In this work, an oscillating-body wave energy converter (OBWEC) with a hydraulic power take-off (PTO) system named “Dolphin 1” is designed, in which the hydraulic PTO system is equivalent to a transfer station and plays a crucial role in ensuring the stability of the electrical energy output and the efficiency of the overall system. A corresponding mathematical model for the hydraulic PTO system has been established, the factors that influence its performance have been studied, and an algorithm for solving the optimal working pressure has been derived in this paper. Moreover, a PID control method to enable the hydraulic PTO system to automatically achieve optimal performance under different wave conditions has been designed. The results indicate that, compared with single-chamber hydraulic cylinders, double-chamber hydraulic cylinders have a wider application range and greater performance; the accumulator can stabilize the output power of the hydraulic PTO system and slightly increase it; excessively large or small hydraulic motor displacement hinders system performance; and each wave condition corresponds to a unique optimal working pressure for the hydraulic PTO system. In addition, the relationship between the optimal working pressure Pm and the pressure Ph of the wave force acting on the piston satisfies <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13344_2025_13_Article_IEq1.gif" Format="GIF" Height="33" Rendition="HTML" Resolution="72" Type="Linedraw" Width="160" /> </InlineMediaObject> <EquationSource Format="TEX">$P_{\rm{m}}^2\int_{{t_1}}^{{t_2}} {P_{\rm{h}}^2{\rm{d}}t\Big/\left({{t_2} - {t_1}} \right)}$</EquationSource> <EquationSource Format="MATHML"><math display="block"> <msubsup> <mi>P</mi> <mrow> <mrow> <mi mathvariant="normal">m</mi> </mrow> </mrow> <mn>2</mn> </msubsup> <msubsup> <mo>∫</mo> <mrow> <mrow> <msub> <mi>t</mi> <mn>1</mn> </msub> </mrow> </mrow> <mrow> <mrow> <msub> <mi>t</mi> <mn>2</mn> </msub> </mrow> </mrow> </msubsup> <mrow> <msubsup> <mi>P</mi> <mrow> <mrow> <mi mathvariant="normal">h</mi> </mrow> </mrow> <mn>2</mn> </msubsup> <mrow> <mrow> <mi mathvariant="normal">d</mi> </mrow> </mrow> <mi>t</mi> <mrow> <mo fence="true" maxsize="1.623em" minsize="1.623em" stretchy="true" symmetric="true">/</mo> </mrow> <mrow> <mo>(</mo> <mrow> <mrow> <msub> <mi>t</mi> <mn>2</mn> </msub> </mrow> <mo>−</mo> <mrow> <msub> <mi>t</mi> <mn>1</mn> </msub> </mrow> </mrow> <mo>)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>. Furthermore, adjusting the hydraulic motor displacement automatically via a PID controller ensures that the actual working pressure of the hydraulic PTO system consistently reaches or approaches its theoretically optimal value under various wave conditions, which is a very effective control method for enhancing the performance of the hydraulic PTO system.

Research on the Performance Optimization of a Hydraulic PTO System for a “Dolphin 1” Oscillating-Body Wave Energy Converter

期刊论文
发表日期：

2025年2月1日

查看全文

Wen-bin Lai,
Jia-long Li,
Si-zhang Rong,
Hong-kun Yang,
Xiong-bo Zheng

摘要

In this work, an oscillating-body wave energy converter (OBWEC) with a hydraulic power take-off (PTO) system named “Dolphin 1” is designed, in which the hydraulic PTO system is equivalent to a transfer station and plays a crucial role in ensuring the stability of the electrical energy output and the efficiency of the overall system. A corresponding mathematical model for the hydraulic PTO system has been established, the factors that influence its performance have been studied, and an algorithm for solving the optimal working pressure has been derived in this paper. Moreover, a PID control method to enable the hydraulic PTO system to automatically achieve optimal performance under different wave conditions has been designed. The results indicate that, compared with single-chamber hydraulic cylinders, double-chamber hydraulic cylinders have a wider application range and greater performance; the accumulator can stabilize the output power of the hydraulic PTO system and slightly increase it; excessively large or small hydraulic motor displacement hinders system performance; and each wave condition corresponds to a unique optimal working pressure for the hydraulic PTO system. In addition, the relationship between the optimal working pressure P_m and the pressure P_h of the wave force acting on the piston satisfies $P_{\rm{m}}^2\int_{{t_1}}^{{t_2}} {P_{\rm{h}}^2{\rm{d}}t\Big/\left({{t_2} - {t_1}} \right)}$ $P_{m}^{2} \int_{t_{1}}^{t_{2}} P_{h}^{2} d t / (t_{2} - t_{1})$ . Furthermore, adjusting the hydraulic motor displacement automatically via a PID controller ensures that the actual working pressure of the hydraulic PTO system consistently reaches or approaches its theoretically optimal value under various wave conditions, which is a very effective control method for enhancing the performance of the hydraulic PTO system.