Submission of control strategies will occur in two stages. In the first stage, strategies will be evaluated using a numerical model. For the second stage, a subset of the competitors from the first stage will be asked to submit a revised version of their controllers for implementation in a real-time control system, which will be evaluated through experimental wave tank testing on the physical system. For a detailed description of the WEC Control Competition requirements, see EWTEC paper Section 4.

Performance metrics

Applicant control strategies will be judged based on the following:

• Average extracted power.
• Capacity factor - Peak power (95% percentile) over RMS.
• Peak PTO force - The 95% percentile of PTO force.
• PTO utilisation factor - Ratio of peak PTO force and RMS PTO force.

For each of the above metrics, contestants will be ranked based on individual performance across all sea states considered. The best performing controller in each category shall receive a ranking of 1, the second-best performer shall receive a 2, and so on. Using these rankings, a final score for each contestant will be determined by a weighted sum (see EWTEC paper, Section 4).

Control strategy performance will be assessed in a series of sea states representative of the Wavestar North Sea deployment environment. Contestants will be provided with the following time-dependent states and expected to provide a control input in return.

• Position - The position of the WEC device,
• Acceleration - The acceleration of the WEC device,
• Up-wave free surface elevation - The free surface elevation will be given at 3 points up-wave from the device,
• Actuator Position - Position actuator with respect to the end stop position,
• Actuator Force - Instantaneous force exerted by the actuator on the floater.

Simulation performance

Simulation performance will be judged using the above metrics. In addition, a qualitative assessment of exceedance of any physical limits will be carried out. g. State measurements will be assumed to be perfectly accurate and contain no noise. For this stage, contestants will develop their control strategies in the same Simulink/WEC-Sim model which will be used for assessment.

Experimental performance

Experimental performance will be judged using the above metrics. The set of sea states examined will be consistent with those used in the simulation tests. State measurements will be provided directly by sensors, and will such have imperfect accuracy and some noise. Contestants will be given the specifications of the sensors utilized to obtain state measurements. For this stage, the exact dynamics of the device will not necessarily be represented by the WEC-Sim model (i.e. some model inaccuracy will be present).