Improving the Reliability of Tidal Turbine Generator Systems

Among different ways of harnessing tidal energy, tidal stream turbines are gaining popularity over traditional tidal dams. This is owing to the lower capital cost, and potentially lower ecological impact of tidal turbines. However, compared to more developed sources of energy, tidal energy remains expensive, which impedes its large-scale utilization.

Significant reduction in the cost of energy can be achieved by reducing the maintenance expenses and improving the capacity factor. In other words, improving reliability can make tidal energy substantially cheaper. In this context, this thesis investigates a horizontal axis tidal turbine (HATT) power take-off system with a direct-drive generator.

The focus of this thesis is on improving the reliability of the electrical subsystems in the HATT power take-off system. From this perspective, power converter and generator are the two most important components in the drive train. For the converter, the reliability improvement is analyzed from the objective of delaying the thermal cycling failure in the power semiconductor modules beyond the turbine lifetime. Whereas on the generator side, a flooded generator is investigated as a potentially more reliable alternative to conventional airgap generator.