Modelling and Stability Analysis for a Variable Speed DC Tidal/Wind Turbines with MPPT in Low Voltage DC Microgrid

DC Microgrid is a new candidate for Multi-Purpose Platforms (MPP) which highly supported by the international community for sustainably exploiting our oceans. Considering DC-systems for the MPP requires all renewable energy sources to be interfaced to a DC-bus. Wind turbines as proven developed energy for offshore use is a crucial energy source for MPP. Normally, a wind turbine in a DC-environment uses a diode rectifier for interfacing to the grid and a DC-DC boost or buck converter for extracting maximum power. Previous studies included wind turbine in a DC-microgrid did not analyze the turbine stability with wind variations. Moreover, tidal turbines, as an immature technology, are rarely considered in such DC-systems. So, this paper provides a modelling and stability analysis for a wind/tidal turbines based Permanent Magnet Synchronous Generator (PMSG). A linearized small-signal model is derived for a wind/tidal turbines based PMSG and boost converter. Two control loops are used for speed and current control. Stability analysis shows that the controller can effectively keep the system stable under wind/tidal speed variations. Simulation analysis is carried out to shows the effectiveness of the controller at various speeds considering tidal and wind turbines.