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.

Design Optimization of a Self-circulated Hydrogen Cooling System for a PM Wind Generator Based on Taguchi Method

With the continuous improvement of permanent magnet(PM)wind generators'capacity and power density,the design of reasonable and efficient cooling structures has become a focus.This paper proposes a fully enclosed self-circulating hydrogen cooling structure for a originally forced-air-cooled direct-drive PM wind generator.The proposed hydrogen cooling system uses the rotor panel supports that hold the rotor core as the radial blades,and the hydrogen flow is driven by the rotating plates to flow through the axial and radial vents to realize the efficient cooling of the generator.According to the structural parameters of the cooling system,the Taguchi method is used to decouple the structural variables.The influence of the size of each cooling structure on the heat dissipation characteristic is analyzed,and the appropriate cooling structure scheme is determined.

Winding Function Model-based Performance Evaluation of a PM Transverse Flux Generator for Applications in Direct-drive Systems

The magnetic flux in a permanent magnet transverse flux generator(PMTFG) is three-dimensional(3D), therefore, its efficacy is evaluated using 3D magnetic field analysis. Although the 3D finite-element method(FEM) is highly accurate and reliable for machine simulation, it requires a long computation time, which is crucial when it is to be used in an iterative optimization process. Therefore, an alternative to 3DFEM is required as a rapid and accurate analytical technique. This paper presents an analytical model for PMTFG analysis using winding function method. To obtain the air gap MMF distribution, the excitation magneto-motive force(MMF) and the turn function are determined based on certain assumptions. The magnetizing inductance, flux density, and back-electro-magnetomotive force of the winding are then determined. To assess the accuracy of the proposed method, the analytically calculated parameters of the generator are compared to those obtained by a 3D-FEM. The presented method requires significantly shorter computation time than the 3D-FEM with comparable accuracy.

Development and Analysis of the Magnetic Circuit on Double-Radial Permanent Magnet and Salient-Pole Electromagnetic Hybrid Excitation Generator for Vehicles

With the improvement of vehicles electrical equipment, the existing silicon rectification generator and permanent magnet generator cannot meet the requirement of the electric power consumption of the modern vehicles electrical equipment. It is di cult to adjust the air gap magnetic field of the permanent magnet generator. Consequently, the output voltage is not stable. The silicon rectifying generator has the problems of low e ciency and high failure rate.In order to solve these problems, a new type of hybrid excitation generator is developed in this paper. The developed hybrid excitation generator has a double-radial permanent magnet, a salient-pole electromagnetic combined rotor,and a fractional slot winding stator, where each rotor pole corresponds to 4.5 stator teeth. The equivalent magnetic circuit diagram of permanent magnet rotor and magnetic rotor is established. Magnetic field finite element analysis(FEA) software is used to conduct the modeling and simulation analysis on double-radial permanent magnet magnetic field, salient-pole electro-magnetic magnetic field and hybrid magnetic field. The magnetic flux density mold value diagram and vector diagram are obtained. The diagrams are used to verify the feasibility of this design. The designed electromagnetic coupling regulator controller can ensure the stable voltage export by changing the magnitude and direction of the excitation current to adjust the size of the air gap magnetic field. Therefore, the problem of output voltage instability in the wide speed range and wide load range of the hybrid excitation generator is solved.

A Novel Open-winding Permanent Magnetic Starter-generator

针对永磁电机应用于车载起动／发电系统时存在的电压调节困难、适用转速范围窄、功率因数较低等问题，提出一种新型永磁车载起动／发电系统。通过引入绕组开路型永磁电机，绕组一端接整流桥形成输出直流侧，另一端接逆变桥形成控制端，构成具有宽转速范围和高效率的永磁电机起动／发电系统。分析该系统的起动、发电一体化工作原理，给出了通过逆变侧变换器实现发电机电压、电流控制的方案。仿真和实验结果表明，该新型车载起动／发电系统具有优良的发电调压控制性能，并且适应较宽的转速范围。

