Research on Hybrid HVDC Transmission System for Large-Scale All-DC Offshore Wind and Solar Energies

With the continuous growth of offshore new energy, efficient and reliable DC transmission of offshore new energy has gradually become a hot topic of recent attention. This article proposes a novel topology structure for large-scale offshore wind and solar DC power grids. The photovoltaic and wind power generation units with independent input and series output use dual active bridge submodules to complete energy conversion, and the power balance of the submodules is achieved through power balancing units to achieve stable energy output. The generator set outputs DC and sends it to the DC bus, which is then connected to a modular multi-level MMC DC transformer for boosting to the transmission level. After that, it is converted into AC through an onshore converter station and sent to the onshore power grid. We have established a simulation model for the topology and verified through simulation experiments that the proposed topology structure has good reliability and can meet the requirements of large-scale wind and solar energy gathering and transmission systems.