Small signal analysis of a MTDC grid with DC/DC converter integrating a DC voltage control based on a virtual resistance

The future multi-terminal direct-current (MTDC) grid will require the interconnection of point-to-point highvoltage (HV) DC links with different specifications such as DC voltage level, system grounding configuration and HVDC technology. To adapt these differences, DC/DC converters are mandatory to interconnect HVDC links. Additionally, they are capable of providing supplementary functions as they are highly controllable devices. In this paper, a primary virtual resistance DC voltage controller associated with DC/DC converter is proposed for managing DC grid voltages of the interconnected HVDC grids, increasing the reliability of the system. The commonly known topology, Front-to-Front Modular Multilevel Converter (F2FMMC) is adopted for DC/DC converter. Time-domain simulation are performed using EMTP software for validating the controller behaviour under power disturbances and large event of loss of one converter in a MMC based MTDC system. All converters are modelled using reduced order modelling (ROM) methodology. Apart from this, dynamic studies have been carried out using linear state space model for small-signal stability analysis of a HVDC system integrating DC/DC converter with virtual resistance DC voltage controller. The