steady state model with simplified assumptions for HVDC system analysis, which cannot take voltage distortion into account. The impact of occurrence instant of AC fault on critical commutation voltage is analytically derived and the possibility of commutation failure (CF) is analyzed. However, the complexity and nonlinearity of the single- and multi-infeed HVDC systems limit the applicability of analytical methods to study the CF phenomenon accurately. In this paper, an alternative approach that adopts electromagnetic transient simulation is proposed to assess the susceptibility of HVDC converters to CF. Two simulation-based methodologies are introduced to calculate the Commutation Failure Immunity Index (CFII). Parametric studies on the immunity of converters to commutation failure are investigated on the CIGRE benchmark HVDC test system. Finally, the proposed approach is verified by both local CF and concurrent CF phenomena, and anomalous concurrent CF phenomena are also identified in multi-infeed HVDC systems.