A novel adaptive backstepping design of turbine main steam valve control

The problem of transient stability for a single machine infinite bus system with turbine main steam valve control is addressed by means of a novel adaptive backstepping method in this paper.The recursive design procedure of the proposed controller is much simpler than that of the existing controller based on conventional adaptive backstepping method.In the system,the damping coefficient is measured inaccurately,and the reactance of transmission line also contains a few uncertainties.A nonlinear robust controller and parameter updating laws are obtained simultaneously.The system does not need to be linearized,and the closed-loop error system is guaranteed to be asymptotically stable.The design procedure and simulation results demonstrate the effectiveness of the proposed design.

A new adaptive backstepping method for nonlinear control of turbine main steam valve

A new approach for nonlinear adaptive control of turbine main steam valve is developed. In comparison with the existing controller based on ＂classical＂ adaptive backstepping, this method does not follow the classical certaintyequivalence principle in the design of adaptive control law. We introduce this approach, for the first time, to power systems and present a novel parameter estimator and dynamic feedback controller for a single machine infinite bus （SMIB） system with steam valve control. This system contains unknown parameters such as reactance of transmission lines. Besides preserving useful nonlinearities and the real-time estimation of uncertain parameters, the proposed approach possesses better performances with respect to the response of the system and the speed of adaptation. The simulation results demonstrate that the proposed approach is better than the design based on ＂classical＂ adaptive backstepping in terms of properties of stability and parameter estimation, and recovers the performance of the ＂full-information＂ controller. Hence, the proposed method provides an alternative for engineers in applications.

Adaptive H-infinity control of synchronous generators with steam valve via Hamiltonian function method

Based on Hamiltonian formulation, this paper proposes a design approach to nonlinear feedback excitation control of synchronous generators with steam valve control, disturbances and unknown parameters. It is shown that the dynamics of the synchronous generators can be expressed as a dissipative Hamiltonian system, based on which an adaptive H-infinity controller is then designed for the systems by using the structure properties of dissipative Hamiltonian systems. Simulations show that the controller obtained in this paper is very effective.

Nonlinear Steam Valve Adaptive Controller Design for the Power Systems

Considering generator rotor and valve by external disturbances for turbine regulating system, the nonlinear large disturbance attenuation controller and parameter updating law of turbine speed governor system are designed using backstepping method. The controller not only considers transmission line parameter uncer-tainty, and has attenuated the influences of large external disturbances on system output. The nonlinear con-troller does not have the sensitivity to the influences of external disturbances, but also has strong robustness for system parameters variation, which is because of the transmission line uncertainty being considered in internal disturbances. The simulation results show that the control effect of the large disturbance attenuation controller more advantages by comparing with the control performance of conventional nonlinear robust controller.

An experimental study on flowrate and stability for 600MW supercritical steam-turbine control valve

An experimental study on flowrate and stability of a type of control valve of 600MW supercritical steam-turbine was presented by measuring instruments of static, dynamic pressure and vibration in self-designed test rig. The investigation shows that flow coefficient is 30% up more than that of the control valve of GX-1 type used widely in domestic power plants now, as small-medium lifts. If the relative lift (h/D) is less than 20%, the valve can always work steadily in all the pressure ratios. When the h/D is between 20% to 24%, big vibration of valve stem occurs if the pressure ratio is between 0.7 to 0.8. When h/D is more than 25%, relatively great vibration happens in a wide range of pressure ratios of 0.4 to 0.85.

Study on Valve Management of DEH for Steam Turbine

Valve management is one of the major functions of DEH for steam turbine. It has an important practical significance for the security and economy of the steam turbine. This paper starts from the valve configuration figure of the domestic-type 300 MW steam turbine, and then makes a simple comparison between the two types of valve governing modes. In order to realize the valve control, the structure of control system has been established, in which the roles of the mathematical functions are discussed. On the basis of the experiment of valve flow characteristic, this article carries out a quantitative study on the functions of the valve management and the parameter tuning method. Through a serious corrections, the sequence valve flow characteristic curve is obtained, which can provide significant guidance on the research of valve management of the similar steam turbines.

Nonlinear variable structure excitation and steam valving controllers for power system stability

A set of novel nonlinear variable structure excitation and steam-valving controllers are proposed in this paper. On the basis of the classical dynamic equations of a generator, excitation control and steam valving control are simultaneously considered. Design of these controllers combines the differential geometry theory with the variable structure controlling theory. The mathematical model in the form of ＂an affine nonlinear system＂ is set up for the control design of a large-scale power plant. The dynamic performance of the nonlinear variable structure controllers proposed for a single machine connected to an infinite bus power system is simulated. Simulation results show that the nonlinear variable structure excitation and steam-valving controllers give satisfactory dynamic performance and good robustness.

