Design and Evaluation of a New Converter Control Strategy for Near-Shore Tidal Turbines

While tidal stream patterns of natural channels are essentially consistent and smooth, coastal tidal flows experience much more radical speed variations. This paper proposes a new converter control strategy for maximum power extraction of the fast-changing currents that are typically seen in open waters and near the shore. The proposed method makes use of variable-speed generation and has the ability to adapt to the nature of different tidal flows, thus enabling efficient exploitation of resources that require faster dynamic responses. The main motivation behind this study has been the exploration of the possibility of combined offshore wind-tidal cogeneration. The aspects discussed in this paper include interdependences between the injection of the fluctuating generated power, grid-tie connection, and maximum power capture with a view to addressing energy conversion and power quality requirements. Detailed insights into this novel power generation system are provided with a case study that involves a method for maximum power point tracking and power injection controls in a nonstiff network.