基于MRAS的双馈风力发电机无速度传感器直接转矩控制

针对速度传感器安装不方便、成本高,磁链观测对电阻依赖性强的问题,提出一种基于模型参考自适应策略的速度、电阻自适应转子磁链观测器,该观测器以转子电流和转子磁链为状态变量,应用李雅普诺夫稳定理论获得转速自适应律,实现转子转速和定子电阻辨识.建立了Matlab/Simulik环境下的双馈风力发电机无速度传感器直接转矩控制系统的仿真模型,仿真结果表明该方法可实现转子磁链的精确辨识,有效减少双馈发电机的定子电阻对系统特性的影响,提高了系统的稳定性和鲁棒性.     

基于2D暂态有限元分析的大功率超导风力发电机优化设计

为了保持较高的磁密和减小重量,海上大功率风力发电机激磁绕组由YBCO高温超导线圈构成,电枢绕组由Mg B2超导线构成,保持定子铁芯,取消转子铁芯和定子齿,超导激磁线圈和超导电枢绕组均采用非导磁材料构成,构建了10 MW超导风力发电机的模型。利用二维暂态有限元对模型进行暂态磁场的计算,得到了整个模型的磁密分布、电枢绕组的输出电流和输出电压,从而得到了整个模型的结构和电机的长度。同时对输出电压和电流进行傅里叶分析,得到电压和电流的频谱图,最后给出了10 MW超导风力发电机的整体结构。仿真结果表明:超导风力发电机的重量和成本有了较大的降低,输出电压和电流波形质量较好,谐波含有率较低。     

无刷双馈风力发电机的变速恒频最大功率跟踪

针对风力发电用变速恒频无刷双馈发电机系统,提出采用直接转矩控制方法,通过控制无刷双馈发电机的转矩和功率因数来调节其有功功率,采用最大功率因数原则设定控制绕组的磁链给定,以提高发电效率,改善电能质量,且在估计转矩时使功率绕组侧输出电压在并网前满足并网条件,以同时实现最大功率跟踪控制和变速恒频运行。此外,为了改善无刷双馈发电机直接转矩控制系统的低频性能,采用模型参考自适应辨识技术来设计控制绕组的磁链观测器,以控制绕组的电流作为比较信号,同时考虑控制绕组的电阻变化对磁链观测的影响,并利用Lyapunov稳定性定理来推导自适应率。最后通过仿真分析和实验研究验证了所提出控制方案的正确性和可行性。     

氧化锌和碳化硅组合式灭磁电阻

本文对发电机灭磁电阻的类型和特点进行了分析,并介绍了一种新型氧化锌非线性电阻和碳化硅非线性电阻组合式的非线性灭磁电阻。氧化锌和碳化硅组合式灭磁电阻是一种用于电子设备的电阻器。该电阻器的特殊设计可以有效地抑制磁场的干扰,从而提高电子设备的性能和稳定性。它由氧化锌和碳化硅两种材料组成,这两种材料的特性互补,可以在高温和高频率下保持稳定的电阻值。此外,这种电阻器还具有较小的尺寸和重量,适用于各种电子设备中的紧凑空间。     

景洪水电厂励磁系统设计及应用

为满足景洪水电厂现场应用需求,对原装进口的用于火力发电厂的GEEX2100励磁系统进行了优化设计。用SiC非线性电阻代替原有线性电阻,加快了水轮发电机灭磁速度;用开断弧压高的灭磁开关替换了原装进口的磁场开关,并增加了电气制动功能。现场测试及运行表明,该励磁系统的设计是成功的,为景洪水电厂的安全生产提供了保证。     

基于电流源型变换器的大型同步发电机励磁

将基于全控开关器件的电流源型变换器用于大型同步发电机励磁,采用正弦脉冲宽度调制(SPWM)技术控制开关状态.利用dq坐标系的间接电流控制实现对SPWM电流源型变换器功率双向流动的控制.验证了SPWM电流源型变换器带大电感负载运行的可行性.仿真试验表明,与传统可控硅励磁相比,整流时该励磁系统能向发电机端发出或吸收无功,逆变时能使励磁电流快速下降、加快励磁系统调节速度、发电机故障时实现交流灭磁.     

