Abstract
As the development of a wave energy converter (WEC) approaches the sea trials, the handling of the power peaks becomes a more important issue. Among the various types of WECs, the oscillating-water-column (OWC) is probably the most capable to control or dissipate the excess of energy available to the power take-off (PTO) system that may occur in medium to highly energetic sea states. Two methods to limit the available pneumatic power to the turbine are: i) a relief valve installed in parallel with the turbine, and ii) a highspeed stop valve (HSSV) mounted in series with the turbine (also known in the literature as latching valve). The relief valve is a very appealing concept but the large size required to be effective deterred its application. The first generation of OWCbased devices used axial-flow turbines of Wells or impulse types. Fitting such turbines with a HSSV is a very difficult engineering challenge. The IDMEC/IST Wave Energy Group is developing a novel self-rectifying biradial turbine with a geometry that accommodates an axially sliding mechanism that operates as a HSSV. The typical stroke is less than one tenth of the rotor diameter. The paper presents a new formulation of the optimal latching control problem combined with a peak-power control. The optimal control solution is obtained within a new framework based on the Pontryagin’s Maximum Principle where the states and co-states are computed with the Discontinuous Galerkin Method.