Control Strategy for an Isolated DFIG Based Micro-Grid with Integrated Super-Capacitors

This paper presents a novel control strategy for isolated 4-wires Micro Grid MG based on Wind Turbine WT driven Doubly Fed Induction Generator DFIG with an integrated Super-Capacitors SCs that act as energy storage. The proposed system comprises of variable speed DFIG, DC-link and Grid Side Power Conditioner GSPC. The GSPC is devoted for the MG voltage magnitude and frequency control, balancing the load seen by the DFIG and harmonics elimination. Mixed positive and negative sequence reference frames control strategy with selective harmonic compensators is adopted to control the GSPC and to achieve high quality power supply under unbalanced and nonlinear loading conditions. The Rotor Side Voltage Source Converter RS-VSC of the DFIG is controlled to track the maximum output power from the WT and to provide the nominal reactive power of the DFIG via the rotor circuit. Two DC/DC converters are used to regulate the energy supplied/absorbed by the SCs retaining the DC side voltages of the GSPC and the RSVSC to their nominal values. Modeling and simulation of the proposed control scheme are performed using Simulink and Power System Toolboxes, Matlab. The obtained results demonstrate excellent steady state and dynamic performance under various operating conditions.