Wind Generator Stabilization with Doubly-Fed Asynchronous Machine

This paper investigates the function of doubly-fed asynchronous machine(DASM)with emphasis placed on its ability to the stabilization of the power system including wind generators.P(active power)and Q(reactive power)compensation from DASM can be regulated independently through secondary-excitation controlling.Simulation results by power system computer aided design(PSCAD)show that DASM can restore the wind-generator system to a normal operating condition rapidly even following severe transmission-line failures.Comparison studies have also been performed between wind turbine pitch control and proposed method.

Direct Power Control of Variable Wind Speed Based on the Doubly Fed Asynchronous Machine

In this work, the authors propose the study of a wind speed variable based on the DFAM （double fed asynchronous machine）. The model of the turbine is drawn from the classical equations describing the operation of a variable wind speed. The torque generated by the turbine is applied to the DFAM directly connected on the network side and the stator via a bidirectional converter side rotor. This configuration allows velocity variations of ±30% around the synchronous speed and the converter is then sized to one third of the rated power of the machine. The DFAM is controlled by a control vector ensuring operation of the wind turbine power coefficient maximum.

THREE-PHASE BRIDGE INVERTER FOR 9kW DOUBLY SALIENT PERMANENT MAGNET MOTOR

The three-phase bridge inverter is used as the converter topology in the power controller for a 9 kW doubly salient permanent magnet （DSPM） motor. Compared with common three-phase bridge inverters, the proposed inverter works under more complicated conditions with different principles for special winding back EMFs, position signals of hall sensors, and the given mode of switches. The ideal steady driving principles of the inverter for the motor are given. The working state with asymmetric winding back EMFs, inaccurate position signals of hall sensors, and the changing input voltage is analyzed. Finally, experimental results vertify that the given anal ysis is correct.

Harmonics in the Squirrel Cage Induction Motor Analytic Calculation-Part Ⅰ: Differential Leakage, Attenuation, Asynchronous Parasitic Torques

The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field, as well as the related differential leakage, attenuation, asynchronous parasitic torques have been discussed in great detail in the literature, but always separately, for a long time. However, systematization of the phenomenon still awaits. Therefore, it is worth summarizing the completeness of the phenomena in a single study – with a new approach at the same time-in order to reveal the relationships between them. The role of rotor slot number is emphasized much more than before. An existing, commonly used, but still impractical basic figure has been modified to more clearly demonstrate the response of the rotor for the harmonics of the stator. The need to treat differential leakage, asynchronous parasitic torques and attenuation together will be demonstrated: new formula for asynchronous parasitic torque is derived;the long-used characteristic curves for differential leakage and attenuation used separately so far was merged into one, correct curve in order to provide a correct design guide for the engineers.

New Approach to the Power Selection for Asynchronous Motor

The heating calculation of three-phase squirrel- cage asynchronous motor on the condition of starting for a prescribed rotary angle is firstly studied with time dissection method and its corresponding algorithm is provided. Then based upon the algorithm, a new method for motor power selection is established. Motor initial power determined by load power ischecked and modified in terms of time crit erion, heating criterion,and starting torque criterion.An appropriate motor power which meets three criterions is obtained at last, in the meantime, working displacement matrix andfrequency matrix used for control are acquired. Lifting motor of MDJ1800 low-level high- speed palletizer is taken as a reaI case in the paper.

Steady State Analysis of an Isolated Self-Excited Dual Three-Phase Induction Generator for Renewable Energy

In this paper modelling and analysis in autonomous mode of dual three-phase induction generator (DTPIG) with a new algorithm have been done. We develop the steady state model of a dual three-phase self-excited induction generator for stand-alone renewable generation dispensing with the segregating real and imaginary components of the complex impedance of the induction generator. The obtained admittance yields the adequate magnetizing reactance and the frequency. These two key parameters are then used to compute the self-excitation process requirements in terms of the prime mover speed, the capacitance and the load impedance on the one hand and to predict the generator steady state performance parameters on the other. Steady state performances and characteristics of different configurations are clearly examined and compared. The analytical results are found to be in good agreement with experimental results.

