Experimental implementation of voltage and frequency regulation in DFIG connected to a dc-link for marine current energy conversion system

For many years, offshore wind energy and ocean currents are known as renewable energy sources with an important potential. More, for the transmission of electrical energy over long distances, high voltage direct current transmission technology is widely adopted. In this regard, this paper presents a novel DC grid connection topology for a DFIG-based marine current energy conversion system. In the proposed DFIG-DC system, a diode rectifier ensures the connection between the stator of the DFIG and the DC-link. While the rotor side and the DC-link are connected through a voltage source inverter that is the only controlled converter required in the studied system and is directly powered by the same DC-link. So, the field-oriented control strategy is adopted to regulate the DC voltage and the frequency of the DFIG DC-link system. Finally, simulation and experimental results of the studied DFIG DC-link for marine current energy conversion system are provided to show the effectiveness of DC-voltage and frequency regulation.