Development of a Full Parameterized FE-modeling Tool for Efficient Vibration Investigations on End Windings of Turbo- and Hydro-Generators

End windings of generators are excited to vibrations due to electromagnetic forces which can cause severe damage and noise. To avoid this, it is important to predict the natural frequencies and modes of the end windings with finite elements. Due to the complex structure and unknown boundary conditions, the conventionally calculation of stator end windings has been very difficult and time consuming up to now. This paper describes the development of a full parameterized modeling tool, which allows a quick calculation of natural frequencies during the design phase of the generator. To keep the computing time low, it is important to find a way to get exact calculation results without detailed modeling of all pans. Additionally, special attention was paid to the active part, which has been replaced by spring-damper elements, and the determination of their stiffness via experimental modal analysis combined with finite element calculations.

ZERO MODE NATURAL FREQUENCY AND NONLINEAR VIBRATION OF COUPLED LATERAL AND TORSION OF A LARGE TURBINE GENERATOR

Zero mode natural frequency (ZMNF) is found during experiments. The ZMNF andvibrations resulted by it are studied. First, calculating method of the ZMNF excited byelectromagnetic in vibrational system of coupled mechanics and electrics are given from the view ofmagnetic energy. Laws that the ZMNF varies with active power and exciting current are obtained andare verified by experiments. Then, coupled lateral and torsional vibration of rotor shaft system isstudied by considering rest eccentricity, rotating eccentricity and swing eccentricity. UsingLargrange-Maxwell equation when three phases are asymmetric derives differential equation of thecoupled vibration. With energy method of nonlinear vibration, amplitude-frequency characteristics ofresonance are studied when rotating speed of rotor equals to ZMNF. The results show that ZMNF willoccur in turbine generators by the action of electromagnetic. Because ZMNF varies withelectromagnetic parameters, resonance can occur when exciting frequency of the rotor speed is fixedwhereas exciting current change. And also find that a generator is in the state of large amplitudein rated exciting current.

Transient Model for Shafting Vibration of Hydro Turbine Generating Sets

The shafting vibration is closely related to the rotational angular speed.The angular speed of hydro turbine generating sets(HTGS)is rapidly change in fault transient,it maybe reduce the shafting damage.By means of energy analysis,the differential equation of shafting vibration for the HTGS is derived,in which include the equation of generator rotor and hydro turbine runner,it can be applied to transient analysis.Shafting model is transformed into first order differential equation groups,and is combined with the motion equation of HTGS to build integrated model.Various additional forces of shafting are taken as input inspire in proposed model,the generality of model is good.At last,the shafting vibration in emergency stop transient is simulated.

An Integrated Wind and Hydro Power System Using Switched Reluctance Generator

This research work seeks to make renewable energy more reliable, cost effective, and accessible by exploring a different energy combination system to that currently applied to wind and hydro power. Instead of the usual electrical combination of wind and hydro generators, this work involved combining a water and wind turbine mechanically, before driving an electrical generator. This new combination system was modeled and optimized in MATLAB, using a direct combination system commonly found in multi-engine helicopters. The system was found to operate satisfactorily, however it is mechanically more complex than current electrical combining systems. Research was undertaken regarding wind and water resource availability, and the turbines were chosen with these taken into consideration. Various combination systems were explored, including torque and speed split mechanical combinations, conventional electrical combination, and using a modified switched reluctance generator as a method of electro-mechanical combination. The generator selected for this work is a three phase 12/8 Switched Reluctance (SR) machine. A detailed winding polarity having four poles per phase and their effect on the performance of the machine is

燃料串/并联的航空SOFC-GT混合系统性能对比分析

固体氧化物燃料电池-涡轮(SOFC-GT)混合系统作为电推进飞机的动力源时,会面临低温低压的大气环境以及对重量有严苛的要求,因此通过优化系统构型使得该混合系统满足航空应用是一种有效的解决方式。为此本文提出了燃料并联和串联的两种SOFC-GT混合系统构型,并从热力循环理论、系统热力学性能以及系统功重比等方面依次对其进行了对比分析。结果表明,并联系统的热力学性能要优于串联系统,对于系统发电效率、比功和功重比分别提高3.32%,113.14%和34.04%,CO_(2)排放率降低3.22%。随压比的提升串联系统的效率存在最优点,随燃烧室温度的提升并联系统的效率持续下降。在空燃比为4~6的变化范围内,串联系统的输出功率变化幅度更大,相对并联系统为116.29%~87.11%。除此之外,虽然SOFC-GT混合系统的功重比相对较低,但基于其优异的效率,在系统能量密度方面整体要优于锂电池,这有利于提升电推进飞机的性能。