新型三段Halbach永磁阵列无铁芯AFPMG设计与分析

为解决传统Halbach永磁阵列无铁芯轴向磁通永磁发电机(AFPMG)由于磁极永磁体用量增加而导致功率密度降低的问题,提出了一种变辅助磁极参数(极角和充磁夹角)的新型三段Halbach永磁阵列无铁芯AFPMG.采用三维有限元法,对新型三段Halbach永磁阵列辅助磁极极角和充磁夹角进行了多目标优化设计,从而确定了最佳辅助磁极参数.最后对比了无铁芯AFPMG中采用不同磁极结构对发电机电压波形质量和功率密度的影响.结果表明:新型永磁发电机可以使发电机电压正弦波畸变率由2.40%下降为0.44%;相较传统两段Halbach和传统三段Halbach永磁阵列的无铁芯AFPMG,新型永磁发电机功率密度得到显著提高;新型永磁发电机的永磁体用量减少了16.68%,进而减轻了转子盘质量,使发电机更加适于低风速下稳定发电.

考虑频率耦合特性的D-PMSG复数域阻抗建模及其特征分析

阻抗分析法因其简单有效被广泛用于含电力电子变换器的互联系统稳定性研究。然而,采用传统方法对频域序阻抗建模时,需通过非线性变换(Park变换及其反变换)进行坐标系转换,这会导致不同周期分量的卷积运算及相应的频移,其过程较为烦琐。针对上述问题,基于复向量时域微分算子,提出了永磁直驱同步发电机(D-PMSG)等效阻抗建模方法。该方法在时域周期系统稳定运行轨迹的邻域内直接进行小信号线性化,并采用指数旋转因子灵活反映系统受扰后的时变特性,结合时域微分算子等效表征互联系统控制环节的动态特性,避免了频域阻抗建模时坐标系的反复变换,大幅降低了解析建模的复杂度。此外,所提方法能够更加清晰地阐释互联系统受到扰动时D-PMSG并网逆变器产生频率耦合现象的物理意义;同时,能够说明基频电压初始相位对耦合分量相频特性的影响。最后,利用仿真验证了所提算法的有效性。

Design of Permanent Magnet Synchronous Generators for Wave Power Generation

In this paper, a design method for ocean wave permanent magnet synchronous generator(PMSG)is proposed with new performance criteria to obtain better output performance at the cost of less permanent magnet material. Besides, a simple equivalent analytical geometry method is put forward to calculate the sizes of permanent magnets. Based on geometric and electromagnetic models, four types of rotor structures are compared, i.e., embedded, tangential, tile surface mount and convex surface mount structures. The designs and comparisons of machine are performed with the same permanent magnet volume. Moreover, the influences of mechanical pole-arc coefficient of tile surface mount PMSG on electrical efficiency, output power, material corrosion, core loss, and torque ripple are investigated. Finite-element analysis method is applied to verify the results using Ansoft/Maxwell.

Maximum Power Point Tracking in Variable Speed Wind Turbine Based on Permanent Magnet Synchronous Generator Using Maximum Torque Sliding Mode Control Strategy

The present study was carried out in order to track the maximum power point in a variable speed turbine by minimizing electromechanical torque changes using a sliding mode control strategy. In this strategy, first, the rotor speed is set at an optimal point for different wind speeds. As a result of which, the tip speed ratio reaches an optimal point, mechanical power coefficient is maximized, and wind turbine produces its maximum power and mechanical torque. Then, the maximum mechanical torque is tracked using electromechanical torque. In this technique, tracking error integral of maximum mechanical torque, the error, and the derivative of error are used as state variables. During changes in wind speed, sliding mode control is designed to absorb the maximum energy from the wind and minimize the response time of maximum power point tracking(MPPT). In this method, the actual control input signal is formed from a second order integral operation of the original sliding mode control input signal. The result of the second order integral in this model includes control signal integrity, full chattering attenuation, and prevention from large fluctuations in the power generator output. The simulation results, calculated by using MATLAB/m-file software, have shown the effectiveness of the proposed control strategy for wind energy systems based on the permanent magnet synchronous generator(PMSG).

