Connection schemes for offshore power generation with an internal collection grid include a power generation system which includes a plurality of generator-rectifier subsystems. The scheme further includes a medium voltage DC (MVDC) collection network with positive pole cables and negative pole cables connected to the DC outputs of the generator-rectifier subsystems. At least one offshore substation includes a positive bus bar and a negative bus bar correspondingly connected to the positive pole cables and negative pole cables of the MVDC collection network and a plurality of main DC-DC converters. Each main DC-DC converter includes multiple modules connected to the MVDC bus bars and each module has a positive and a negative output such that the modules' outputs are serially connected to one another. The schemes may also include a high voltage DC (HVDC) transmission system connected to the modules' outputs and at least one DC/AC converter at an onshore substation.