Design, Construction and Ocean Testing of Wave Energy Conversion System with Permanent Magnet Tubular Linear Generator

In this paper, the design, construction and ocean testing of a wave energy conversion system are studied. Based on the motion characteristics of double buoys in ocean waves, a wave energy conversion system with permanent magnet tubular linear generator （PMTLG） is proposed to convert ocean wave energy into electricity. The wave energy conversion system was installed in the Yellow Sea near Lianyungang, China. The ocean test re- suits indicate that it had dynamic and static performance, and obtained an expected amount of electricity. The calcu- lation result indicates the average output power was about 1 000 W, and the conversion efficiency from wave en- ergy into electricity was 1.4%. In addition, the wireless data communication, mechanics and oceanography were also discussed.

Prediction of the Inductance in a Synchronous Linear Permanent Magnet Generator

This paper presents calculations of the varying inductances profile for a synchronous linear surface mounted permanent magnet generator in an ABC reference system. Calculations are performed by utilizing the reluctance term, known from analytic calculations and finite element method simulations. With the inductance term identified, the voltage difference between the generator’s no load and load voltage can be calculated and an external circuit can be designed for optimal use of the generator. Two different operation intervals of the linear generator are considered and the results are discussed. The result indicates that time costly finite element simulations can be replaced with simple analytical calculations for a surface mounted permanent magnet linear generator.

Magnetic field and performance analysis of a tubular permanent magnet linear synchronous motor applied in elevator door system

A novel elevator door driven by tubular permanent magnet linear synchronous motor (TPMLSM) is presented. This TPMLSM applies axial magnet array topology of the secondary rod, air-cored armature windings and slotless structure of the forcer to improve the stability of the thrust. The influence of two major dimensions, the pitch and radius of the permanent magnet (PM), on magnetic field was studied and the best values were given by the finite element analysis (FEA). The magnetic field, back EMF and thrust of the motor were analyzed and the PM size was optimized to reduce the harmonic components of the magnetic field and improve the performance of the motor. Predicted results are validated by the experiment. It is shown that the performance of the motor and the novel elevator door system is satisfying.

Current Loop Disturbance Suppression for Dual Three Phase Permanent Magnet Synchronous Generators Based on Modified Linear Active Disturbance Rejection Control

A modified four-dimensional linear active disturbance rejection control(LADRC)strategy is proposed for a dual three-phase permanent magnet synchronous generator(DTP-PMSG)system to reduce cross-coupling between the d and q axis currents in the d-q subspace and harmonic currents in the x-y subspace.In the d-q subspace,the proposed strategy uses a model-based LADRC to enhance the decoupling effect between the d and q axes and the disturbance rejection ability against parameter variation.In the x-y subspace,the 5th and 7th harmonic current suppression abilities are improved by using quasi-resonant units parallel to the extended state observer of the traditional LADRC.The proposed modified LADRC strategy improved both the steady-state performance and dynamic response of the DTP-PMSG system.The experimental results demonstrate that the proposed strategy is both feasible and effective.

Coordinated Robust PID-based Damping Control of Permanent Magnet Synchronous Generators for Low-frequency Oscillations Considering Power System Operational Uncertainties

In recent years, with the growth of wind energy resources,the capability of wind farms to damp low-frequency oscillations(LFOs) has provided a notable advantage for the stabilityenhancement of the modern power grid. Meanwhile, owingto variations in the power system operating point (OP), thedamping characteristics of LFOs may be affected adversely. Inthis respect, this paper presents a coordinated robust proportional-integral-derivative (PID) based damping control approachfor permanent magnet synchronous generators (PMSGs)to effectively stabilize LFOs, while considering power system operationaluncertainties in the form of a polytopic model constructedby linearizing the power system under a given set ofOPs. The proposed approach works by modulating the DC-linkvoltage control loop of the grid-side converter (GSC) via a supplementaryPID controller, which is synthesized by transformingthe design problem into H-infinity static output feedback(SOF) control methodology. The solution of H-infinity SOF controlproblem involves satisfying linear matrix inequality (LMI)constraints based on the parameter-dependent Lyapunov functionto ensure asymptotic stability such that the minimal H-infinityperformance objective is simultaneously accomplished forthe entire polytope. The coordinated damping controllers forthe multiple wind farms are then designed sequentially by usingthe proposed approach. Eigenvalue analysis confirms the improveddamping characteristics of the closed-loop system forseveral representative OPs. Afterward, the simulation results, includingthe performance comparison with existing approaches,validate the higher robustness of the proposed approach for awide range of operating scenarios.

