Multi-model Predictive Control of Ultra-supercritical Coal-fired Power Unit

The control of ultra-supercritical(USC) power unit is a difficult issue for its characteristic of the nonlinearity, large dead time and coupling of the unit. In this paper, model predictive control(MPC) based on multi-model and double layered optimization is introduced for coordinated control of USC unit. The linear programming(LP) combined with quadratic programming(QP) is used in steady optimization for computation of the ideal value of dynamic optimization. Three inputs(i.e. valve opening, coal flow and feedwater flow) are employed to control three outputs(i.e. load, main steam temperature and main steam pressure). The step response models for the dynamic matrix control(DMC) are constructed using the three inputs and the three outputs. Piecewise models are built at selected operation points. Double-layered multi-model predictive controller is implemented in simulation with satisfactory performance.

Exergy Analysis and Thermal Optimization of a Double-Turbine Regeneration System in a Ultra-Supercritical Double-Reheat Unit

Improving the primary steam parameters is one of the most direct ways to improve the cycle efficiency of a powergeneration system. In the present study, the typical problem connected to the excessively high superheat degree ofextraction steam in an ultra-supercritical (USC) double-reheat unit is considered. Using a 1000 MW power plantas an example, two systems (case 1 and case 2) are proposed, both working in combination with a regenerativesteam turbine. The thermal performances of these two systems are compared with that of the original systemthrough a heat balance method and an exergy balance strategy. The results reveal that the two coupled systemscan significantly reduce the superheat degree of extraction steam, turbine heat rate, and coal consumption of theunit and improve the energy utilization efficiency. These results will provide useful theoretical guidance to futureinvestigators wishing to address the general problem relating to energy conservation and modelling of the coupledextraction steam regenerative system of USC double-reheat units.

Vibration of 1000-MW Ultra-Supercritical Turbine-Generator Unit with Simens Technology

The layout features of unit shafting and their effects on vibration, as well as evaluation criteria, were introduced for a 1000-MW ultra-supercritical turbine-generator unit with Simens technology. Based on vibration diagnosis and treatment for more than 10 units, some typical vibration faults were summarized, such as the vibration fluctuation of the high pressure (HP) rotor, abnormal vibration increases of the No.3 bearing pedestal and large vibration of the exciter rotor during its critical speed range. The vibration characteristics and the causes of faults and countermeasures were analyzed. Three applications for further illustration were given. The vibration fault identification method, control measures, and applications can provide a reference for vibration diagnoses and treatment of same type units.

Model Identification Based on Subspace Model Identification of Main Steam Temperature in Ultra-Supercritical Coal-Fired Power Unit

Ultra-supercritical(USC) unit is more and more popular in coal-fired power industry.In this paper,closed-loop identification based on subspace model identification(SMI) is introduced for superheated steam temperature system of USC unit.Closed-loop SMI is applied to building step response model of the unit directly.The parameters selection method is proposed to deal with the parameter sensitivity and improve the reliability of the model.Finally,the model is used in model identification of real USC unit.

Development Features of Supercritical (Ultra-Supercritical) Technology in the World and Experiences We Can Learn

The development and technical characteristics in different stages of supercritical (ultra-Supercritical) technology abroad are introduced in this paper. At the same time, according to the development trend of supercritical (ultra-supercritical) technology, the corresponding revelations are given in this paper. That is: It is an inevitable choice to develop supercritical (ultra-supercritical) technology if we want to improve the thermal efficiency and heat efficiency.

Research on the Prediction of Load Regulation Capacity for Supercritical Thermal Power Unit

Both the modeling and the load regulation capacity prediction of a supercritical power plant are investigated in this paper. Firstly, an indirect identification method based on subspace identification method is proposed. The obtained identification model is verified by the actual operation data and the dynamic characteristics of the system are well reproduced. Secondly, the model is used to predict the load regulation capacity of thermal power unit. The power, main steam pressure, main steam temperature and other parameters are simulated respectively when the unit load is going up and down. Under the actual constraints, the load regulation capacity of thermal power unit can be predicted quickly.

Application of Homemade DCS in Integrated BOP Control of 600-MW Supercritical Unit

The PLC and upper computer are used in BOP control system of traditional thermal power plant to monitor the in-situ equipment. It is complicated and wastes labor and resources. It is difficult to maintain and manage them. Beijing GuoDian ZhiShen Control Technology applied the homemade DCS (EDPF-NT System) to the integrated BOP control system of 600-MW supercritical power unit, which offers advantages in efficiency promotion, cost reduction and resource sharing. That also reflects the dominance of EDPF-NT System in performance, price, real-time DUP, network compatibility and communication. This article introduces the main characteristics, structure and configuration of EDPF-NT System, as well as the hierarchical operation, the multi-domain network structure and the private network router developed for Zhuanghe Power Plant.

