汽轮发电机双因素非线性特性的研究

通过理论分析和有限元计算相结合的方法,以一台300MW汽轮发电机为例,对其在正常和非正常运行状态下的非线性特性曲线族和磁场分布进行了系统研究和分析,提出主要是由于铁心饱和与磁场畸变两个因素的影响,导致了汽轮发电机复杂的非线性特性.在功角相同的情况下,由于励磁电流大小不同导致的转子漏磁场的差异,影响了转子铁心的饱和,使产生相同的气隙电势Eδ时就需要不同的合成电流IΣ;而在功角较大状态下发生的磁场畸变则增长了主磁路经过气隙的部分,同样会影响合成电流产生气隙电势的大小.     

汽轮发电机不同运行条件下复杂非线性特性对比研究

以理论分析和有限元计算相结合的方法，以1台300MW汽轮发电机为例，系统研究了不同负载条件下的汽轮发电机的负载饱和特性。这些特性揭示了汽轮发电机的气隙电势与气隙合成磁势之间在不同条件下的复杂非线性关系。论文中分别对固定功率角，固定励磁电流等4种不同情况下的负载饱和特性进行了对比分析。结果表明，大部分运行条件下，由负载饱和特性决定的额定电压附近的气隙磁势都比按空载特性所决定的值大25~60%，个别情况下要大1倍以上。最后通过7.5kW模型机的实测结果验证理论分析和数值计算的正确性。     

汽轮发电机内部非线性特征的定量表述

为了建立汽轮发电机的精确的非线性模型，以有限元方法为工具，系统研究了汽轮发电机的3种非线性因素，即主磁通饱和效应、励磁电流漏磁通导致的转子轭部附加饱和效应及磁场畸变非线性。采用定、转子齿部磁压降及转子轭部磁压降在总的磁势中所占比例表示相关部分磁路饱和非线性，进而研究磁场畸变非线性的定量表示方法。提出用等效气隙长度相对于气隙设计长度的变化来描述磁场畸变非线性。在额定点附近，等效气隙长度达到设计值的1.4倍，而在临界失稳工况下，等效气隙长度达到后者的2倍以上。通过300 MW发电机实测数据与有限元计算结果对比，说明结果可信。该方法与传统方法相比，可以更准确地描述汽轮发电机非正常运行条件下的非线性程度。     

汽轮发电机非线性特征的机理及其与运行条件的关系

发电机在临界失稳等非正常运行时,会出现比正常运行条件下更复杂的非线性特征,因而为进一步建立适合电力系统分析所用的发电机非线性模型,需要研究发电机非线性特征的机理及其与运行条件的关系。以有限元方法为工具,在对不同运行条件下的非线性特征进行定量分析基础上,一一分析磁场畸变、磁路饱和等非线性特征与功角、励磁电流等运行条件之间的复杂关系。研究发现磁场畸变导致的非线性程度不仅与功角有关,还与励磁电流及电枢电流有关;励磁电流漏磁通导致的转子轭部附加饱和效应同时受到励磁电流和功角的影响;而主磁路的饱和程度取决于端电压和功角的共同作用。通过模型机实测与有限元计算结果对比,说明结论可信。     

利用功角和转速的非线性最优调速附加控制提高汽轮发电机静态和暂态稳定性的

利用实时测量的功角和转速,在原有调速系统速度反馈的基础上,提出了1种基于微分几何理论的非线性最优调速附加控制NOGAC算法。利用该算法设计的附加调速控制器进行了单机无穷大系统的低频振荡和三相短路动模实验,动模实验结果表明：NOGAC能够提高汽轮发电机的静态和暂态稳定性;在汽轮发电机发生失步故障后,投入NOGAC能够很快将发电机拉入同步;NOGAC是对调速汽门实施的1种连续平滑调节,具有优于汽门快关的调节特性。     

汽轮发电机饱和同步电抗的波动

本文以６００ＭＷ汽轮机电机为例,用有限元法计算了不同瞬时的饱和同步电抗,阐明了受饱和影响时同步电抗的波动情况。     

汽轮发电机在饱和与磁场畸变时负载励磁电流计算的新方法

磁路饱和与磁场畸变的共同作用会使发电机负载饱和特性显著偏离其空载特性,为了计算这种差异,提出了其负载励磁电流计算的一种改进方法.以300 MW汽轮发电机为例,以有限元方法为工具,获得了反映磁路饱和与磁场畸变共同作用下负载非线性特性的关系曲线族,提出了用这种新曲线族代替空载特性计算负载励磁电流的新方法.通过计算发电机在不同功角下的负载励磁电流,说明该方法比传统方法有较高的计算精度,比有限元方法有较快的计算速度.     