The Study of Optimal Structure and Value of Dump Resistance in Direct-Drive Permanent Magnet Synchronous Generators

This paper studied the direct-drive permanent magnet synchronous machine (permanent magnet synchronous generator, PMSG) Chopper optimal topology and resistance value. Compared the different Chopper circuit low voltage ride-through capability in the same grid fault conditions in simulation. This paper computes the dump resistance ceiling according to the power electronic devices and over-current capability. Obtaining the dump resistance low limit according to the temperature resistance allows, and calculating the optimal value by drop voltage in the DC-Bus during the fault. The feasibility of the proposed algorithm is verified by simulation results.

Analysis and Design of Surface Permanent Magnet Synchronous Motor and Generator

This paper presents an analytical method to design the high-efficiency surface permanent magnet synchronous motor(SPMSM)or generator(SPMSG).The air-gap and permanent magnet size can be approximately determined based on our mathematics model,which is the most important part of SPMSM design.From our method,we can know that motor’s power out torque is related to the torque angle that we selected in our design and it affects the air-gap and permanent magnet size.If we choose a low torque angle,the motor or generator’s overload power handing capability will increase.The embrace value has a vital place in designing a motor or generator due to its effects on air gap flux density,cogging torque,efficiency and so on.In order to avoid the knee effect,the working point of the permanent magnet we selected in the design should be bigger than 0.5.The developed 36 slots,4 poles,surface mound permanent generator is proposed.The corresponding finite element analysis(FEA)model is built based on our design method.Structure optimization includes stator and rotor structure size,permanent magnet size,magnetic bridge and air gap length which are analyzed and simulated by ANSYS Maxwell 2D FEA.Thermal analysis is conducted,and the housing of the alternator is designed.The alternator prototype is fabricated and tested based on our design.

Performance analysis of 20 Pole 1.5 KW Three Phase Permanent Magnet Synchronous Generator for low Speed Vertical Axis Wind Turbine

This paper gives performance analysis of a three phase Permanent Magnet Synchronous Generator (PMSG) connected to a Vertical Axis Wind Turbine (VAWT). Low speed wind condition (less than 5 m/s) is taken in consideration and the entire simulation is carried in Matlab/Simulink environment. The rated power for the generator is fixed at 1.5 KW and number of pole at 20. It is observed under low wind speed of6 m/s, a turbine having approximately1 mof radius and2.6 mof height develops 150 Nm mechanical torque that can generate power up to 1.5 KW. The generator is designed using modeling tool and is fabricated. The fabricated generator is tested in the laboratory with the simulation result for the error analysis. The range of error is about 5%-27% for the same output power value. The limitations and possible causes for error are presented and discussed.

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.

Predictive control of a chaotic permanent magnet synchronous generator in a wind turbine system

This paper investigates how to address the chaos problem in a permanent magnet synchronous generator（PMSG） in a wind turbine system. Predictive control approach is proposed to suppress chaotic behavior and make operating stable;the advantage of this method is that it can only be applied to one state of the wind turbine system. The use of the genetic algorithms to estimate the optimal parameter values of the wind turbine leads to maximization of the power generation.Moreover, some simulation results are included to visualize the effectiveness and robustness of the proposed method.

Auxiliary Teeth Design to Reduce Short-Circuit Current in Permanent Magnet Generators

In this paper,a new auxiliary teeth structure is proposed for fault-tolerant permanent magnet(PM)generators,which can reduce the short-circuit currents.Firstly,the short-circuit current and the phase to phase isolation of the fault-tolerant generator are analyzed briefly.Secondly,the auxiliary teeth structure is optimized to improve fault-tolerant capability.Then,the PM generators with different stator structures are compared to evaluate the proposed auxiliary teeth structure.Four critical generator parameters are investigated,i.e.back-electromotive forces,short-circuit currents,stator magneto motive force(MMF)harmonics,and torque performances.The results show that the proposed structure has better fault-tolerant capability than the conventional two-layer windings.Moreover,the stator MMF harmonics can be suppressed.Furthermore,the cogging torque and torque ripple can be suppressed by adopting the proposed structure.Finally,the simulated results are given to validate the theoretical analysis.

