Résumé

This paper investigates the efficiency difference of a double stator permanent magnet generator controlled by three vector current control strategies (maximum torque per ampere control, unity power factor control and constant flux control) in a direct drive tidal energy system. The work will focus on the tidal speed below its rated value. The rotational speed of turbine is proportional with tidal speed to maximize the power coefficient. For the same rotational speed, the generator power loss (including converter loss) is different when it is controlled by different control strategy. Through calculating the generator efficiency under the three control condition, an optimal control strategy can be chosen for special turbine rotational speed or tidal current speed.