Starting Control of Free Piston Stirling Linear Generator System Based on FOC

Aiming at the problem of poor system dynamic performance caused by low parameter matching in the coordinated control of Stirling engine and linear generator in the starting stage control of free piston Stirling linear generator system,a joint control method of free piston Stirling permanent magnet synchronous linear generator system based on field orientation control is proposed,based on the theoretical derivation of the mathematical model of the system and the principle of controller parameters setting,the simulation experiments of the system starting stage under several Stirling engine working conditions are carried out under simulation.The experimental results show that the stability and rapidity of the system are improved,and the dynamic response speed of generator parameters under different working conditions is accelerated,what fully verifies the correctness and effectiveness of the method.It provides an effective way to improve the control performance of the system and stabilize the power generation operation.

Robust nonlinear control via feedback linearization and Lyapunov theory for permanent magnet synchronous generator-based wind energy conversion system

In this paper,the method for the nonlinear control design of a permanent magnet synchronous generator based-wind energy conversion system(WECS)is proposed in order to obtain robustness against disturbances and harvest a maximum power from a typical stochastic wind environment.The technique overcomes both the problem of nonlinearity and the uncertainty of the parameter compared to such classical control designs based on traditional control techniques.The method is based on the differential geometric feedback linearization technique(DGT)and the Lyapunov theory.The results obtained show the effectiveness and performance of the proposed approach.

基于SOGI高频方波电压注入的永磁直线同步电机无感控制

针对永磁直线同步电机的无感控制技术,为了解决传统高频方波注入法无法准确定位转子位置和转速的问题,提出了基于SOGI高频方波电压注入的无感方法。与传统的高频方波电压注入法不同,为了得到更好的高频电流信号,采用二阶广义积分器提取响应高频电流信号,采用正交锁相环解决反正切函数没有反馈直接放大噪声的影响。为证明无感控制技术的有效性,用Simulink进行了仿真验证。结果表明,基于SOGI高频方波电压注入的无感方法大大降低了误差,缩短了调节时间,提升了响应时间。

基于平滑GMS模型和改进扩张状态观测器的复合摩擦补偿

摩擦力是影响直线伺服系统低速运行与点对点定位精度的主要非线性扰动。广义麦克斯韦(generalized Maxwellslip,GMS)摩擦模型虽然可以准确描述摩擦特性用于前馈补偿,但其存在切换点过渡时振荡的问题,同时易受测量噪声和摩擦参数变化等影响。为此,该文提出基于平滑GMS模型和改进扩张状态观测器(extended state observer,ESO)的复合摩擦补偿策略。首先,引入过渡用双曲正切函数以解决GMS模型中在切换点的反复穿越问题,并给出该模型的离线辨识方法。其次,设计基于模型信息的四阶ESO补偿剩余摩擦力与未知扰动,并引入切比雪夫滤波器整定观测器增益,以降低扰动观测与噪声敏感之间的冲突。为验证所提摩擦补偿策略的有效性,在小型高精度永磁同步直线电机定位平台上进行定位实验。实验结果验证了所提摩擦补偿策略的可行性和有效性。