机械跨接器移能灭磁系统在响水涧抽水蓄能电站中的应用

以响水涧抽水蓄能电站灭磁系统为例,论述了励磁系统的主回路结构,介绍了机组正常停机和事故停机时灭磁系统动作过程及机械跨接器在灭磁过程中的动作情况,分析了磁场断路器和灭磁电阻的性能,并结合电站工程实际,从安全性和经济性出发,提出了对灭磁系统的改进建议。分析结果表明,基于机械跨接器的移能灭磁系统在各种情况下均能对发电机进行快速、可靠的灭磁。     

谐振补偿在大型发电机中性点接地中的应用

详细分析了发电机中性点经消弧线圈谐振补偿接地方式的应用原理,提出一种发电机中性点接地方式,并且与中性点经接地变压器高电阻接地方式进行比较。这种中性点接地方式可以更好地限制定子单相接地时的故障电流,从而保护了定子铁心和绕组。采用多回路分析方法对三峡左岸一种700 MW的大型发电机进行仿真计算,仿真结果表明此方法是可行的。     

基于主动阻尼器的双馈式风力发电机组故障穿越控制策略

针对双馈式风力发电机组的故障穿越控制策略问题,分析电网对称故障时其转子电压和电流的瞬态特性,找出引起转子过电压和过电流的原因。在不增加励磁系统硬件的条件下,通过改进控制方法在转子中形成一个主动阻尼电阻,有效地限制由定子磁链直流分量引起的转子过电流。以2MW双馈式风力发电机组为例,对所提出的故障穿越控制策略进行仿真研究。仿真结果说明所提出的故障穿越控制策略的可行性和有效性,可提高双馈式风力发电机机组的故障穿越能力。     

水轮发电机转子典型机电故障的不平衡磁拉力研究

针对水轮发电机发生转子偏心和转子绕组匝间短路故障产生不平衡磁拉力,进而引起机组强烈振动的情况,通过有限元仿真软件建立一台550MW水轮发电机二维仿真模型,分别对转子动、静偏心故障及转子绕组匝间短路故障进行模拟,计算各故障情况下的不平衡磁拉力,分析转子偏心程度、方向和转子绕组匝间短路程度对不平衡磁拉力大小和方向的影响。结果表明,不论是发生转子偏心故障还是发生转子绕组匝间短路故障,不平衡磁拉力数值均随故障程度的加重而增大,且不平衡磁拉力方向为诊断转子偏心方向和空载情况下匝间短路故障磁极提供帮助。研究成果为未来研究水轮发电机振动现象和故障检测奠定了基础。     

Model-Based Digital Generator Control Unit for a Variable Frequency Synchronous Generator With Brushless Exciter

This paper presents the design and implementation of a digital signal processor (DSP)-based generator control unit (GCU) for a variable frequency synchronous generator with brush-less exciter. A novel model-based control algorithm is proposed to better account for the wide operating frequency range and various load conditions. In addition to the model-based inner-loop exciter field current regulator and outer-loop generator voltage regulator, the control algorithm also adopts a generator-model-based d-axis current feed-forward loop to compensate for the load disturbance. Simulation and test results show a considerable performance improvement for the new controller when compared to the existing controllers, including better dynamics, better damping stability margin, and more uniform response over the operating range.     

Characterising the d-axis machine model of a turbogenerator usingfinite elements

An analysis of a long established fundamental assumption is presented. The assumption that superposition is valid in frequency response derived models is shown to be wrong, because eddy current losses in the solid rotor cannot be superimposed in the machine direct-axis. This implies that network theory is not valid in characterising the d-axis machine model. A machine model structure with one damper winding in the d-axis is derived from finite element analysis. Unequal mutual inductances in the machine d-axis are determined and hence the so-called differential leakage inductances are found and they are frequency dependent. The study is made on a 150 MVA turbine generator by simulating the standstill frequency response test with finite elements     

Parameter calculation of a turbogenerator during an open-circuit transient excitation

A time-domain parameter calculation of a turbogenerator state-space model is presented. The finite-element (FE) method has been used to simulate a two-dimensional (2-D) nonlinear transient condition of the turbogenerator. An open-circuit transient excitation of the machine in closed-loop conditions (excitation system and unloaded synchronous generator) was reproduced to extract flux linkages, power losses, and eddy currents produced within the generator, which allowed the computation of the parameters of an electrical circuit. An electrical circuit structure with one d-axis damper winding is proposed. New parameter behavior profiles were found for the fictitious damper winding, and the saturation effects on the field winding reactance were determined. FE commercial software is employed during the research as a validation tool. It is found that the simulated time-domain response of the lumped model closely follows the time-stepping FE model. The research was carried out for a large turbine generator of 150 MVA, 13.8 kV, 50 Hz, and two poles.     

Transient performance study of a brushless doubly fed twin stator induction generator

This paper presents theoretical, simulation, and experimental study of the brushless doubly fed twin stator induction generator (BDFTSIG) dynamics under vector control based on the orientation on the power machine stator flux. A complex transfer function is derived which links the control current and power winding current space vectors in the field coordinates. Based on this result, the transient response of the BDFTSIG to step changes in the control current is examined theoretically. The oscillatory transients are explained in detail and linked to control flux transients triggered whenever operation point of the generator is changed. Furthermore, BDFTSIG operation with closed loop control of the power machine active and reactive powers is examined theoretically and experimentally. It is shown that in the closed loop operation, the system damping may be reduced so that the PI controller gains must be properly selected to achieve a good transient response.     

