Design of A Hydraulic Power Take-off System for the Wave Energy Device with An Inverse Pendulum

This paper describes a dual-stroke acting hydraulic power take-off （PTO） system employed in the wave energy converter （WEC） with an inverse pendulum. The hydraulic PTO converts slow irregular reciprocating wave motions to relatively smooth, fast rotation of an electrical generator. The design of the hydraulic PTO system and its control are critical to maximize the generated power. A time domain simulation study and the laboratory experiment of the full-scale beach test are presented. The results of the simulation and laboratory experiments including their comparison at full-scale are also presented, which have validated the rationality of the design and the reliability of some key components of the prototype of the WEC with an inverse pendulum with the dual-stroke acting hydraulic PTO system.

Capture Performance of A Multi-Freedom Wave Energy Converter with Different Power Take-off Systems

Among the wave energy converters (WECs), oscillating buoy is a promising type for wave energy development in offshore area. Conventional single-freedom oscillating buoy WECs with linear power take-off (PTO) system are less efficient under off-resonance conditions and have a narrow power capture bandwidth. Thus, a multi-freedom WEC with a nonlinear PTO system is proposed. This study examines a multi-freedom WEC with 3 degrees of freedom: surge, heave and pitch. Three different PTO systems (velocity-square, snap through, and constant PTO systems) and a traditional linear PTO system are applied to the WEC. A time-domain model is established using linear potential theory and Cummins equation. The kinematic equation is numerically calculated with the fourth-order Runge–Kutta method. The optimal average output power of the PTO systems in all degrees of freedom are obtained and compared. Other parameters of snap through PTO are also discussed in detail. Results show that according to the power capture performance, the order of the PTO systems from the best to worst is snap through PTO, constant PTO, linear PTO and velocity-square PTO. The resonant frequency of the WEC can be adjusted to the incident wave frequency by choosing specific parameters of the snap through PTO. Adding more DOFs can make the WEC get a better power performance in more wave frequencies. Both the above two methods can raise the WEC’s power capture performance significantly.

PTO系统阻尼参数对新型风浪能联合利用装置发电性能的影响

为了降低能源成本,提高海上风电场的发电量,提出一种新型风浪能联合利用装置,由半潜型水平轴浮式风机(HAWT)和4个环形波浪能转换器(WEC)构成,利用波浪能转换器环面和半潜平台立柱之间的相对垂荡运动来收集波浪能.综合考虑风机的控制器、波浪能转换器以及叶片上的气动载荷、平台上的水动力载荷和系泊载荷,建立该联合装置的全耦合分析模型.由于波浪能装置的PTO(power take-off)动力输出装置的阻尼参数B_(PTO)将直接决定波浪能装置的能量转换效率,因此,以北海海况为背景,分析了运行海况下4种不同参数B_(PTO)设置方案对发电性能的影响.结果表明,此种新型风机波浪能转换器联合装置可有效提高单位发电量.且当4个波浪能转换器采用参数B_(PTO)为2000(kN·s)/m的方案时,此联合装置的年发电量在4种B_(PTO)参数设置方案中最大.

Research of Power Take-off System for “Sharp Eagle Ⅱ” Wave Energy Converter

The " Sharp Eagle” device is a wave energy converter of a hinged double floating body. The wave-absorbing floating body hinges on the semi-submerged floating body structure. Under the action of wave, the wave-absorbing floating body rotates around the hinge point, and the wave energy can be converted into kinetic energy. In this paper, the power take-off system of " Sharp Eagle Ⅱ” wave energy converter (the second generation of " Sharp Eagle”) was studied, which adopts the hydraulic type power take-off system. The 0-1 power generation mode was applied in this system to make the " Sharp Eagle Ⅱ” operate under various wave conditions. The principle of power generation was introduced in detail, and the power take-off system was simulated. Three groups of different movement period inputs were used to simulate three kinds of wave conditions, and the simulation results were obtained under three different working conditions. In addition, the prototype of " Sharp Eagle Ⅱ” wave energy converter was tested on land and in real sea conditions. The experimental data have been collected, and the experimental data and simulation results were compared and validated. This work has laid a foundation for the design and application of the following " Sharp Eagle” series of devices.