Performance Investigation of a Simple Reaction Water Turbine for Power Generation from Low Head Micro Hydro Resources

Theoretical investigation has shown a simple reaction water turbine would perform better when it spins faster. And for the simple reaction turbine water turbine to spin faster under constant water head, its diameter should be smaller. This paper reports on a performance analysis based on the experimental data collected from different performance tests carried on two simple reaction water turbine prototypes. Two new designs of simple reaction water turbines and their manufacturing methods are reported. The two turbines under investigation have different rotor diameters Φ 0.243 m and Φ 0.122 m. In case of the simple reaction water turbine the water enters into the turbine axially and exits tangentially through nozzles located on the outer periphery of the turbine. Further this paper will discuss the performance characteristics of stationary turbine i.e. zero power produced and performance characteristics of turbine producing power. It was found that rotor diameter affects the maximum rotational speed of the simple reaction turbine for constant supply head. It was also found that faster the turbine spins its performance improves. The two turbines were tested between supply head range of 1 m to 4 m.

Characteristics of Mechanical and Electrical Power Transmission for Small-Scaled Wind Turbine

Small-scaled wind turbine is converted to mechanical power of windmill to electric power by generator. However almost all studies seems to have overlooked converting relation of mechanical & electric power. It the reason for was very difficult establishing wind turbine system. In this paper, it is define equation of converting relation of mechanical & electric power. And it is verified by experimental methods. Defined equation will be used in developing electric devices such as inverter and controller in wind turbines. In addition this method can be used in the fields that utilize the rotational power into electrical power through generator.

Analysis of Nigerian Electricity Generation Multi Year Tariff Order Pricing Model

The Multi Year Tariff Order (MYTO) is the Nigerian Electricity Regulatory Commission (NERC) pricing framework for determining the Nigerian Electricity Supply Industry (NESI) pricing model. One of the objectives of the NERC’s MYTO pricing model is to ensure regulated electricity end user tariff without compromising return on investment. Achieving this objective is imperative to attract investors in the growing Nigerian electricity market. However, NESI has hitherto been faced with challenges ranging from its inability to provide sufficient power to its customers to not being viable enough to provide return on capital invested. In this paper, sensitivity analysis of power plant operation and performance parameters on the cost of electricity (CoE) generation using MYTO (power generation) pricing model were evaluated. Thermodynamic modeling and simulation of an open cycle gas turbine (OCGT) was carried out to augment scarce data on power plant performance and operation in Nigeria. Sensitivity analysis was carried out using probabilistic method based on Monte Carlo simulation (MCS) implemented in commercial software (@ Risk®). The result highlighted sensitivity of the model input parameters to cost of electricity generation based on technical and financial assumptions of MYTO model. Seven most influential parameters affecting generation cost were identified. These parameters and their correlation coefficients are given as: 1) foreign exchange rate, 0.76;2) cost of fuel, 0.51;3) thermal efficiency, -0.23;4) variable operation and maintenance cost, 0.22;5) fixed operating and maintenance cost, -0.03;6) capacity factor, -0.02;and 7) average capacity degradation, 0.01. Based on the gas turbine engine and input parameter distributions statistics for this study, the generation cost lies between 9.84 to 15.45 N/kWh and the probabilities of CoE within these values were established.

Determination of the Orthotropic Material Behavior of Stator Bars and of the Material Characteristics of the Space Brackets

The end windings of generators are excited to vibrations due to electromagnetic forces which can cause severe damage （especially in case of resonance） and noise. To avoid this, it is important to predict the natural frequencies and modes of the end windings with finite elements during the design process. Hence, a material model of the complete stator bar is necessary. This paper shows the development of such a material model. The composite structure of a stator bar is quite complex and makes it impossible to provide a quick calculation of the eigenvalues. That is the reason for using a suitable, homogeneously, geometry based solid model. Special attention was paid to the experimental determination of the material characteristics of the orthotropic composite space brackets. The numerical results have been evaluated against measurements. Eigenvalues, Young＇s modulus, and shear modulus have been experimentally investigated.

