Analysis on Local and Concurrent Commutation Failure of Multi-Infeed HVDC Considering Inter-Converter Interaction

This paper provides a comprehensive analysis of local and concurrent commutation failure (CF) of Multi-Infeed HVDC scenarios considering multi-infeed interaction factor (MIIF). The literature indicates that the local CF is not influenced by MIIF, whereas our research concludes that both the local and concurrent CF are influenced by MIIF. The ability of remote converter to work under reduced reactive power enables it's feature to support local converter via inter-connection link. The MIIF measures the strength of electrical connectivity between converters. Higher MIIF gives a clearer path to remote converter to support local converter, but at the same time it provides an easy path to local converter to disturb remote converter under local fault. The presence of nearby converter increases local commutation failure immunity index (CFII) while reduces concurrent CFII. The higher MIIF cause reactive power support to flow from remote converter to local converter which reduces chances of commutation failure. A mathematical approximation to calculate increase in Local CFII for multi-infeed HVDC configurations is also proposed. A power flow approach is used to model the relation between MIIF and reactive power support from remote end. The local and concurrent CFII are found inverse to each other over MIIF; therefore, it is recommended that there is an optimal value of MIIF for all converters in close electric proximity to maintain CFII to a certain level. The numerical results of established model are compared with PSCAD/EMTDC simulations. The simulation results show the details of the influence of MIIF on local and concurrent commutation failure of Multi-Infeed HVDC, which validates the analysis presented.