Power Absorption of A Two-Body Heaving Wave Energy Converter Considering Different Control and Power Take-off Systems

This study proposed a wave power system with two coaxial floating cylinders of different diameters and drafts.Wavebob’s conceptual design has been adopted in the wave power system.In this study,a basic analysis of the wave energy extraction by the relative motion between two floats is presented.The maximum power absorption was studied theoretically under regular wave conditions,and the effects of both linear and constant damping forces on the power take-off(PTO)were investigated.A set of dynamic equations describing the floats’displacement under regular waves and different PTOs are established.A time-domain numerical model is developed,considering the PTO parameter and viscous damping,and the optimal PTO damping and output power are obtained.With the analysis of estimating the maximum power absorption,a new estimation method called Power Capture Function(PCF)is proposed and constructed,which can be used to predict the power capture under both linear and constant PTO forces.Based on this,energy extraction is analyzed and optimized.Finally,the performance characteristics of the two-body power system are concluded.

Hydraulic Power Take-off and Buoy Geometries Charac-terisation for a Wave Energy Converter

In the past few decades, world energy consumption grew considerably. Regarding this fact, wave energy should not be discarded as a valid alternative for the production of electricity. Devices suitable to harness this kind of renewable energy source and turn it into electricity are not yet commercially competitive. The work described in this paper aims to contribute to this field of research. It is focused on the design and construction of robust, simple and affordable hydraulic Power Take-Off using hydraulic commercial components.

某型船用PTI-PTO模式轴带无刷同步发电机测试

针对某型船用PTI-PTO模式轴带无刷同步发电机(轴带电机)的检测工作,制定了测试方案。通过了解轴带电机应用背景,分析其机械和电气结构特点,研究其不同模式下控制原理,在《钢质海船入级规范》相关要求的基础上,制定并优化了测试方案。优化的测试方案可执行,并验证了轴带电机能够在恒功率因数控制方式、恒压控制方式下正常运行。测试结果表明,轴带电机性能满足“规范”对电动机、发电机的相关要求。研究提出的轴带电机测试方案,对船用PTI-PTO模式电机出厂测试具有实际指导意义。

同轴双浮体波能装置参数研究

该文以同轴双浮体波能装置为研究对象,以山东省波浪场资源为背景进行条件,首先提出Matlab-APDL-AQWA联合仿真系统,实现波能-功率全过程模拟,并将模拟结果与文献中的物理模型试验数据进行对比验证。同时探究随机波浪作用下浮体半径、质量参数及PTO参数对装置获能平均功率的影响。研究表明,双浮体的半径参数和质量参数会显著影响装置的平均功率,装置获能随PTO阻尼系数的增大呈先增后减的趋势,而PTO刚度系数在一定范围内变化对装置获能影响不明显。

摆式波能发电装置PTO系统蓄能器特性研究

随着经济的发展,新能源的开发已经成为一个迫在眉睫的问题。介绍波浪能发电装置的PTO系统,通过数学计算,设计了关键装置蓄能器的研究方法;利用AMESim仿真软件对波浪能发电装置的闭式液压换能系统进行建模和仿真,仿真结果初步验证了数学方法的可靠性;并在此基础上设计了模拟实验,实验数据证明了该方法的可行性,为波浪能发电装置结构参数的优化提供参考。

基于速比调节的PTO恒转速控制策略研究

在拖拉机PTO作业过程中,由于负载变化会引起PTO转速的变化,导致作业质量下降,我们利用发动机要求转速与实际转速的差值,并结合实际转速的变化率对传动系速比进行调节,实现PTO转速的恒定输出。利用MATLAB中的Simulink模块对控制系统进行建模,通过仿真分析与实车测试,验证了控制策略的正确性与实用性。

不同动力输出系统下多浮体波浪能转换装置性能研究

[目的]旨在对一种兼具防波效果的多浮体波浪能转换装置(MBFWEC)进行动力输出系统控制优化。[方法]应用OpenFOAM程序构建数值波浪水槽,模拟5种不同PTO阻尼(线性阻尼、定常阻尼、线性弹簧阻尼、速度平方阻尼、跳跃阻尼)作用下多浮体波浪能转换装置与波浪的相互作用。同时,比较不同PTO阻尼作用下波能转换装置的能量俘获效率和消波性能。[结果]结果表明,多浮体波浪能转换装置的波浪能俘获效率最高可达52.6%,线性弹簧阻尼和跳跃阻尼作为基于线性阻尼的优化,对波浪能装置的波浪能俘获和防浪消波效果有一定程度的影响。综合考虑波浪能俘获和防浪消波作用,线性阻尼相比线性弹簧阻尼和跳跃阻尼更有优势。[结论]通过研究,找到了定常阻尼、速度平方阻尼等PTO的优势波浪区间,对多浮体的PTO阻尼设置优化有一定参考意义。

