The digest introduces a novel DC-DC converter intended for direct interface to HVDC grid from offshore wind turbines. The converter architecture consist of multiple series resonant converters feeeding multiple primaries of novel adder transformer and the secondary consist of a semi-active voltage doubler implememted by half-bridge Modular Multilevel Converter (MMC) modules. A detailed modal analysis for MMC filter design and preliminary adder transformer design principlex have been introduced in tthe digest. The converter exhibits soft-switching for all switches for every operating conditions. The experimental prototype demonstrate competetive efficiency (94.1-97.48%) for wide input voltage (34- 90V) and power range (0.15 - 0.5kW).
