A novel hybrid MTDC model for optimal power flow using interior-point method

Original optimal power flow (OPF) model of hybrid multi-terminal high voltage direct current (hybrid MTDC) system ignores the converter transformer of voltage source converter (VSC). The modulation of VSC may reach the upper limit losing regulation and VSC station works in the nonlinear modulation area. This paper presents a novel model of hybrid MTDC for OPF solutions using primal-dual interior-point method (PDIPM). This new OPF model is constituted of current source converter (CSC), VSC and its coupling transformer which is considered to be a tap-changing transformer. The new model represents well both AC system and DC system where the VSC is not assumed as idealized, controllable voltage sources but com pound transformer devices which take account of VSC internal switching losses, ohmic losses and reactive power design limits. Finally, the accuracy and effectiveness of the proposed OPF model are demonstrated on a modified IEEE-14 Bus system.