PTO系统对多节漂浮式波浪能转换装置运动和能量响应的计算分析

以双浮体铰接的多节漂浮式波浪能转换装置为研究对象,在线性波条件下计算分析了不同类型PTO系统对多浮体多自由度波浪能转换装置的运动和能量转换的影响。结果表明,在线性PTO阻尼下,装置的波浪能俘获宽度比一般随着PTO阻尼系数或回复弹簧弹性系数的增大而持续增大,在非线性PTO阻尼下,当PTO阻尼速度指数0<a≤0.75时,浮体纵摇角位移幅值随着a的增加而减小;当a>0.75时,浮体纵摇角位移基本不再发生变化。装置的波浪能俘获宽度比均随着a的增加而减小。

动力输出系统(PTO)对集成波能转换装置式防波堤消波性能及波能捕获率影响研究

针对波浪能转换装置(WEC)研究重点主要集中在能量捕获效率方面,而忽略其附带的消波功能的问题。基于OpenFOAM程序,建立垂荡浮子式波浪能发电装置与桩式约束的浮式防波堤的集成系统(OBC-FB)。主要研究WEC中的重要组件动力输出系统(PTO)对集成系统波能捕获效率及消波性能的影响。分析流体黏性影响下线性PTO系统的最优PTO阻尼特性。开发非线性电磁阻尼模型与线性PTO系统性能进行比较。结果显示,考虑黏性影响下线性的最优PTO阻尼系数略大于无黏的理论值;适当增大PTO阻尼系数可以获得更大的波能捕获宽度比(CWR),从而可以保证装置单位特征尺寸的波能转换效率更高,同时可以在更宽波况范围保证消波性能;相较于线性PTO阻尼系统,非线性电磁PTO阻尼系统可以更好地兼顾波能捕获效率和消波性能。因此,在OBC-FB集成系统的优化设计中,PTO阻尼系统是一个重要的优化参数。

基于小波变换的拖拉机PTO载荷加速编辑方法

拖拉机动力输出轴(power take-off,PTO)的作业载荷中无损伤或小损伤载荷占据大量比例,在耐久性试验中会导致试验时间过长,经济性变差,将这些载荷剔除可以得到加速载荷谱。以40马力拖拉机为研究对象,采用Daubechies小波对拖拉机PTO实测载荷信号分解并重构高频小波系数得高频小波分量,在总伪损伤保持基本一致的前提下,选取合适的阈值并结合包络线损伤判别方法,从原始载荷信号中提取损伤较大的载荷片段并拼接成加速载荷谱,分别得到压缩比为42.0%、49.8%、61.7%、62.4%、81.9%的加速载荷谱。基于频域、幅值域、统计参数和疲劳损伤等理论验证所编制加速载荷谱的正确性,以及与原始载荷谱的相似度。结果表明,加速载荷谱与原始载荷谱在伪损伤基本一致的前提下,频域、幅值域分布曲线保持相似,最值、均方根值、峰度系数等参数误差均在5%以内,对零部件造成的损伤效果也基本一致。证明该加速方法适用于拖拉机零部件加速载荷谱编制,并为农机领域加速载荷谱的编制提供参考依据。

Connection Technology of HPTO Type WECs and DC Nano Grid in Island

Wave energy fluctuating a great deal endangers the security of power grid especially micro grid in island. A DC nano grid supported by batteries is proposed to smooth the output power of wave energy converters（WECs）. Thus, renewable energy converters connected to DC grid is a new subject. The characteristics of WECs are very important to the connection technology of HPTO type WECs and DC nano grid. Hydraulic power take-off system（HPTO） is the core unit of the largest category of WECs, with the functions of supplying suitable damping for a WEC to absorb wave energy, and converting captured wave energy to electricity. The HPTO is divided into a hydraulic energy storage system（HESS） and a hydraulic power generation system（HPGS）. A primary numerical model for the HPGS is established in this paper. Three important basic characteristics of the HPGS are deduced, which reveal how the generator load determines the HPGS rotation rate. Therefore, the connector of HPTO type WEC and DC nano grid would be an uncontrollable rectifier with high reliability, also would be a controllable power converter with high efficiency, such as interleaved boost converter-IBC. The research shows that it is very flexible to connect to DC nano grid for WECs, but bypass resistance loads are indispensable for the security of WECs.

