Stability and control of mixed AC–DC systems with VSC‐HVDC: a review

Voltage‐source converter‐high‐voltage direct current (VSC‐HVDC) systems have become an attractive option for integrating remote and far‐from‐shore renewable energy resources to main AC grids. The desire for greater power transfer capability and the difficulty in securing right‐of‐way for new AC lines in many countries is also resulting in the increased use of embedded VSC‐HVDC systems operating in parallel with existing AC lines. It has been stated that the control and operation of VSC‐HVDC systems are of particular concern for weak grids with fewer large synchronous generation units (a highly probable case for many grids in future). If the anticipated proliferation of VSC‐HVDC links continues, several aspects of system stability will be significantly impacted. This study presents an overview of the effects of VSC‐HVDC control and operation on power system stability. The structure, control, control tuning, and modelling of VSC‐HVDC is briefly summarised to provide context for subsequent discussion of the system dynamics. An extensive critical review of the previous research into mixed AC–DC systems incorporating VSC‐HVDC is then provided including voltage stability, small and large‐disturbance angle stability, high‐frequency interaction, and frequency stability. Finally, recommendations are presented to guide critical future research.