Due to highly demand on the renewable energy sources as a free and a clean power resource, extracting energy from unsteady flow using marine and tidal current turbines has a special focusing nowadays. For their resource characteristic, extracting energy from them needs more simple and robust converter in order to avoid the drawbacks of the mechanical system such as gearbox and makes the marine/tidal current energy more reliable. The required AC-DC-AC conversion system equipped with DC-DC boost converter has been designed. To investigate the efficient performance of that conversion system especially at low current speed, different operating conditions were studied; the system was tested with/without boost converter at different current speeds operation. Moreover, the effect of including boost converter on the total harmonic distortion THD is checked.