Effect of piecewise damping torques and coefficients on power absorption of a point-absorber wave energy converter

Wave energy converters (WECs), especially point-absorber WECs, are of great interest in recent years due to the global energy crisis. The power take-off (PTO) control strategy plays a crucial role in the motion response and power absorption of the WEC. This study investigates a WEC on a multi-float power generation platform as a case study, and compares four different control strategies. These control strategies are classified into two types based on the method of generating PTO damping: Type-A, which applies damping torque, and Type-B, which applies damping coefficient. Furthermore, each type has two subtypes: continuous and piecewise, depending on whether the damping torque or coefficient is continuous in the upward and downward motions of the WEC. The results indicate that the Type-B control strategy improves the power quality compared with the Type-A control strategy. Among the subtypes, the piecewise control strategy achieves greater power absorption than the continuous control strategy, while keeping the motion performance at an acceptable level.