Integrated AC/DC model for power system stability studies

A generic method is proposed in this paper to integrate VSC terminals into AC systems taking into account the cascaded VSC control structure. The method allows the VSC models to be developed separately by considering them as current injections into the connected AC system, and therefore provides an alternative for quickly integrating new VSC models into conventional power system models. The method can also be applied to Multi-Terminal DC (MTDC) grid integration provided with an available AC/DC load flow. The integrated system model developed based on this method is suitable for small signal analysis and controller designs. Modal analysis techniques can be readily applied to the whole integrated AC/DC model and the effects of VSC controls on the AC system power oscillations can be analysed mathematically.