Wind Turbine Noise Reduction through Blade Retrofitting

This paper outlines a plan for the effective reduction of the audible sound level produced by aerodynamic noise from the power-generating turbine blades. The contribution of aerodynamic noise can be divided into two categories: inflow turbulence and airfoil self-noise. The base model and retrofit blade designs were modeled in SolidWorks. Subsequently, noise prediction simulations were conducted and compared to the base blade model to determine which modification provided the greatest benefit using SolidWorks Flow Simulation. The result of this project is a series of blade retrofit recommendations that produce a more acoustically efficient design and reduce noise complaints while enabling turbines to be placed in locations that require quieter operations.

Distributed Model Predictive Load Frequency Control of Multi-area Power System with DFIGs

Reliable load frequency control LFC is crucial to the operation and design of modern electric power systems. Considering the LFC problem of a four-Area interconnected power system with wind turbines, this paper presents a distributed model predictive control DMPC based on coordination scheme. The proposed algorithm solves a series of local optimization problems to minimize a performance objective for each control area. The generation rate constraints GRCs, load disturbance changes, and the wind speed constraints are considered. Furthermore, the DMPC algorithm may reduce the impact of the randomness and intermittence of wind turbine effectively. A performance comparison between the proposed controller with and without the participation of the wind turbines is carried out. Analysis and simulation results show possible improvements on closed-loop performance, and computational burden with the physical constraints. © 2014 Chinese Association of Automation.

Wind Turbines as Additional Power Supply

Recently, mankind’s need for more amount of energy has been increasing day by day, though there is a trend to reduce the usage of the traditional energy source to an energy carrier (or fuel) that results in emitting harmful gases to the envi-ronment that is separated in the air and water. Researchers have conducted re-searches to increase projects that will generate clean and renewable energy. Us-age of renewable energy via mankind is in continuous progress such as solar en-ergy, bioenergy, ocean energy and wind energy. Wind energy waste while the car moved was used to produce electric energy. In this paper, the usage of unused wind energy in vehicles was developed so that additional power for vehicles was enable via converting wind power into electric one. The wind turbine was assem-bled from a fan and transducer. Indoor test showed generation of different elec-tric voltages when varying the ambient temperature. The main experiment was carried out so that the wind turbine was installed above the car;values of volt-ages in various speeds of the car were recorded. When two fans were used with different specifications, the consequence was a direct proportionality that changes the happened between voltages and car’s speeds. A comparison between the two fans showed that: the fan with big blade dimensions was the best one to generate voltages. Finally, the high voltages were generated in low temperatures. These results reveal that we can avail from wind energy to supply vehicles with electricity as long as vehicles move along the way.

木材用于水伏发电的研究进展

化石能源的过度使用带来能源枯竭与环境恶化问题,绿色可持续成为发展的首要目标。水能作为目前较为优质的清洁能源,其中一部分潜在的能量有待转化利用。近年来,水伏发电受到国内外学者的广泛关注,被认为是一种新兴的深度挖掘水能资源的手段,研究者们取得了一系列关于功能材料与水滴、水波、水蒸发与湿气等相互作用输出电能的研究成果。开发生物质基水伏发电材料有助于推动可再生能源的充分利用。木材是一种储量充足、可再生、易加工的材料,同时具有独特的多级孔道结构,内部富含极性基团,有良好的机械强度,因此木材在水伏发电领域具有一定应用前景。笔者总结了水伏发电技术的研究进展,阐述了水伏发电的理论基础,基于水伏效应的能量转换方式及其器件材料的选择,介绍了木材用作水伏发电器件材料的研究成果,归纳了研究者为提高水伏发电器件的输出功率,对木材进行表面修饰、孔道调控、材料负载、碳化处理的功能化改性方法,并对其面临的挑战与应用前景进行展望。

