20 MW-Level Offshore Wind Power Converter based on Single-Stage Hybrid Modular Multilevel Converter

With the development of offshore wind turbines towards ultra-large capacity, current wind power converter solutions face significant limitations in terms of voltage and capacity levels, efficiency, and reliability. To fully maximize the benefits of the modular multilevel converter (MMC), which offers high voltage and capacity, low losses, and low harmonics, while minimizing the need for switching devices and capacitors, this study presents a single-stage multilevel switching converter scheme specifically designed for ultra-large capacity offshore wind power converters. By utilizing an MMC topology with a wide-range adjustable DC voltage, the converter achieves both DC/DC and DC/AC conversion functions within a single stage. A hybrid MMC topology consisting of full-bridge and half-bridge submodules is adopted, allowing for a wide range of DC voltage adjustment with minimal switching device usage. The sub-module capacitance of the MMC is greatly reduced through the application of negative voltage levels. The proposed scheme has numerous advantages in terms of its economic and performance benefits. Additionally, the effectiveness and viability of the proposed topology and control strategy are validated through simulation results.