Turbulence analysis and multiscale correlations between synchronized flow velocity and marine turbine power production

The rotor speed control unit characteristics used for the turbine regulation induces non-negligible effects on the turbine behavior under fluctuations loads. Even if the power spectrum does not reveal any scale invariance, a multiscale analysis allows us to show the correlations between the turbulence time series and the power produced. The classical Mean Square Coherency function shows that for scales larger than 10 s, the upstream velocity and power have large correlations. In the framework of the Empirical Mode Decomposition method, such correlations are studied using the time-dependence intrinsic correlation analysis method. This method allows to zoom into time-frequency scales where the flow perturbations induced some modifications in power production.