双馈虚拟同步机快速励磁控制和功角补偿策略

针对以激磁电势为目标控制电压的双馈虚拟同步发电机策略下运行功角大而带来的功率耦合问题,提出采用快速励磁控制消除功角扰动对无功控制的影响,采用功角补偿消除激磁电势扰动对功角有功控制的影响的功率解耦方案。在分析双馈电机数学模型及双馈虚拟同步机整体控制策略的基础上,构建计及无功控制环节的双馈虚拟同步机小信号模型。通过分析无功环节PI控制器参数对功角稳定性的影响,设计快速励磁控制策略。通过分析无功扰动与功角变化的关系,确定功角补偿传递函数。设定风速扰动、电网频率扰动和电网电压扰动3种不同工况进行验证。结果表明:所提控制策略可有效避免双馈虚拟同步机大功角运行时有功功率控制和无功功率控制间的相互影响,实现功率解耦。

水电厂机组可靠性分析与实际应用

水电厂可靠性指标是衡量机组运行、检修及故障停运情况的重要指标。文章基于高坝洲水力发电厂2012-2021年机组运行的可靠性指标统计数据表明,近十年设备维护得当,机组运行稳定可靠,为电网安全稳定运行提供了有力保障。同时从管理方法上分享了提高机组可靠性有效途径,可供同行借鉴。

消防水枪绿色自馈能电照明系统的设计与实现

针对传统消防水枪黑暗环境下照明效果不理想的问题,提出了消防水枪绿色自馈能电照明系统的设计方案。通过重新设计消防水枪涡轮发电机的结构及发电机的整流稳压与保护电路,优化消防水枪储能技术设计,实现消防水枪的自馈能技术,显著提高了能源利用效率和照明效果。与传统消防水枪相比,该系统具有显著的优势和潜力,为消防设备的改进和能源利用提供了新的解决方案。

水光储互补特微型发电系统设计与评估

针对美丽乡村建设不断增长的绿色发展需求,提出了一种采用虹吸式水轮机和光伏板作为发电装置,配合蓄电池储能的水光储互补特微型发电照明系统方案。虹吸式水轮机使用稳态数值模拟计算出力及效率,结合水位数据计算发电量,光伏板使用面积法结合太阳辐射数据估算月发电量,并计算了提供给夜间照明和电网的电量。分析了系统的建设成本、经济效益和减排效益,结果表明本系统拥有切实可行的推广前景和减排效益。

高海拔地区18 kV水轮发电机定子绕组端部防晕技术研究

为满足海拔高度为2 500 m的某大型水电站18 kV水轮发电机的防晕要求,本文从理论方面分析了目标海拔高度下的空气击穿场强及影响因素,并通过建立定子绕组端部三维仿真模型评估了端部电场特性,分析了间隙距离与绑扎结构对端部斜边电场的影响,确定了定子绕组端部斜边最小间隙距离控制在15 mm的方案。最后,在构建的大型高海拔环境模拟试验室完成了18 kV水轮发电机定子线圈和绕组的防晕性能进行测试验证。结果表明:该18 kV水轮发电机的防晕性能良好,满足在2 500 m海拔高度下的防晕要求。

水轮发电机组筒形阀检修工艺优化及应用

受到检修操作空间、结构布置等限制,大型水轮发电机组筒形阀检修难度增加。针对筒形阀接力器提升杆更换问题,从筒形阀接力器提升杆更换检修流程、下端盖水平度调整、提升杆垂直度调整等环节着手,优化检修工艺。该套检修工艺应用于溪洛渡水电厂某台机组筒形阀检修,取得了满意效果。

立式水轮发电机定子内膛及端部清扫检查装置的研究

立式水轮发电机在B级检修期间,需拔出一对磁极后,对定子绕组端部、定子通风槽等进行人工清扫检查,常规方式采用带电清洗剂进行人工冲洗,并对定子槽口、定子内膛等进行重点检查,存在工作效率低、清洗剂影响作业人员呼吸道健康、空间狭小导致检查不充分等问题,为此研制了自动清扫装置。该装置的投入,减轻了作业人员劳动强度,缩短了清洗检查时间,提高了检修效率。