MPPT Reactive Control Algorithm for Heaving Wave Energy Converters with Power Setpoint Capabilities

Abstract

Reactive control is a popular method for maximizing wave energy absorption in wave energy converters (WECs). This technique involves adjusting the damping and stiffness coefficients of the WEC to align its natural frequency with the frequency of incoming waves. Unfortunately, wave variability and complex hydrodynamics have posed challenges in accurately determining these coefficients. This paper proposes a model-independent approach for reactive control based on a variable step size maximum power point tracking (MPPT) algorithm. The MPPT algorithm tunes the WEC's damping and stiffness coefficients toward maximum generated power. Furthermore, a power curtailment control (PCC) strategy is integrated, based on a proportional-integral (PI) controller that modifies the MPPT control force to follow power generation references below its maximum generation capacity. This capability is essential for grid integration, where power generation must match demand. Finally, a hardware-in-The-loop experimental setup was constructed to evaluate the proposed control strategies under monochromatic and polychromatic wave conditions. An analysis comparing MPPT and damping control under various polychromatic wave conditions revealed that MPPT achieves substantially higher electrical power, outperforming damping control by 55.4% to 70.6%. The experimental results demonstrated the efficacy of the PCC strategy in reducing the WEC power output to track specific power setpoints.