Advanced high frequency medium voltage power architectures for wind energy systems

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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.