A family of robust adaptive excitation controllers for synchronous generators with steam valve via Hamiltonian function method

Using the Hamiltonian function method, this paper proposes a family of robust adaptive excitation con- trollers for synchronous generators with steam valve control. First, a parameterization method of robust adaptive controllers is investigated for dissipative Hamiltonian systems. This method avoids solving Hamilton-Jacobi-Issacs inequalities. The parameters in the family of controllers thus obtained are determined by a locally positive semidefinite function, which has only 2n independent variables, twice as many as the one used to characterize the state feedback. Then, with the parame- terization method and the structural properties of dissipative Hamiltonian systems, a family of robust adaptive excitation controllers is designed for synchronous generators with steam valve control, disturbances and unknown parameters. Simu- lations illustrate the effectiveness and feasibility of the excitation control strategy proposed in the paper.

Primary Frequency Control Ability Evaluation of Valve Opening in Thermal Power Units Based on Artificial Neural Network

With the development of new energy,the primary frequency control(PFC)is becoming more and more important and complicated.To improve the reliability of the PFC,an evaluation method of primary frequency control ability(PFCA)was proposed.First,based on the coupling model of the coordinated control system(CCS)and digital electro-hydraulic control system(DEH),principle and control mode of the PFC were introduced in detail.The simulation results showed that the PFC of the CCS and DEH was the most effective control mode.Then,the analysis of the CCS model and variable condition revealed the internal relationship among main steam pressure,valve opening and power.In term of this,the radial basis function(RBF)neural network was established to estimate the PFCA.Because the simulation curves fit well with the actual curves,the accuracy of the coupling model was verified.On this basis,simulation data was produced by coupling model to verify the proposed evaluation method.The low predication error of main steam pressure,power and the PFCA indicated that the method was effective.In addition,the actual data obtained from historical operation data were used to estimate the PFCA accurately,which was the strongest evidence for this method.

核电主蒸汽阀站中电磁先导阀的动态响应仿真研究

针对核电主蒸汽阀站中关键部件之一——大气释放阀前置隔离阀在实际工况中常出现响应超时的问题,采用数值仿真软件Fluent中的动网格以及用户自定义函数技术,对控制其启闭过程的电磁先导阀动态响应过程进行了研究。首先,研究了电磁先导阀中先导结构的动态响应过程以及阀杆的受力情况;然后,研究了电磁先导阀中主阀的动态响应过程以及主阀泄压时阀内的压力和速度分布情况;最后,综合两个动态过程,分析了电磁先导阀整阀的运动时间。研究结果表明,电磁先导阀的运动时间为8.5 ms,其中先导结构的运动时间占比较小,85%的时间集中在电磁先导阀主阀动作过程。该研究结果可对前置隔离阀响应时间的优化提供参考。

汽轮机蒸汽管道与阀门及汽缸外缸外表面传热系数的计算模型和计算方法

构建了汽轮机蒸汽管道、主汽调节阀与汽缸外缸的外表面传热系数计算模型与计算方法。给出了汽轮机蒸汽管道、主汽调节阀、高压外缸、中压外缸与低压外缸的内表面传热系数以及保温结构外表面与低压外缸外表面的复合传热系数计算公式。建立了汽轮机蒸汽管道、高压外缸与中压外缸的金属内层壁与保温结构外层壁的双层圆筒壁、主汽调节阀金属内层壁与保温结构外层壁的双层球壁以及低压外缸单层圆筒壁的传热过程计算模型。考虑到金属内层壁内表面温度与外表面温度和保温结构外层壁外表面温度均为待定温度,采用迭代法确定这些汽轮机部件的表面温度、传热过程的传热系数与热流密度。完成了汽轮机蒸汽管道、主汽调节阀、高压外缸、中压外缸与低压外缸的外表面传热系数计算分析的应用实例,得出了这些汽轮机部件传热过程金属内层壁外表面的传热系数、热流密度与等效表面传热系数的计算结果,为这些汽轮机部件温度场与应力场的有限元数值计算提供了传热边界条件。

350 MW汽轮机高压调节阀阀位不跟踪指令问题的分析及处理

针对某350 MW汽轮机高压调节阀阀位不跟踪指令问题,通过分析阀门工作原理和阀芯组件受力情况,判断原因为阀碟与阀套氧化皮沉积、配合间隙减小,利用小修机会解体阀门验证了判断并一次性解决了问题,对同类型机组高压调节阀卡涩、关闭问题分析处理具有一定借鉴意义。

某水下打桩锤主控阀缓冲装置建模与仿真

为研究某水下打桩锤缓冲装置的结构对主控阀缓冲性能的影响,介绍缓冲装置的结构组成和缓冲原理,考虑液压油泄漏导致主控阀腔内压力和温度的变化,结合热力学和流体动力学理论建立缓冲装置的动态数学模型,基于MATLAB/Simulink软件搭建仿真模型并进行仿真分析,研究液压系统回油背压、缓冲腔直径、泄漏缝隙高度和长度等参数对缓冲性能的影响规律。结果表明:打桩锤主控阀缓冲装置的泄漏缝隙高度、泄漏缝隙长度和缓冲腔直径对缓冲性能的影响显著,液压系统的回油背压影响相对较小。研究结果为主控阀缓冲装置的设计和结构参数的优化提供理论依据。

