HVDC link interconnections under construction or planned in France are part of a highly meshed ac network. This is a relatively new operating condition. The impact of their operation and the risk of abnormal interaction may have an influence on the ac network. The use of voltage source converters (VSCs) with the modular multilevel converter (MMC) topology is becoming more attractive mainly due to their higher performances and lower cost. This paper analyses the operation and interaction of MMC–HVDC links embedded in an ac grid. First a MMC–HVDC link model suitable for small-signal analysis is presented. This small-signal HVDC model is then validated against an EMT-type model for ac systems having different SCR (Short-Circuit Ratio) values. Modal analysis and parametric studies are performed in order to study the impact of an ac line connected in parallel with an HVDC link.