New-type Wound-rotor asynchronous motors Started by harmonics

Ⅰ. Preface Starting is one of the important topics of asynchronous mo-tors. Varied methods over a long period of time for improving thestarting characteristics of the asynchronous motors had beenadopted by domestic and foreign electrical engineers. The methodswhich innovate on the internal structure of the electrical motors soas to improve the starting characteristics fall into two kinds. The firstone is to change the structure of the stator winding of the motors, forinstance, the "star-delta" starting, the "prolonged side triangle"

Research on Reactive Power Optimization of Offshore Wind Farms Based on Improved Particle Swarm Optimization

The lack of reactive power in offshore wind farms will affect the voltage stability and power transmission quality of wind farms.To improve the voltage stability and reactive power economy of wind farms,the improved particle swarmoptimization is used to optimize the reactive power planning in wind farms.First,the power flow of offshore wind farms is modeled,analyzed and calculated.To improve the global search ability and local optimization ability of particle swarm optimization,the improved particle swarm optimization adopts the adaptive inertia weight and asynchronous learning factor.Taking the minimum active power loss of the offshore wind farms as the objective function,the installation location of the reactive power compensation device is compared according to the node voltage amplitude and the actual engineering needs.Finally,a reactive power optimizationmodel based on Static Var Compensator is established inMATLAB to consider the optimal compensation capacity,network loss,convergence speed and voltage amplitude enhancement effect of SVC.Comparing the compensation methods in several different locations,the compensation scheme with the best reactive power optimization effect is determined.Meanwhile,the optimization results of the standard particle swarm optimization and the improved particle swarm optimization are compared to verify the superiority of the proposed improved algorithm.

Special Problems in Pilot Protections of Transmission Lines Connecting Wind Farms

As the penetration of wind power into power grids increases,higher demands are made on the stability and protection of power systems.Unlike traditional synchronous generators,wind turbines are different on the short-circuit and impedance characteristics,thus some problems exist in pilot protections of transmission lines connecting wind farms.When a single-phase fault occurs on a transmission line,the phase selector based on current-difference sudden-change may mistake the single-phase fault for a phase-to-phase fault.This paper studies the impedance characteristics of an asynchronous wind generator,and analyzes the behavior of a fault phase selector under different conditions.Then,the paper explains that inequality between positive and negative branch coefficients is the cause for the mal-operation of the fault phase selector.Finally,some simulations are done in MATLAB to validate analysis results.

基于开口变压器法的交流电机定子非激励相绕组匝间短路检测研究

为了解决交流电机定子绕组中线圈绝缘损伤引起匝间短路故障无法准确、快速定位的问题,提出将检测转子绕组匝间短路的开口变压器法移植到检测交流电机定子绕组匝间短路,定子单相添加激励源,非激励相绕组设置故障点,开口变压器检测故障点所在槽,分析故障前后开口变压器绕组感应电动势的变化。首先阐述开口变压器检测定子非激励相的工作原理,分析正常和故障状态下通过开口变压器铁心漏磁通的表达式,进一步得到开口变压器绕组感应电动势表达式,获取故障变化规律。随后建立交流电机电磁仿真模型,进行仿真分析,最后用一台定子样机进行实验验证。结果表明:故障状态下,随着故障程度的加深,故障点所在槽的开口变压器感应电动势随之减小,证明了开口变压器可以作为离线检测交流电机定子非激励相绕组匝间短路故障的有效手段。

基于d-q变换及WOA-LSTM的异步电机定子匝间短路故障诊断方法

为了实现对异步电机定子绕组匝间短路故障的可靠在线诊断,提出一种基于d-q变换及鲸鱼优化算法(WOA)优化的长短期记忆网络(LSTM)的故障诊断方法。通过理论推导可知,d-q变换可有效提取定子电流中的特征频谱数据。采用鲸鱼优化算法对长短期记忆网络中的3个关键参数进行优化,建立WOA-LSTM故障分类模型。为了验证基于d-q变换和WOA-LSTM故障诊断方法的有效性,分别以小波变换、快速傅里叶变换及d-q变换提取电流频谱数据作为输入数据集,以一台YE2-100L1-4型异步电机为实验对象进行实验验证。研究结果表明:相比于小波变换及快速傅里叶变换,采用d-q变换能更准确的提取出定子电流中的故障特征,更精确地反映电机故障状态,有助于提高故障分类准确率;相比于传统的LSTM算法,经WOA优化后的LSTM算法分类准确率可达98.3%,能可靠地实现不同程度匝间短路故障的诊断。