Experimental Study on Performance of Supercritical CO_2 Heat Exchanger with Four Different Inner Tubes

The experiment was conducted to investigate the heat transfer performance of supercritical CO_2 in a casing heat exchanger by comparing their heat transfer,entropy production unit number,non-dimensional entropy production rate and field synergy factor.The results show that both heat transfer and entropy production unit number in four tubes decrease with water temperature increasing.Heat transfer and entropy production unit number in multiple tubes( i. e.,triple straight tube and double helix tube) is higher than their single counterparts; the non-dimensional entropy production rate increases with water temperature. Non-dimensional entropy production rate of triple straight tube and double helix tube is far below the single tube. Field synergy factor of double helix tube is much higher than that of the triple straight tube under the same condition. Further experiment was carried out in double helix tube,under various CO_2 pressure and inlet water temperature,the results are analyzed and reported in this paper.

Energy-Saving Optimization Study on 700℃ Double Reheat Advanced Ultra-Supercritical Coal-Fired Power Generation System

700°C double reheat advanced ultra-supercritical power generation technology is one of the most important development directions for the efficient and clean utilization of coal.To solve the great exergy loss problem caused by the high superheat degrees of regenerative steam extractions in 700°C double reheat advanced ultra-supercritical power generation system,two optimization systems are proposed in this paper.System 1 is integrated with the back pressure extraction steam turbine,and system 2 is simultaneously integrated with both the outside steam cooler and back pressure extraction steam turbine.The system performance models are built by the Ebsilon Professional software.The performances of optimized systems are analyzed by the unit consumption method.The off-design performances of optimization systems are analyzed.The results show that:the standard power generation coal consumption rates of optimization systems 1 and 2 are decreased by 1.88 g·(kW·h)^(–1),2.97 g·(kW·h)^(–1)compared with that of the 700°C reference system;the average superheat degrees of regenerative steam extractions of optimized systems 1 and 2 are decreased by 122.2°C,140.7°C(100%turbine heat acceptance condition),respectively.The comparison results also show that the performance of the optimized system 2 is better than those of the optimized system 1 and the 700°C reference system.The power generation standard coal consumption rate and the power generation efficiency of the optimized system 2 are about 232.08 g·(kW·h)^(–1)and 52.96%(100%turbine heat acceptance condition),respectively.

不同参数高效超超临界机组经济性分析及建议

本文根据目前大量已投运二次再热机组运行经验,结合某660MW项目高效一次再热和二次再热不同的高效超超临界参数,结合对应的汽机热平衡图参数,通过对THA、80%THA、60%THA三个运行负荷进行了相关的机组经济性参数的计算和对比,通过分析提出了在选择一次再热或二次再热参数上的一些建议和结论。

基于SDAE的超临界机组协调系统特性建模

为采用预测控制方法改善超临界机组的协调控制品质,采用堆叠降噪自编码器(SDAE)建立了单元机组协调系统特性的数学模型。首先,对600MW火电机组的变工况运行数据进行归一化处理,并运用预处理后的数据完成模型的离线训练。将模型并入仿真机进行单一输入变量阶跃扰动和大幅变负荷实验来验证其动态性能。实验结果表明,上述模型能够很好地描述燃料量、汽轮机调门开度、给水量与主蒸汽压力、负荷间的复杂非线性关系,泛化能力强、精度高,可以满足超临界机组智能控制器的设计要求。

P92钢接头Ⅳ型开裂蠕变孔洞临界值的分析及应用

【目的】分析P92管道接头热影响区发生Ⅳ型开裂的蠕变孔洞临界值的影响因素,得到蠕变孔洞临界值计算方法,为评估接头开裂风险提供依据。【方法】收集服役后发生Ⅳ型开裂的P92接头,在未开裂处取样进行610℃下不同应力条件的高温持久蠕变试验,然后使用光学显微镜、电子显微镜观察服役开裂接头和持久断裂接头热影响区的蠕变孔洞分布形貌,并借助图像分析软件测量蠕变孔洞的面积分数,同时使用硬度仪测试热影响区软化情况,最后综合测试结果分析细晶区软化程度和接头应力水平对蠕变孔洞临界值的影响,并拟合应力、显微硬度、孔洞临界值三者之间的函数关系。【结果】研究发现,P92钢接头细晶区相比于接头其它区域软化速度更快,但软化作用并非其发生Ⅳ型开裂的必要条件,当应力水平较高时,细晶区没有发生明显软化时就可以触发蠕变开裂;得到接头轴向应力水平、蠕变孔洞面积分数临界值和显微硬度的函数关系式。【结论】引起Ⅳ型开裂的蠕变孔洞面积分数临界值与相对应力水平(轴向应力与硬度的比值)有关,相对应力水平越高,蠕变孔洞临界值越小,接头安全性就越低;通过测量接头细晶热影响区的蠕变孔洞面积分数和显微硬度,可以估算开裂接头的轴向应力水平,也可以评估在役未开裂接头的Ⅳ型开裂风险。

燃用高硫煤锅炉空预器选型分析

为有效解决2×660MW燃用高硫煤超超临界机组空预器堵塞问题,研究了回转式空预器和管式空预器特性,分析了机组特点,提出了回转式空预器和管式空预器两级换热器串联方案,并探究了该方案对机组锅炉效率的影响。研究表明,相比于常规回转式空预器方案,采用回转式空预器和管式空预器两级换热器串联方案时,回转式空预器的出口排烟温度高于烟气酸露点,有效解决了机组空预器腐蚀堵塞问题,同时在保证设备安全下使锅炉效率提高1%。

