Due to the high demand of the renewable energy sources as free and clean power supplies, extracting energy from unsteady flow using marine and tidal current turbines has a distinct focusing nowadays. For their resource characteristic, extracting energy from marine/tidal current needs a simple and robust converter, in order to overcome the drawbacks of the mechanical system such as gearbox and to enhance conversion system stability. In this paper a new AC-DC-AC conversion system has been proposed. The new conversion system contains a middle stage DC-DC boost converter, which boosts the generated rectified DC voltage to be higher enough that enables the PWM inverter to generate the required voltage at the synchronized frequency. To investigate the performance of the proposed conversion system especially at low current speed compared to the conventional one, different operating conditions have been studied. Moreover, the effect of including boost converter on the total harmonic distortion (THD) has also checked. The new conversion system presents its capability to enhance and improve system performance not only at low current speed but also at high current speed.