基于Halbach充磁的圆筒型永磁直线发电机分析优化

为了提高波浪能发电效率,提出了一种基于Halbach充磁的圆筒型永磁直线发电机。利用有限元分析软件建立电机仿真模型,分析比较了径向充磁、轴向充磁和Halbach充磁三种不同充磁方式对气隙磁场强度及感应电动势的影响;并在Halbach充磁条件下,分别比较了不同气隙大小及永磁体厚度对气隙磁场强度的影响;通过初级两端开辅助槽和选用半开口槽的方式对电机的定位力进行了分析优化。实验结果表明,基于Halbach充磁的圆筒型永磁直线发电机与传统电机相比感应电动势幅值提高了143%,定位力幅值降低了49.3%。

基于模糊滑模控制的直驱式波浪发电装置最大功率控制方法

海洋波浪能是一种新型清洁能源,为提高直驱式波浪发电系统的发电功率和波浪能转换效率,针对目前普遍使用的比例-积分-微分(PID)控制方法存在输出纹波较大、系统稳定性较差的问题,提出基于模糊滑模控制的最大功率控制方法,根据运行状态实时调整趋近律参数,在实现最大功率跟踪的同时削弱输出纹波,减小跟踪误差,提高系统控制品质。文中以永磁直线发电机(PMLG)作为发电装置,建立系统动力学模型,并通过快速傅里叶变换方法预估不规则波浪主频,设计满足最大功率策略的期望电流跟踪曲线;在此基础上,将常规PID、滑模控制方法与所提出的模糊滑模最大功率控制方法进行仿真对比,结果表明:模糊滑模控制方法在功率上有所提升且具有更好的准确性和稳定性。

基于正交试验法的圆筒型永磁直线发电机优化设计

通过改变永磁体尺寸、比例系数以及定子齿宽等参数,分析了这些参数对发电机反电动势的影响情况,并以波形畸变率最小为目标,设计了正交优化试验,得到了上述参数的最优尺寸,所得到的仿真结果为圆筒型永磁直线发电机的设计和优化提供了理论依据。

基于冻结磁导率法的圆筒型永磁直线发电机电感参数有限元分析

圆筒型永磁直线发电机具有结构简单、能量转换效率高、可靠性好等优点,已应用于波浪能发电、直线动能吸收装置当中。将冻结磁导率法作为电机电感的求取方法,计算了电机在宽电流范围以及在负载饱和情况下电机的直轴电枢反应电感以及交轴电枢反应电感,所得到的仿真结果为圆筒型永磁直线发电机的电感计算提供了理论依据。

永磁同步直线电机的分数阶超螺旋滑模控制

为了提高永磁同步直线电机的跟踪性能,增强系统的鲁棒性,本文提出了分数阶超螺旋滑模控制策略.首先,针对外部扰动以及系统的未知状态设计广义超螺旋观测器,其能够精确估计永磁同步直线电机的速度和外部扰动.其次,将分数阶理论和终端滑模控制理论相结合,提出有限时间收敛的分数阶超螺旋滑模控制器,以实现永磁同步直线电机的跟踪控制.最后,通过仿真对比验证所提方案的有效性.

主动悬架用非均匀齿圆筒型永磁直线电机多目标分层优化设计

针对直线电机式电磁主动悬架推力波动大、推力密度低的问题,提出一种非均匀齿结构的Halbach圆筒型永磁直线电机。利用解析法对该电机的边端力模型进行推导,并进一步分析非均匀边端齿结构对电机输出性能的影响。根据分析结果选取边端齿的轴向长度和径向削短高度、永磁体高度和径向充磁的长度、内部齿的长度5个参数作为优化因子,以电机输出推力最大和推力波动最小为优化目标进行田口法和响应面法优化,得到参数的最优值。试制了原理样机并搭建了实验平台,对电机进行空载与负载实验,验证了所提结构及其设计优化方法的有效性。