农业用拖拉机PTO现状及发展趋势

农业拖拉机是用于牵引和驱动各种配套农机具,完成农业田间作业、各种土石方工程作业、运输作业和固定作业等的动力机械。拖拉机因安装了动力输出系统,并且开发了与其配套的各种农机具,拖拉机的功能有了发展。文章介绍了拖拉机PTO的现状,并展望了拖拉机TOP的发展趋势。

电控柴油机PTO控制方法及试验研究

阐述电控柴油机PTO的功能并给出了一种控制方法,包括PTO模式使能、PTO模式退出和转速控制算法。转速控制算法采用了带前馈的闭环PID控制算法,并进行了试验验证。试验结果表明,控制方法合理,转速跟随性好且波动较小。

船用轴带电机PTO/PTI模式研究

为顺应当前节能减排的大趋势,轴带发电机已经大量应用于船上,尤其是主机功率较大的工程船。轴带电机的使用不再仅局限于发电功能(功率引出,即PTO模式),已经出现作为电动机来驱动推进器的工作模式(功率引入,即PTI模式)。介绍轴带电机PTI工作模式,尤其是验收和维护时须关注的事项。

The Method of Imbedded Lagrangian Element to Estimate Wave Power Absorption by Some Submerged Devices

A simple approach is described to estimate the wave power absorption potential of submerged devices known to cause wave focusing and flow enhancement. In particular, the presence of a flow-through power take-off （PTO） system, such as low-head turbines, can be accounted for. The wave radiation characteristics of an appropriately selected Lagrangian element （LE） in the fluid domain are first determined. In the limit of a vanishing mass, the LE reduces to a patch of distributed normal dipoles. The hydrodynamic coefficients of this virtual object are then input in a standard equation of motion where the effect of the PTO can be represented, for example, as a dashpot damping term. The process is illustrated for a class of devices recently proposed by Carter and Ertekin （2011）, although in a simplified form. Favorable wave power absorption is shown for large ratios of the LE wave radiation coefficient over the LE added mass coefficient. Under optimal conditions, the relative flow reduction from the PTO theoretically lies between 0.50 and 1 2 ≈ 0.71, with lower values corresponding to better configurations. Wave power capture widths, the sensitivity of results to PTO damping and sample spectral calculations at a typical site in Hawaiian waters are proposed to further illustrate the versatility of the method.

Application of the Latching Control System on the Power Performance of a Wave Energy Converter Characterized by Gearbox,Flywheel,and Electrical GeneratorGustavor

The latching control represents an attractive alternative to increase the power absorption of wave energy converters(WECs)by tuning the phase of oscillator velocity to the wave excitation phase.However,increasing the amplitude of motion of the floating body is not the only challenge to obtain a good performance of the WEC.It also depends on the efficiency of the power take-off system(PTO).This study aims to address the actual power performance and operation of a heaving point absorber with a direct mechanical drive PTO system controlled by latching.The PTO characteristics,such as the gear ratio,the flywheel inertia,and the electric generator,are analyzed in the WEC performance.Three cylindrical point absorbers are also considered in the present study.A wave-to-wire model is developed to simulate the coupled hydro-electro-mechanical system in regular waves.The wave energy converter(WEC)performance is analyzed using the potential linear theory but considering the viscous damping effect according to the Morison equation to avoid the overestimated responses of the linear theory near resonance when the latching control system is applied.The latching control system increases the mean power.However,the increase is not significant if the parameters that characterize the WEC provide a considerable mean power.The performance of the proposed mechanical power take-off depends on the gear ratio and flywheel.However,the gear ratio shows a more significant influence than the flywheel inertia.The operating range of the generator and the diameter/draft ratio of the buoy also influence the PTO performance.