3D Magnetic Field Computation of a Permanent MagnetDisc-Type Generator Using Scalar Potential Method

The three-dimensional magnetic field of a permanent permanent (PM) disc-type generator is analyzed by the scalar potential method. In the analysis the permanent magnets are taken as magnetic charges. Hexahedron element meshes are automatically generated by a prc-proccssing program developed by the authors. The flux densily is computed by a 3D scalar potential method program. Based on the linite elcment analysis the induced emf, current, armaturc reaction effects and electromagnetic torque of the disc machine are all calculated.

基于虚拟阻抗补偿的PMSG恒导纳建模方法

永磁直驱风力发电系统结构复杂、节点数多,在进行电磁暂态实时仿真时,若采用传统建模方法会因系统导纳矩阵计算过于复杂导致仿真规模严重受限。该文提出一种基于虚拟阻抗补偿的永磁同步发电机(permanent magnet synchronous generator,PMSG)恒导纳建模方法,该方法基于传统发电机模型,通过在转子上补偿虚拟阻抗的方式使发电机导纳矩阵固定,并以暂态误差最小为目标,对阻抗参数进行优化设计;再通过结合换流器的伴随离散电路模型,可建立PMSG完整恒导纳模型并进行电磁暂态仿真,能够节省大量的计算资源。仿真试验证明,该模型具有较高的仿真精度,并且可以用于FPGA等离散化硬件仿真平台上,具有良好的适用性。

计及数字控制延时影响的含PMSG电力系统的宽频振荡z域阻抗判据研究

随着大量数字控制被应用于永磁直驱风电机组,受数字控制延时影响,含永磁直驱风电机组电力系统的宽频振荡问题日益突出。为了深入分析宽频振荡失稳机理以及快速准确地评估系统稳定性,提出了一种新的阻抗建模方法和稳定性判据。首先,基于精确离散化方法将含有延时环节的永磁直驱风电机组以及受端交流电网中的系统元件分别建模成锁相环坐标系下的z域阻抗模型。根据电路原理,将所有系统元件聚合成z域聚合阻抗模型,以此作为后续理论发展的模型基础。然后,基于盖尔圆定理,提出广义禁区判据来分析系统稳定性。最后,在Matlab/Simulink中搭建含永磁直驱风电机组的改进IEEE 3机9节点模型验证所提方法的有效性。

Design Optimization of Axial Flux Permanent Magnet (AFPM) Synchronous Machine Using 3D FEM Analysis

This paper deals with the investigation of the behavior of a low speed, dual rotor-single coreless stator, axial flux permanent magnet synchronous machine for small power applications. Firstly, with the use of nonlinear 3D FEM electromagnetic analysis, four models with different magnet topologies are designed, simulated and compared. With criteria such as output power, power factor and torque ripple, the best performing model is selected and a further investigation, regarding the effect of the disk rotor material on the behavior of the machine, is conducted. The simulation results show how the different types of commercially available steel types affect the magnetic field and the performance of the machine.

改进的广义二阶积分器的高频脉振方波电压注入PMSM无传感器控制

针对传统高频脉振方波电压注入算法的永磁同步电机(PMSM)无传感器控制系统中,使用多个滤波器来提取电流环反馈电流与高频响应电流,从而获取转子位置信息造成的系统延迟以及估计误差较大的问题,提出一种基于广义二阶积分器的无传感器控制策略。首先,与其他利用广义二阶积分器自身特性只提取高频方波响应电流检测转子位置方法不同的是,所提方法先在电流环双环控制中用广义二阶积分器对反馈基频电流信号进行提取;其次,在此控制系统的基础上,转速环用广义二阶积分器对包含电机转子位置信息的高频响应电流信号进行提取,并重新对广义二阶积分器进行了设计,在其结构上加入了高阶巴特沃斯滤波器,提高了抗谐波的衰减能力,改善了其动态性能。最后,在Simulink搭建了仿真模型并进行验证。实验结果表明,该方法相比于传统方法具有更好的动态性能和抗干扰能力。