Modeling and control of tidal stream converters for ocean energy conversion

Résumé

The main objective of this Ph.D. thesis is the modeling and control of a TST-based DFIG and AC-DC-AC power converter. The novel control strategy has a valuable role in order to improve all aspects of the tidal stream generator and a strong influence on the dynamic behavior of the system. This study provides evidence that operating the turbine in variable speed mode will increase the enrgy yield of the turbine by allowing it to work at its maximum power coefficient over a wide range of tidal speeds. In the case of strong tidal currents, the pitch reguoation is conceived to afford the excess power and keep the turbine oprating within the specified limits. The goals, when controlling a variable-speed TST, are optimizing the harnessed energy, regulating the generated power and reducing the mechanical loads. Therefor, it is obvious that there is a need to improve the efficiency of the studied system and the produced power potencial.