用于波浪滑翔器的永磁直线发电机设计

为提高波浪滑翔器发电机的持续供电能力,设计采用波浪能为波浪滑翔器供电的圆筒型永磁直线发电机,并采用有限元法分析其性能。研究表明:圆筒型永磁直线发电机的气隙磁通密度总谐波正弦畸变率为18.8%,电压的总谐波正弦畸变率为4.1%,发电机的磁场性能与空载特性良好,可为波浪滑翔器提供高品质的电能。随外电路等效负载的增大,直线发电机的输出效率逐渐提高,在等效负载为18Ω时,直线发电机既可满足波浪滑翔器的用电需求,又能保持最大输出效率为69.25%。

单相无刷直流圆筒直线电动机及其起动推力研究

提出了一种单相无刷直流圆筒型直线电动机(SPBLDC-TLM),利用有限元方法对其电磁性能进行了分析。与三相无刷直流圆筒型直线电机对比,SPBLDC-TLM具有推力峰值大、结构简单以及成本低等优点。针对SPBLDC-TLM起动推力为零的问题,提出了斜齿和高低齿两种非对称齿结构,对比分析了两种齿结构不对称度对起动推力以及推力峰值的影响规律,为SPBLDC-TLM的起动性能优化提供了参考。结果表明,斜齿结构不对称度对起动推力影响较小,而高低齿不对称度的增大可以显著增加起动推力。采用有限元法和MATLAB软件,验证了两种非对称齿结构的有效性。

直线发电机Halbach充磁结构的改进研究

为改善传统Halbach充磁结构在直线发电机的非气隙侧产生漏磁,导致主磁通含量降低、功率密度变小和带负荷能力下降的问题,提出了在传统的Halbach充磁结构上进行改进,用于改善直线发电机的磁场分布。首先对传统矩形永磁体结构形状进行了改变,提出了梯形、T字形和U字形的Halbach充磁结构的变体,通过分析在不同尺寸下的磁通密度基波含量,从而找到各个变体的最佳设计尺寸。仿真结果表明,U字型Halbach充磁结构比其他几种结构对改善非气隙侧的漏磁作用更加明显,输出功率和效率均得到了提高。

混合叠压圆筒型永磁直线振荡电机电磁特性分析

圆筒型双定子永磁直线振荡电机因其结构简单、功率密度高而广泛应用于压缩机领域。然而,电机的定子通常采用传统的硅钢片周向叠压方式,导致其叠压系数低、磁路易饱和。因此,该文提出一种新的混合叠压方法。首先,介绍了双定子永磁直线振荡电机的基本拓扑结构和工作原理,给出磁路特有的分布方式;然后,对采用电工纯铁和硅钢片混合叠压方式进行分析,推导了硅钢片数量与电工纯铁之间的占比关系,并对不同硅钢片数量对电机反电动势、电磁推力和损耗的影响进行分析;最后,通过三维有限元分析对采用传统叠压方式和混合叠压方式的双定子永磁直线振荡电机的电磁特性进行了比较和分析。实验结果验证了混合叠压方式在提高电磁推力和简化制作工艺方面的优势。

无槽圆筒永磁直线同步电机推力波动的解析模型及抑制方法

无槽圆筒型永磁直线同步电机(slot-less tubular permanent magnet linear synchronous machine,STPMLSM)既避免了齿槽结构引起的齿槽力,又解决了初级铁心加工困难的问题,其推力波动主要来源是初级铁心端部效应和三相绕组电感不对称,介于齿槽结构与空心结构之间,推力波动的准确计算是此类电机设计与优化的关键。建立考虑初级端部效应的STPMLSM精确子域解析模型,能够快速计算空载与负载工况下的气隙磁密与推力波动,保证计算结果的准确性和高效性。基于该解析模型,提出初级铁心长度、三相绕组位置及匝数分配的综合优化方法,有效降低STPMLSM的负载推力波动,样机的推力波动从11.04%降到2.78%。最后,有限元模型和样机实验验证精确子域解析法及优化方案的正确性。