Finite-element calculation of leakage inductances of a saturated salient-pole synchronous machine with damper circuits

It is important to understand the relationship between leakage flux distributions and machine characteristics for better design of synchronous machines. This paper presents a calculation method for leakage inductances of saturated salient-pole machines with damper circuits. All leakage inductances are divided into the self-leakage, gap leakage, and winding-differential leakage inductances. The leakage inductances correspond directly to the leakage flux distributions in the machines. Cross-magnetizing inductances are also calculated. The method is applied to a 300-MVA class generator. The relationship between the winding distributions, flux distributions, saturation, and inductances is discussed. Weak magnetic influence of the damper circuits on the armature in the d-axis is quantitatively illustrated through values of the winding-differential leakage inductances. The cross-magnetizing inductances, except for the d-axis damper circuits, are relatively large. Variations of the armature self-leakage inductances with saturation are small, and variations of the field and damper self-leakage inductances are larger.     

不同工况下3.3 MW永磁直驱风力发电机电磁场仿真分析及损耗修正

文章设计了一台3.3 MW外转子表贴式永磁直驱风力发电机,并对其电磁性能及短路故障情况进行了有限元仿真分析。首先,得出了这台电机在额定工况下的转矩和磁密分布等结果,以及在相间绕组短路和三相绕组短路两种情况下电机转矩、电压和电流等曲线的变化情况;然后,通过三维静磁场仿真,探究了电机定子的径向通风道结构对二维有限元仿真的影响程度,并对铁耗进行了修正;最后,通过电磁场-温度场的耦合迭代仿真,考虑了温度场影响下的电机内部材料特性的变化对电机损耗结果的影响。     

Ten MVA superconducting generator development: status at the end of1989

A progress report and some initial results from the experimental program in superconducting generators at the Massachusetts Institute of Technology (MIT) are provided The 10 MVA generator developed at MIT was to demonstrate a number of advanced concepts. These included a fully cold rotor, a cryogenic system with built-in reserves for rapid recooling following serious electrical transients, a two-stage damping and shielding system with a damping resistor tailored to good dynamic performance, a field winding structure which allows for full fault torque without straining the field winding conductors, a limited voltage gradient armature winding, and a monolithic armature structural system that provides both rigid support and good electrical isolation. The generator was completed in 1985, and experimentation has been carried out since then. The basic electrical parameters have been verified through low-level steady-state no-load and synchronous impedance tests, and sudden short-circuit and sudden open-circuit transient tests     

Methods for determining the q-axis saturation characteristics of salient-pole synchronous machines from the measured d-axis characteristics

For the accurate analysis of salient-pole synchronous machines using the two-axis frame models, the direct- (d-) and quadrature-axis (q-axis) saturation characteristics are needed. Usually, the d-axis saturation characteristics can be obtained easily by the conventional open-circuit test with the machines excited from their field winding. On the other hand, the q-axis saturation characteristics of synchronous machines cannot be measured applying simple, conventional methods, and thus, they are usually not available. In this paper, four different methods for calculating the q-axis saturation characteristics of salient-pole synchronous machines from the measured d-axis saturation characteristics are explored. In these methods, the q-axis saturation characteristics can be calculated from the readily available test data, namely the d-axis saturation characteristics and the d- and q-axis unsaturated magnetizing reactances. Finally, a comparison between these methods is made.     

负荷波动对灯泡贯流式水轮发电机转矩及损耗的影响

针对灯泡贯流式水轮发电机组负荷波动影响发电机转矩波动及转子涡流损耗的问题,以一台24 MW灯泡贯流式水轮发电机为例,利用有限元法建立了水轮发电机二维电磁场模型,并计算了发电机负载运行与空载运行时的定子绕组的电压与电流,验证了模型正确性。在此基础上,对比分析了发电机组工作在不同负荷工况下发电机的转矩脉动系数及其转子涡流损耗的差异,并得到二者随机组负荷的变化规律,揭示了机组负荷波动对发电机转子涡流损耗的影响机理,为灯泡贯流式水轮发电机的设计提供参考。     

发电电动机定子端部绕组电磁-结构耦合场计算

针对发电电动机定子端部绕组在电磁力作用下易发生故障的问题,以广州抽水蓄能电站B厂的发电电动机为例,建立了发电电动机定子端部绕组的三维模型,通过有限元法对模型电磁与结构顺序耦合进行仿真计算,得到了额定运行时电机端部绕组的应力和应变分布。结果表明,该方法能够有效地分析发电电动机定子端部绕组在电磁力作用下的应力应变分布,计算精确度比较高。