A protection strategy for Multi-terminal HVDC (MTDC) grids based on AC/DC converters without fault handling capability such as half-bridge MMC converters is presented in this paper. The key components of the proposed strategy consist of DC breakers located at each converter station DC side and at each transmission line (overhead line or cable) end, all of them based on low-speed mechanical DC breaker technology with no fault current limiting devices.

Self-commuted Voltage Source Converter (VSC) can significantly extend the flexibility and operability of HVDC system and be used to implement the concept of Multi-Terminal HVDC (MTDC) grid. In order to take full advantage of MTDC systems, its overall behavior must be characterized in quasi static and dynamic states.

Stability is a primordial concern of power systems. From the generator point of view, it means that the machine must be able to attain an equilibrium state (possibly the pre-fault state) once the system is back to normal operation.

Stability is a primordial concern of power systems. From the generator point of view, it means that the machine must be able to attain an equilibrium state (possibly the pre-fault state) once the system is back to normal operation.

The Modular Multilevel Converter (MMC) is a most promising converter technology for the High Voltage DC application. The complex topology of the MMC requires several additional controllers to balance the energy in the capacitors which are distributed all over the converter.

The complex topology of the Modular Multilevel Converter (MMC) requires some additional controllers to keep its functionalities. One of the important requirements on the MMC control is to balance the energy stored in the distributed capacitors in the arms on the three legs.