基于Q学习的超超临界机组协调系统模型预测控制研究

超超临界机组具有多输入多输出、非线性严重、耦合强、时滞大的特点,其控制系统的设计要求是在保证系统稳定运行的同时,最大限度地提高机组的热效率和功率输出、快速准确地调节机组负荷、确保机组主蒸汽压力和温度在允许范围。通过调整系统模型以及阶段成本,进而获取最优策略。选取强化学习中的Q学习方法。将参数化模型预测控制作为Q学习中的一种新型函数逼近器,通过调整模型预测控制的参数来获取近似最优闭环控制策略以及最优的值函数。将该方法应用到1 GW超超临界锅炉汽轮机协调系统的控制中。在升负荷以及小范围升负荷变化情况下进行仿真。仿真结果表明,与传统模型预测控制方法对比,该方法可以在满足约束的情况下使系统输出值更加准确地到达设定值。

偏置量影响的超超临界汽轮机转子密封动力特性

超超临界汽轮机运行时不平衡的汽流冲击力会引发汽流激振,以某1000MW汽轮机超高压缸隔板迷宫密封为研究对象,采用改进的涡动方程控制转子实现多频涡动,分析了不同偏置量对密封动力特性的影响。结果表明:直接刚度k_(yy)随涡动频率的增加而增加,直接阻尼c_(yy)在30Hz以前先降低后不变。随着压比的增加,有效阻尼增大,转子的稳定性提高。各偏置量下直接刚度k_(yy)朝着正方向增大,c_(yy)随频率的增加先大幅度减小最后近似不变,偏置量引起的密封气动特性变化在高压区域较强。

超超临界机组再热热段疏水管弯头断裂失效分析

为了研究再热热段疏水管弯头断裂的原因,以某火力发电厂1000 MW超超临界机组B侧再热热段疏水管为研究对象,对弯头断裂处及附近位置进行了宏观形貌、金相组织、硬度以及力学性能进行了试验分析,疏水管材质为P92,规格为38.1mm×5mm,工作温度603℃,工作压力4.79 MPa。结果表明:一方面,疏水管温度存在反复变化情况,管壁的膨胀与收缩受到一定程度的约束从而产生热应力循环,疏水管弯头产生疲劳损伤,出现热疲劳裂纹;另一方面,弯头外壁存在凹坑,凹坑处易产生裂纹,同时,弯头位置硬度值超过标准上限,使得弯头抗形变能力降低,在排出凝结水过程中,机组负荷变化和排出凝结水的间歇性致使介质流速发生变化,弯头处振动明显,致使弯头处裂纹进一步发展直至出现断裂。

基于LSTM神经网络算法的超超临界机组负荷优化分配

目前研究的超超临界机组负荷优化分配方法成本较高,分配时间过长,导致节能效果不佳。为此,该文基于LSTM神经网络算法研究了一种新的超超临界机组负荷优化分配方法。利用LSTM中的记忆块、遗忘门、输入门、输出门和记忆单元,实现对递归神经网络的简单处理,建立目标函数,采用正平衡法和反平衡法计算电荷吸收效率,确定超超临界机组负荷优化分配数学模型。针对单元制机组模型和母管制机组模型在忘记阶段、选择记忆阶段与输出阶段进行优化,反复迭代,得到迭代最大次数后停止运行,输出优化结果。实验结果表明,与传统优化方法相比,所设计超超临界机组负荷优化分配方法可将成本降低50%以上,1000 MW内负荷分配时间低于10 min。

基于Pearson相关性的VAR模型煤电水煤比寻优应用

本文为解决350MW燃煤机组在煤质频繁变化情况下水煤比失衡的问题,使用向量自回归(VAR)模型在机组参数波动工况下进行水煤比寻优。通过使用Pearson相关系数分析机组运行参数,确定寻优模型的输入数据,计算VAR模型最优阶数,并建立VAR模型从多个参数的时间序列寻找对应工况下水煤比最优值,同时使用三种不同分析方法确保该最优值的准确性和安全性。实践证明,该方法能有效解决机组由于煤质频繁变化导致锅炉给水策略不适配引发的主蒸汽温度和主蒸汽压力偏差大等问题。

1000 MW超超临界机组精处理系统改造及智能化升级

某电厂2×1000 MW超超临界机组锅炉给水采用加氧处理(OT),利用西安热工研究院“火电厂高速混床运行性能诊断及优化专家系统”对精处理高速混床和再生系统进行诊断,发现运行末期泄漏离子、再生系统缺乏智能监控装置及再生酸碱用量大等问题。应用树脂输送图像智能识别及控制仪(IRIC)和双层多孔板布水装置改造后,树脂体外再生过程实现了智能控制,树脂输送终点识别准确率100%;高速混床平均周期制水量增幅108%,出水Na^(+)和Cl^(-)含量均优于《火力发电机组及蒸汽动力设备水汽质量》(GB/T 12145—2016)要求,经济效益和安全效益显著。