*Article* **Investigations of Hydraulic Power Take-Off Unit Parameters Effects on the Performance of the WAB-WECs in the Different Irregular Sea States**

**Mohd Afifi Jusoh, Zulkifli Mohd Yusop, Aliashim Albani, Muhamad Zalani Daud and Mohd Zamri Ibrahim \***

Renewable Energy & Power Research Interest Group (REPRIG), Eastern Corridor Renewable Energy Special Interest Group, Faculty of Ocean Engineering Technology and Informatics, Universiti Malaysia Terengganu, Kuala Nerus 21030, Terengganu, Malaysia; mohd.afifi.jusoh@gmail.com (M.A.J.); zul\_12521@yahoo.com (Z.M.Y.); a.albani@umt.edu.my (A.A.); zalani@umt.edu.my (M.Z.D.)

**\*** Correspondence: zam@umt.edu.my; Tel.: +60-96683328

**Abstract:** Hydraulic power take-off (HPTO) is considered to be one of the most effective power take-off schemes for wave energy conversion systems (WECs). The HPTO unit can be constructed using standard hydraulic components that are readily available from the hydraulic industry market. However, the construction and operation of the HPTO unit are more complex rather than other types of power take-off, as many components parameters need to be considered during the optimization. Generator damping, hydraulic motor displacement, hydraulic cylinder and accumulator size are among the important parameters that influence the HPTO performance in generating usable electricity. Therefore, the influence of these parameters on the amount of generated electrical power from the HPTO unit was investigated in the present study. A simulation study was conducted using MATLAB/Simulink software, in which a complete model of WECs was developed using the Simscape fluids toolbox. During the simulation, each parameters study of the HPTO unit were separately manipulated to investigate its effects on the WECs performance in five different sea states. Finally, the simulated result of the effect of HPTO parameters on the amount of generated electrical power from the HPTO unit in different sea states is given and discussed.

**Keywords:** ocean wave energy; wave-activated-body; hydraulic power take-off
