Development of a 300 kW horizontal-axis tidal stream energy conversion system with adaptive variable-pitch turbine and direct-drive PMSG

Abstract

The adaptation to changes in flow direction is the premise to harness the bidirectional flow energy for a tidal stream turbine. Present studies usually aim at active variable-pitch or steering with dynamic sealing to carry out this task. In this paper, a 300 kW horizontal-axis tidal stream energy conversion system with an adaptive variable-pitch turbine and an outer-rotor type PMSG is developed. Based on the BEMT, the principle of the turbine with symmetrical airfoils and backward swept blades to follow the bidirectional flow is presented, and the hydrodynamic performances, such as pitching, starting, power and thrust, are discussed. The encapsulated windings and magnets of the PMSG can expose to the seawater, and the output characteristics are analyzed at different conditions in the factory. Both the turbine and generator are characterized by no dynamic sealing. The experiment results in the field show that the bidirectional flow energy can be extracted effectively, and the generator can work well to output electric power steadily. The hydrodynamic performances predicted by the modified BEMT meet the design requirements of the 300 kW prototype. The successful field trial of this novel device lays solid support for the utilization of the bidirectional tidal stream energy.