紊流随机风场下多相多分裂覆冰输电导线舞动的相间闪络概率评估

针对覆冰输电导线在紊流随机风场中舞动的相间闪络问题,提出了一种多相多分裂覆冰导线舞动的相间闪络概率评估方法。首先,通过生成覆冰导线在紊流随机风场中舞动时的随机风荷载,结合多相多分裂覆冰输电导线有限元模型对紊流随机风场中的导线舞动响应进行模拟;其次,通过等价极值分布法构建了多相多分裂覆冰输电导线舞动时的相间闪络失效准则,基于概率密度演化法发展了一种多相多分裂覆冰导线在紊流随机风场中发生非同步舞动的相间闪络概率评估框架;最后,对某单跨三相四分裂覆冰输电导线算例进行分析。结果表明:1)不同相对位置的覆冰导线相间闪络概率评估结果差异明显,并且相较稳态风场情况,紊流随机风场作用下的各相导线相间闪络概率密度曲线峰值位置左移,峰值存在明显的降低;2)随着紊流度的增加,各相覆冰导线在紊流随机风场中舞动时更易发生相间闪络;3)该跨覆冰导线的相间闪络概率随平均风速的增加呈现先升后降的变化趋势,不同初始风攻角工况的各相导线相间闪络概率差异明显。

基于d-q理论的双馈异步电机定子匝间短路故障诊断方法

为实现双馈异步电机定子绕组匝间短路的早期故障诊断,提出一种基于转子电流特征频率分量的故障诊断方法 .首先,通过分析故障后电机的电磁特性,得到故障后转子电流中会产生特征频率分量的结论 .然后,通过对转子单相电流进行特殊的相移构造出三相电流,并对该组电流进行d-q变换,利用理论推导证明d-q变换后的直流分量幅值能够反映特征谐波的大小,将直流分量作为故障特征量进行双馈异步电机匝间短路故障的诊断.最后,依据有限元法建立故障前后电机的仿真模型,对不同工况下故障特征量的变化进行研究.结果表明:基于d-q理论提取的故障特征量与定子绕组的短路匝数呈正相关,且在转速变化和电压不平衡时也可有效诊断出匝间短路故障;通过设置合理的故障阈值可实现对双馈异步电机定子绕组匝间短路故障的精确辨识.研究结果可以为电机绕组匝间短路故障诊断提供参考.

异步风电机组轴系模型稳定性及参数稳定域分析

风力发电是近年来我国电力系统发展的热门领域,风电系统的稳定性的研究成为重要的课题。异步风电机组轴系模型由风力机、轴系、异步发电机等部件组成,准确分析和研究模型运行的稳定性显得尤为重要。在已有的异步风电机组五质量块轴系模型的基础上,将模型进行约化,并考虑到模型中某些运行参数在实际系统中可能是在一定范围内变化的不确定值,利用动力系统稳定性的相关理论,借助Gersgorin圆盘定理等工具,讨论当模型处于稳态时,找出不改变模型稳定性的参数稳定域的一种方法,该方法为研究含异步风电机组的电力系统的失稳问题提供了参考。最后通过算例验证了结论的有效性。

