Résumé
For the integration of wind energy into the transmission system, High Voltage DC (HVDC) is the most efficient and cost-effective option. Modular multilevel converters have emerged as the most suitable converters for the required AC/DC conversions. To maintain power availability, stability, and reliability in the HVDC transmission, the converters' ability to offer fault ride-through (FRT) and work as static compensators (STATCOM) during DC faults have become important requirements. The conventional half bridge-based MMC is the most cost-effective, efficient, and widely used topology, but it cannot meet these requirements. Though full-bridge MMC has this ability, it doubles the converter cost, device count, and losses. In the present MMC topology, the capacitors occupy 50 % of the volume and 80 % weight of the converter. Reducing energy storage requirements is needed for their efficient use in offshore wind energy substations. Many Hybrid MMC (HMMC) topologies have been introduced in the last few years to offer a solution to meet these requirements, but no topology has been found yet that can fulfill all the required criteria. A comprehensive review of the existing topologies, their features, strengths, and drawbacks are needed to identify research gaps and guide future works. This paper provides a thorough and systematic review of the topology, fault handling, and STATCOM mode of all hybrid MMCs (HMMCs) for HVDC offshore wind energy transmission found in the literature. It compares these topologies' structure, losses, and functionality to guide future research. A case study calculates these topologies' losses and energy requirements by using time-domain analysis of a switching-based model in MATLAB of these converters, with a rating of 1500MVA with 1050KV DC voltage. The results present a quantitative comparison of losses and energy storage requirements across these topologies which would be useful to give directions to future works.