A Transformer-Less Compact and Light Wind Turbine Generating System for Offshore Wind Farms

Offshore wind turbines are distributed in a wide area where the power is generated usually at low voltage levels of 380 similar to 690 V. To reduce electrical power transmission losses, a low-frequency transformer is placed inside the nacelle of the offshore wind turbine to step-up the voltage up to the voltage levels of 11 similar to 33 kV. The heave weight and large size of the step-up transformer significantly increase the weight and volume of the nacelle. These penalties are critical in offshore applications, where cost of installation and regular maintenance are extremely high. As an alternative approach to achieve a compact and light offshore wind turbine a medium-voltage converter using series connected H-bridge multilevel converter topology is proposed in this paper. The transformer-less approach thus leads to a compact and environmentally friendly design, which can save large amount of installation, running and maintenance costs of offshore wind turbines. This paper mainly focuses on design and simulation of 33 kV offshore wind turbine generating system.