Advanced high frequency medium voltage power architectures for wind energy systems

到2030年，风能预计将产生至少20%的全球能源需求。全球风能理事会(GWEC)预测，未来4年全球风电装机容量将增长63%。一个典型的海上风电场由数百台兆瓦级风力涡轮机和一个中压交流(MVAC)电网组成，中压交流电网从单个风力涡轮机收集电力。由于风电机组的输出电压太低，无法进行有效的长距离输电，因此每个风电机组都使用了专用的低频中压(MV)升压变压器，以将风电机组的输出电压提升到MV水平。然而，升压变压器体积大、重量重，通常位于风力涡轮机的附近。在文献中，有人建议用中压直流电网代替中压交流电网，这样就可以用中频升压功率变流器代替中压升压变压器。然而，传统的中压升压功率变流器效率低，可靠性差。对于风能系统中压功率转换所采用的现有控制器结构，将一个控制器委托给前端AC/DC阶段进行最大功率点跟踪(MPPT)，以从风电中提取最大功率；另一个控制器指定给DC/DC升压转换阶段，提供输出电压调节。因此，现有的两级中压风力发电效率低、可靠性差，需要复杂的控制结构。

By 2030, wind energy is expected to generate at least 20% of the world’s energy demand. The Global Wind Energy Council (GWEC), has forecasted that the total installed wind capacity will grow by 63% in the next 4 years. A typical offshore wind farm consists of hundreds of mega-watt wind turbines and a medium voltage AC (MVAC) grid that collects the power from the individual wind turbines. Since the output voltage of the turbine is too low for effective long distance power transmission, a dedicated low frequency medium voltage (MV) step-up transformer is used for each wind turbine to step up the turbine output voltage to the MV level. However, the step-up transformers are bulky; heavy, and typically located in the immediate vicinity of the wind turbines. In literature, the MVAC grid has been suggested to be replaced by a MV DC grid, so that the MV step-up transformers can be replaced by the MV medium frequency step-up power converters. However, the conventional MV step-up power converters have low efficiency and poor reliability. With regards to the existing controller structure used in the MV power conversion in wind energy systems, one controller is delegated to the front-end AC/DC stage for maximum power point tracking (MPPT) to extract maximum power from the wind, while another controller is designated for the DC/DC step-up voltage conversion stage to provide output voltage regulation. Therefore, the existing two-stage MV wind power conversion has low power efficiency, poor reliability and requires complex control structures.