Abstract
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.
Highlights
Control systems for vertical axis turbines (VAT) with permanent magnet synchronous generators (PMSG) in renewable energy with an intermittent primary resource typically operate by rectifying the generator voltages and controlling the rotational speed of the turbine using the DC bus voltage
This paper reports an investigation of voltage control of the DC bus of a VAT with PMSG in a marine application
The experimental results indicate that DC bus voltage control is the best suited for marine current applications compared with a fixed pulse width modulated (PWM) or a fixed AC load
Summary
Water speed (m/s)Control systems for vertical axis turbines (VAT) with permanent magnet synchronous generators (PMSG) in renewable energy with an intermittent primary resource typically operate by rectifying the generator voltages and controlling the rotational speed of the turbine using the DC bus voltage. There are a few different ways of trying to achieve maximum power point tracking (MPPT) once the turbine has reached the nominal operation region. There is not much published in the area of control methods for VAT with PMSG in marine currents, but it has been a popular field of research the last two decades for vertical axis wind turbines (VAWT) with. Control of a VAWT with PMSG using tip speed ratio control is suggested in [4,5]. A method for finding the optimal operation point without wind speed measurement nor turbine parameters is presented in [6]. Combining MPPT and tip speed ratio control is presented in [8]
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