Multi-Infeed Voltage Interaction Factor: A Unified Measure of Inter-Inverter Interactions in Hybrid Multi-Infeed HVDC Systems

The multi infeed interaction factor (MIIF) index was introduced by CIGRE as a measure of inter-inverter interactions in multi-infeed HVDC systems, which include only line-commutated converter based HVDC (LCC-HVDC) links. The MIIF is although valid among LCCs in hybrid multi-infeed HVDC systems, but not among voltage-source converters (VSCs) as well as between LCC and VSC when the VSC operates under the constant ac voltage control mode. In this paper, a multi-infeed voltage interaction factor (MVIF) index is firstly proposed as the quantitative measure of inter-inverter interactions in hybrid multi-infeed HVDC systems. Compared to the MIIF, the MVIF is unified since it is applicable regardless of inverter types and control modes. Moreover, the quasi-steady-state power-flow model of hybrid multi-infeed HVDC systems is utilized as the mathematical framework to develop the analytical calculation method of the MVIF. This lends a theoretical basis for the efficient evaluation of inter-inverter interactions. Furthermore, the parametric dependence of the MVIF is analyzed to provide an exhaustive perspective of inter-inverter interactions. This offers a useful tool to aid planning and operation of hybrid multi-infeed HVDC systems. Finally, dynamic simulations conducted on the PSCAD/EMTDC program validate the MVIF and its analytical calculation method.