An Optimal Power Capture Strategy for Dual-Port Direct-Drive Wave Energy Converter With Complementary Power Output

The dual-port direct-drive wave energy converter (DPDDWEC) topology has recently been proposed as a solution to address the intermittent nature of wave energy. This paper introduces an optimal frequency point (OFP) method for DPDDWEC, which can generate higher active power compared to the commonly used spectral peak frequency point (SPFP) method. The analysis reveals that DPDDWEC systems exhibit multi-degree-of-freedom characteristics due to the coupling between the dual translators, induced by the electromagnetic spring force. By establishing a comprehensive state-space model for the dual-port system and deriving the kinematic relationships between the dual translators, the resonance conditions between the system and the waves are determined, optimizing wave energy capture. Furthermore, the power output from the driven translator is effectively harnessed to compensate for the reactive power of the driver translator. The proposed OFP method produces approximately 22.2% more active power than the SPFP method under single and double-degree-of-freedom (S/DDF) conditions with different wave environments. Finally, the feasibility and effectiveness of the proposed control method for the dual-port system are validated through simulation and experiment results.