双馈异步风力发电机转子匝间短路故障振动特性分析

针对双馈异步风力发电机转子匝间短路的故障振动机理尚不明确且无法为故障诊断提供理论依据的问题,开展了双馈异步风力发电机转子匝间短路故障振动特性分析.首先,结合有限元仿真及解析推导,分析转子匝间短路下双馈异步风力发电机的气隙磁密规律,得到转子所受的不平衡磁拉力;然后,考虑转子不平衡磁拉力的情况下构建双馈异步风力发电机转子-轴承系统非线性动力学模型,利用非线性动力学仿真获取转子匝间短路故障下系统的振动仿真信号;最后,在双馈异步风力发电机故障模拟实验台上进行转子匝间短路故障实验,利用实验分析验证非线性动力学仿真结果的有效性.非线性动力学仿真及实验分析结果均表明,转子匝间短路故障下双馈异步风力发电机转子-轴承系统振动信号的频谱存在转频的谐波成分,通过检测转频的谐波分量可诊断双馈异步风力发电机转子匝间短路故障,有效揭示了双馈异步风力发电机转子匝间短路的故障振动机理.

Three-phase AC-DC Converter for Direct-drive PMSG-based Wind Energy Conversion System

In this paper,a wind energy conversion system(WECS)is presented for the electrification of rural areas with wind energy availability.A three-phase AC-DC converter based on a bridgeless Cuk converter is used for power extraction from the permanent magnet synchronous generator(PMSG).The bridgeless topology enables the elimination of the front-end diode bridge rectifier(DBR).Moreover,the converter has fewer components,simple control,and high efficiency,making it suitable for a small-scale WECS.A squirrel cage induction motor(SCIM)is used to emulate a MOD-2 wind turbine to implement the PMSG-based WECS.A direct-drive eight-pole PMSG is used in this study;thus,a low-input-voltage system is designed.The converter is designed to operate in the discontinuous inductor current mode(DICM)for inherent power factor correction(PFC)and the maximum power point tracking(MPPT)is achieved through the tip-speed ratio(TSR)following.The performance of the developed system is analyzed through simulation,and a 500 W hardware prototype is developed and tested in different wind speed conditions.

基于判据融合的异步电动机定子绕组匝间短路诊断

为解决定子绕组匝间短路故障诊断中常见异常运行工况干扰的问题,提出一种基于判据融合的异步电动机定子绕组匝间短路故障诊断方案。首先,考虑到故障特征之间的关联性,提出一种以电流特征为主、电压特征为辅的融合判据;然后,通过融合判据对定子绕组匝间短路故障及故障相进行诊断;最后,通过仿真实验证明了该方案的有效性。

基于深度学习的异步风力发电机组功率振荡抑制方法

由于引起异步风力发电机组功率振荡的因素较多,难以保障功率振荡抑制的效果,为此,提出基于深度学习的异步风力发电机组功率振荡抑制方法的研究。从风力机动态特性、发电机组动态特性以及传动链动态特性3个角度分析了异步风力发电机组功率振荡状态,借助长短期记忆网络实现对振荡的有效抑制。在测试结果中,设计的振荡抑制方法应用效果不仅更高效,且对于基础振荡幅度的控制效果更好。

大功率异步风力发电机冷却结构分析与研究

随着风电技术的发展,单机容量不断的增大,冷却结构设计、噪声性能、成本等成为电机设计中的关键环节。目前国内外对大功率异步风力发电机通风冷却结构与噪声关联性研究较少。本文以一款异步风力发电机为例,采用CFD仿真分析方法对不同结构冷却器及定、转子通风道流体场及温度场进行模拟计算和分析。研究结果表明:“M”型换热器具有降低电机内部风阻,提升内风量的效果,在满足绕组温升要求下,具有一定成本优势;同时发电机定、转子通风道错开,在一定程度上可降低电机气动噪声。通过以上分析总结,希望对异步风力发电机的冷却结构设计提供一些参考。

5.3 MW直冷双馈异步风力发电机设计与分析

直冷双馈异步风力发电机以其较好的冷却效果成为目前陆上风电领域的设计主流。设计了一款5.3 MW直冷双馈异步风力发电机,结合理论计算和仿真分析确定电机尺寸并分析电机性能。通过分析电机的磁场分布及输出电压、电流、转矩等参数验证了设计的合理性。仿真结果表明,该电机设计方案合理,可行性较高,为大功率双馈异步风力发电机的设计提供了有益的参考。