Economic Analysis of Offshore Wind Power DC Transmission Schemes Based on Different Frequencies

Flexible direct current (DC) transmission technology is adopted to offshore wind power transmission system because it is suitable for the scenario with long transmission distance and large transmission capacity. The offshore converter station is an important part of the offshore wind power DC transmission system, which can realize rectification by modular multilevel converter (MMC) or diode rectifier unit (DRU). The power collection system of offshore wind farm can adopt power frequency or medium frequency. So, there are 4 offshore wind power DC transmission schemes. This paper calculates the cost of the whole life cycle of the offshore wind power DC transmission scheme based on MMC or DRU at the power frequency 50Hz and the medium frequency 100Hz, 150Hz and 200Hz, and compares their economic differences. This paper divides the cost of the whole life cycle into the transmission system, the equipment and the operation and maintenance part. As for the specific scenario of offshore wind power, the cost of the three parts accurately is calculated through theoretical calculation, collection of project information and simulation. Then the economic differences between the different schemes are compared and the conclusions are drawn.