功角特性的同步发电机失磁静稳判据

探讨了一种新的功角特性的静稳判据。这种静稳判据,采用直测量发电机功角δ的方法,比较直观,准确,误动的可能性小,并将其与定子静稳判据和转子静判据的性能作了比较。     

发电机功角的计算及应用

阐述了发电机功率角 (以下简称功角 )重要性 ,详细介绍了功角计算方法 ,为微机发电机 -变压器故障录波装置实现对功角的监测提供了依据 ,并简要介绍了发电机 -安全运行极限图及其作用     

Analysis of turbine generator steady-state reactances for load conditions

This paper describes variations of turbine generator steady-state reactances for load conditions. When the turbine generator is of small size, magnetic saturation of the stator and rotor core is a problem. Therefore, it is important to understand the variations of the reactances for load conditions. The reactances of a 592-MVA turbine generator are calculated with d- and q-axis equations considering magnetic saturation and two-dimensional numerical magnetic field analysis. The results are as follows. (1) The equivalent synchronous reactances considering cross-magnetizing are smaller than the original synchronous reactances for load conditions. (2) Numerical values of the d- and q-axis mutual reactance and the field and q-axis mutual reactance are at their maximum when the d-axis linkage flux is nearly equal to the q-axis linkage flux under constant voltage. (3) The d-axis synchronous reactance drops with increasing reactive power under constant voltage and active power, but the q-axis synchronous reactance increases. (4) The variation of the equivalent d-axis synchronous reactance with increasing reactive power is similar to that of the d-axis synchronous reactance, but the variation of the equivalent q-axis synchronous reactance is different from that of the q-axis synchronous reactance. © 1998 Scripta Technica. Electr Eng Jpn, 123(3): 73–83, 1998     

基于风力机特性的风电机组潮流计算

在风力机特性方程和异步发电机的稳态等值模型基础上,建立了基于风力机特性的风电机组潮流计算数学模型。考虑风力机特性方程中的风力机机械力矩和发电机电磁力矩平衡,将风电机组引入处作为功率可变的PQ节点,异步发电机则作为RX等值电路模型,进行了风电机组的潮流计算。该方法引入定子电压,定子电流和转子滑差的修正量,将风力机特性方程中的风速、风能利用系数、尖速比等相关参数引入到潮流计算过程中,通过与常规的牛顿-拉夫逊潮流计算相结合,修正相应的雅可比矩阵来完成,从而保证了潮流计算迭代过程的完整性。该模型既具有传统风电机组RX模型的优点,又可以保证牛顿-拉夫逊方法的平方收敛性。最后,通过2个算例进行了潮流计算,证明了其正确性。     

Output power control of wind turbine generator by pitch angle control using minimum variance control

Effective utilization of renewable energies such as wind energy as a replacement for fossil fuels is highly desirable. Wind energy is not constant and wind generator output is proportional to the cube of the wind speed, which causes the power output of wind turbine generators (WTGs) to fluctuate. In order to reduce output power fluctuations of wind farms, this paper presents an output power leveling control strategy for wind farms based on both the mean and the standard deviation of wind farm output power, a cooperative control strategy for WTGs, and a pitch angle control method using a generalized predictive controller (GPC) intended for all operating regions of WTGs. Simulation results using an actual detailed model for wind farm systems show the effectiveness of the proposed method. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(2): 10–18, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20247     

汽轮发电机组非线性振动研究

非线性振动具有不确定性,会产生很高的振幅,具有较大的能量并会在转子上产生交变应力,对机组的安全构成重大威胁。介绍了在现场观察到的若干非线性振动现象,包括高次谐波振动、次谐波共振和基频振动的跳跃,分析了这些振动的机理、特点、产生的原因及处理措施,并对大不平衡引起的非线性振动的机理和特点作了介绍。     

发电机功角的实时计算方法

简述了发电机功角的重要性,介绍了确定发电机功角的测量法和计算法,提出一种基于同步相量测量的发电机功角计算模型,该方法利用机端电压、电流采样数据,简单、易于实现,有良好的模型适应性,可用于实时功角计算。通过仿真计算结果表明,该方法具有较好的精度,可满足工程要求。用于全网相量测量系统中,可准确监测功角动态变化,为系统的安全稳定监测提供了一定的基础。     

Influence of quadrature‐axis reactance of large turbine generator on operation

Two‐pole large generators are extensively used in power utilities. Growing demand for electric power in recent years has led to substantial increases in the capacity of generators. In line with this trend, our company has manufactured two‐pole turbine generators in the 900,000‐kVA to 1,200,000‐kVA classes. As the capacity of generators becomes larger, equivalent circuits are increasingly expected to improve their precision in estimating operation characteristics. The Park model has been widely used as an equivalent circuit model. The Park model with quadrature axis transient reactance $x_{q}^{\prime}$ is claimed to be useful for accurately estimating the load rejection characteristics of turbine generators. However, it is difficult to measure $x_{q}^{\prime}$, few studies based on measured data have appeared. As one of the few examples, we have conducted a measured data on a 500,000‐kVA‐class generator. Recently, the authors obtained test data on $x_{q}^{\prime}$ of a 900,000‐kVA‐class generator. In this study, based on these data, we studied the effect of $x_{q}^{\prime}$ using the finite element method and a transient analysis program (EMTP‐ATP). © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(3): 17–27, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21099