A new way to express the multi-infeed HVDC system and interaction factor
In multi-infeed HVDC system, the interactions and influences between DC systems and AC systems are complex as the electrical distances among DC converter stations are relatively short. Multi-infeed interaction factor (MIIF) can effectively reflect the interaction among DC systems. However, present methods to obtain the interaction factors are through simulations which are unclear in physical meaning. The paper theoretically analyzes recent analytical expressions based on impedance matrix to calculate the MIIF and proposes a new way to express the MIIF based on the admittance matrix. From both expressions, it is clear that how the equivalent impedance of AC system and coupling impedance can affect MIIF. PSCAD simulations validate the effectiveness and the correctness of the proposed expressions and some useful conclusions are drawn.