Scaled Hardware Implementation of a Full Conversion Wind Turbine for Low Frequency AC Transmission

Low Frequency AC Transmission (LFAC) at 16.7 Hz is seen by many as a realistic cost effective alternative to VSC-HVDC for the interconnection of offshore wind. The implementation of the LFAC transmission system envisaged in this work requires the use of full conversion wind turbines which output power to a 16.7 Hz collection network, which requires some redesign of the back to back converter typically used in such turbines. This paper presents the real time scaled hardware emulation of a full conversion wind turbine connected to a 16.7 Hz grid. The study concentrates on both software control strategies for the converters, highlighting the performance of the generator for the export of power to the grid. The LFAC grid side PLL (Phase Locked Loop) is also introduced - synchronizing with the imposed 16.7 Hz. An emulation test bed is built and demonstrated in hardware - with the system successfully exporting power to the LFAC grid. This contribution highlights the ability to design a wind turbine network offshore to interface to an LFAC transmission system.