Experimental Results of a DC Bus Voltage Level Control for a Load-Controlled Marine Current Energy Converter

This paper investigates three load control methods for a marine current energy converter using a vertical axis current turbine (VACT) mounted on a permanent magnet synchronous generator (PMSG). The three cases are; a fixed AC load, a fixed pulse width modulated (PWM) DC load and DC bus voltage control of a DC load. Experimental results show that the DC bus voltage control reduces the variations of rotational speed by a factor of 3.5 at the cost of slightly increased losses in the generator and transmission lines. For all three cases, the tip speed ratio (lambda) can be kept close to the expected (lambda_{opt}). The power coefficient is estimated to be 0.36 at (lambda_{opt}); however, for all three cases, the average extracted power was about (sim 19)%. A maximum power point tracking (MPPT) system, with or without water velocity measurement, could increase the average extracted power