Small-scale reluctance synchronous generator variable speed wind turbine system with DC transmission linked inverters

摘要

In this paper, an alternative layout for small scale back-to-back variable speed wind turbine systems is proposed. This novel layout is created by splitting the converters at their common DC bus and linking them through the wind turbine tower with a DC rated cable. The grid-tie voltage source converter (VSC) is placed at ground level and the generator VSC is placed in the nacelle. Not only does the DC transmission cable allow electrical power to be transferred with minimal copper losses, it allows the nacelle to be more compact and maintenance friendly. The control of a reluctance synchronous generator (RSG), variable speed, fixed pitch wind turbine and grid-connected system is detailed in this paper with specific attention to the control of the DC bus voltage with a DC-link cable. DC bus voltage dynamics are investigated with practical measurements on a 3 kW wind turbine emulator, RSG and LCL-filter grid-tie system. Power input steps at rated power are used to perturb the DC bus system for two different cable lengths. Two minutes of emulated wind speed using a 150 m cable length is also tested. The results show that the DC-link dynamics are controllable.