New Converter Solution with a Compact Modular Multilevel Structure Suitable for High-Power Medium-Voltage Wind Turbines

Modern wind turbines with increasing power levels are continuously emerging. These power levels are reaching a point where excessively high currents are obtained if the traditional low-voltage wind-turbine structure is adopted. High currents lead to excessively high losses and the need for bulky and heavy conductors to carry them. A medium-voltage structure should be a more competitive alternative to be adopted in high-power wind turbines. In this paper, a new converter solution with a modular multilevel structure suitable for driving modern/future high-power medium-voltage wind turbines is proposed. This converter topology has desirable features common to modular multilevel converters such as the improved reliability at high voltage levels, and the possibility to synthesize high-power-quality staircase-shape voltages, which leads to low requirements for harmonic and $\frac{dv}{dt}$ filters. Furthermore, the proposed converter presents reduced capacitance and inductance requirements compared to other well-established modular multilevel converter topologies, which should result in a lighter and more compact solution. The proposed solution could potentially allow for the reduction of the overall costs of the supporting structure required to withstand the weight of the wind turbine. Simulation and experimental results are presented in this paper to validate the proposed topology.