核电主给水调节阀改进及仿真研究

在核电站中,主给水调节阀起着至关重要的作用,其性能的优劣直接影响到核电站的安全和稳定运行。本文针对某核电厂主给水调节阀存在的问题,提出了一种改进方案,并利用仿真技术对其进行了性能预测。结果表明,改进后的调节阀能够有效提高核电站的运行效率和安全性。

汽轮机主汽门异常关闭的原因排查及处理

调节保安系统是汽轮机的重要保护系统,其正常运行影响整个电厂的安全生产。某电厂汽轮机组在试运高压油泵过程时主汽门异常关闭,通过分析汽轮机危急遮断器的结构、工作原理及故障现象,对故障的原因进行逐一排查,最终得出了主汽门异常关闭的原因是附加保安油节流孔法兰缺少垫片,试运高压油泵过程中,附加保安油压扰动,危急遮断器滑阀下移,造成安全油泄放,导致主汽门关闭。通过重新安装垫片,缺陷得以消除。该异常现象可为其他同类型机组提供借鉴。

主蒸汽隔离阀驱动装置快关时间预测模型研究

主蒸汽隔离阀是保障核电站安全运行的关键设备,其快关时间是用于衡量主蒸汽隔离阀驱动装置最重要的动作性能指标之一。为了实现对主蒸汽隔离阀快关时间的快捷计算,在驱动装置系统仿真的基础上引入回归分析技术,提出了一种快关时间预测模型研究方法,为国产化研发提供参考。基于主蒸汽隔离阀驱动装置的系统仿真结果建立了单/双通道快关时间的预测模型,并采用测试数据对预测模型的可靠性和准确性进行了验证,结果表明提出的预测模型可以实现单/双通道快关时间的准确预测,其中,单通道快关时间预测误差不大于5.86%,平均预测误差为2.82%;双通道快关时间预测误差不大于5.80%,平均预测误差为2.77%。

CO_(2)压缩机控制系统节能优化对策

河南心连心公司7台离心式压缩机机组在运行过程中长期存在防喘阀无法全部关闭的现象,导致蒸汽通过回流或放空方式做无用功,为此选取公司江西基地CO_(2)离心压缩机机组进行优化。介绍了防喘振控制系统的优化思路、原理及过程。改造后,在条件允许的情况下,防喘阀在防喘振控制系统的作用下,可关至控制的最小开度,即运行点至防喘振调节线位置骑线运行;蒸汽使用量在额定工况下比原同等工况下降低2 t/h,每年可节约费用320万元左右。

300MW机组高压主汽门阀杆失效分析

高压主汽门是电站机组的关键部件之一,对机组安全启停和运行起着重要作用,长期承受高温高压工况下的复杂载荷。主汽门阀杆断裂是较为严重的一类故障,会造成巨大的经济损失。某电厂高压主汽门阀杆在机组运行过程中发生断裂,采用宏观检查、化学成分分析、金相组织观察、断口分析和力学性能测试等方法,对断裂原因进行了分析。结果显示,阀杆长期服役后材质劣化明显,力学性能严重下降,同时阀杆组织存在带状偏析,渗氮层和过渡层之间存在微裂纹。加工结构亦导致严重的应力集中,机组频繁启停导致阀杆疲劳损伤,这些因素共同导致阀杆断裂失效。

600 MW空冷机组汽轮机变负荷时#1轴瓦振大原因分析及措施探讨

汽轮机旋转设备的振动是反映设备自身安全的一个重要指标,振动异常问题是造成设备和结构失效及恶性破坏的直接原因。超限的振动一般预示着设备可能存在某种故障。针对600 MW空冷机组汽轮机增减负荷时#1轴瓦振动大的问题,结合机组实际运行需求,探索出了一种当机组存在轴瓦振动大问题时的汽轮机运行控制措施和停机检修措施,既实现了机组运行中的振动控制,也通过检修从根本上解决了汽轮机#1轴瓦振动大的问题,为同类型机组提供了一定的借鉴意义。

核电机组主蒸汽安全阀阀瓣密封面堆焊层开裂原因分析及预防措施

某核电厂大修期间对VVP116VV安全阀进行解体检查,发现阀瓣密封表面堆焊层存在20多条裂纹缺陷。通过宏观检查、化学成分分析、金相检验、硬度测试、残余应力分析、扫描电镜断口分析及能谱分析等方法分析阀瓣密封面堆焊层开裂的原因。结果表明:阀瓣密封面堆焊层的Fe含量明显偏高,表明稀释率过大,这与堆焊工艺控制不当(焊接热输入过大、热处理控制不当)有关。焊接热输入过大引起堆焊层残余应力偏高是开裂的主要原因;层间温度控制不当及焊后热处理不充分可能是促成堆焊层开裂的因素。并根据开裂的原因分析结果给出了处理建议,可以为其他机组的同类问题提供参考。