Hybrid HVDC LCC-VSC system integration and technological aspects in a multi-terminal DC grid

In the context of the ongoing energy transition, the electrical power system will undergo a significant infrastructure and management evolution. The progressive decarbonisation with decommissioning of synchronous generation units, in the face of a massive penetration from Renewable Energy Sources (RES), requires new challenges for global Transmission System Operators (TSOs). Main issues are related to a sharply decreasing inertia, lowering of short-circuit levels, reduction of voltage regulation and reactive power systems, with impact on system stability and service quality. New Voltage Sourced Converters HVDC Systems (HVDC VSC) represent an outstanding tool to drive the transformation of the electrical power system. In this paper, the feasibility of interconnecting HVDC LCC and VSC technology systems is investigated. The integration of an HVDC LCC point-to-point system in a multi-terminal network with some conversion substations in VSC technology is analysed through dynamic simulations in the MATLAB/Simulink environment. The results show how the jointly operation of the two technologies seems completely feasible in terms of control coordination, enabling the integration of large amounts RES generation in the national transmission grid adopting multi-terminal DC networks.