电力发电机组负序电流产生及过热保护实现研究

文章分析了电力发电机组负序电流产生的原因,针对负序电流的危害,提出过热保护的措施和方法,经过对135MW发电机组端口负序电流测定,能够精确地对保护值进行整定,提高发电机组运行的安全性。

电力发电机转子的检修技术与应用探析

当前,电力设备在人们日常生活以及工作中发挥重要作用,因此,也使电力设备检修作业重要性越发凸显。近年来,在日常生活以及生产作业中所需设备质量要求逐渐提高,在电力设备运行中,电力发电机转子作为其重要构成,对于发电机转子的检修技术要求逐渐提升。本研究主要阐述当前转子检修技术发展现状,进一步分析现有可应用技术和方法,同时,以感应加热法为例,分析该方法在电力发电机转子检修中的具体应用,以期能够提升发电机检修质量,进一步确保发电机能够实现安全运行。

电力系统发电机组的检修策略探索

随着经济的发展,用电量的不断上升,电网事业也在突飞猛进地发展,怎样确保电力系统的安全稳定运行,成为电力系统变电检修的主要问题。由于电力系统比较复杂,需要维护的设备较多,容易出现故障和发生异常,这就需要加强对电力系统的检测,提高电力系统的防预能力,减少事故发生的概率。本文就针对电力系统发电机关联的机组检修进行系统的分析。

电厂发电机常见故障原因分析及预防

随着我国经济的不断发展,我国各个领域的建设都在快速地进行中,然而这些建设项目离不开电力的支持,现在我国的用电总量是很大的。电力也是一种重要的能源,必须对其高效率地使用才能达到长远性发展的目的,另外,对于电力的管理工作也是很多的,为了保证电力输出率与工作效率,我们针对发电机故障的成因和维修展开讨论。

基于混合遗传算法的火力发电厂AGC控制方法

在自动发电控制(AGC)过程中,对发电机参数的设置难以达到最优,导致控制效果与理想状态存在一定偏差。为此,文章提出基于混合遗传算法的火力发电厂AGC控制方法。结合火力发电厂发电机运行机制与整体输出之间的关系,构建了发电机-电力系统模型,量化了1%频率变化所带来的负荷变化程度。在实施AGC控制的过程中,引入了混合遗传算法,分别设置了单步学习和多步学习动作,当二者的学习结果差值恒定后,将对应的参数值作为发电机的设置结果,以此实现火力发电厂AGC控制。根据测试结果,设计控制方法下发电厂的调节容量上限和下限均随着调节容量效能系数的改变发生线性变化,与理想控制效果一致。

Study on Electromagnetic Force and Vibration of Turbogenerator End Windings under Impact Load(Ⅰ): Analysis of Electromagnetic Force of End Windings under Impact Load

In this paper, the boundary value problem (BVP) of 3 D transient eddy current field in the end region in the case that the generator is affected by impact load is specified. Besides, ways to implement discrete methods in both time domain and space domain during the solution of the problem are investigated. The Crank Nicolson scheme is utilized to attain the iterative format of time differential, after taking factors that can ensure both computation precision and stability into consideration. In this paper, the magnetic distribution in the end region of a turbogenerator in the case that the generator is affected by impact load is specified. As a result, it provides foundation for further study of electromagnetic force and electromagnetic vibration in the end region of the turbogenerator.

Study on Electromagnetic Force and Vibration of Turbogenerator End Windings under Impact Load(Ⅱ): Analysis of Vibration of End Windings under Impact Load

On the basis of the study of transient eddy current field in the end region of turbogenerator and electromagnetic force of end region winding, this paper analyzes the electromagnetic vibration of the turbogenerator roundly. A 320 MW turbogenerator is taken as an example to specify the electromagnetic force of end region winding and therefore the vibration in the case that the generator is affected by impact load. Some conclusions are drawn on the basis of the specification. Vibration of windings under imaginary faults is simulated, so that the vibration law of the end winding of turbogenerator can be studied further. On the basis of this, the countermeasure against winding vibration can be advanced.

Retrospect and Prospect of Excitation Systems of Large Size Turbogenerators

This paper briefs the developmental course, manufacturing and applications, as well as future prospect of excitation systems of large size turbogenerators in China, emphatically expounds the advantages of seif-excitation systems with potential source reetifiers and matters needing to be noted during dissemination and application of them.

Adaptive rotor current control for wind-turbine driven DFIG using resonant controllers in a rotor rotating reference frame

This paper proposes an adaptive rotor current controller for doubly-fed induction generator (DFIG), which consists of a proportional (P) controller and two harmonic resonant (R) controllers implemented in the rotor rotating reference frame. The two resonant controllers are tuned at slip frequencies ωslip+ and ωslip-, respectively. As a result, the positive- and negative-sequence components of the rotor current are fully regulated by the PR controller without involving the positive- and negative-sequence decomposition, which in effect improves the fault ride-through (FRT) capability of the DFIG-based wind power generation system during the period of large transient grid voltage unbalance. Correctness of the theoretical analysis and feasibility of the proposed unbalanced control scheme are validated by simulation on a 1.5-MW DFIG wind power generation system.

Special report on relationship between wind farms and power grids

The installed capacity of a large scale wind power plant will be up to a number of hundreds MW, and the wind power is transmitted to load centers through long distance transmission lines with 220 kV, 500 kV, or 750 kV. Therefore, it is necessary not only considering the power transmission line between a wind power plant and the first connection node of the power network, but also the power network among the group of those wind power plants in a wind power base, the integration network from the base to the existed grids, as well as the distribution and consumption of the wind power generation by loads. Meanwhile, the impact of wind power stochastic fluctuation on power systems must be studied. In recent years, wind power prediction technology has been studied by the utilities and wind power plants. As a matter of fact, some European countries have used this prediction technology as a tool in national power dispatch centers and wind power companies.

浅谈高技术海工船舶电站管理系统

船舶电站管理系统是船舶动力系统的核心部分,也是船舶自动化系统的重要组成部分。武船承建的PX121H PSV海洋工程平台供应船为典型的海洋工程全电力推进船舶,其电站管理系统(Power Management System,PMS)在现代高技术船舶电站管理系统中具有代表性。本文介绍了PX121H PSV电站管理系统的系统配置结构和功能,对船舶设计、调试人员起一定学习、参考作用。

Impact of Wind Integration on Transient Voltage Stability in Regional Grid

With the increasing development of wind power,the scale of wind farms and unit capacity of wind turbines are getting larger and larger,and the impact of wind integration on power systems cannot be ignored.However,in most cases,the areas with a plenty of wind resources do not have strong grid structures.Furthermore,the characteristics of wind power dictate that wind turbines need to absorb reactive power during operation.Because of the strong correlation between voltage stability and systems' reactive power,the impacts of wind integration on voltage stability has become an important issue.Based on the power system simulation software DIgSILENT and combined analysis of actual practice,this paper investigates the impacts of two types of wind farms on voltage stability:namely a type of wind farms which are constituted by constant speed wind turbines based on common induction generators(IG) and another type of wind farms which are constituted by VSCF wind turbines based on doubly-fed induction generators(DFIG).Through investigation the critical fault clearing time is presented for different outputs of wind farms.Moreover,the impacts of static var compensator(SVC) and static synchronous compensator(STATCOM) on transient voltage stability in IG-based wind farms are studied to improve the security and stability of the Jiangsu power grid after the integration of large scale wind power.

Intelligent Wind Power Unit with Tandem Wind Rotors and Armatures （Optimization of Front Blade Profile）

The authors have invented the superior wind power unit, which is composed of the tandem wind rotors and the double rotational armature type generator without the traditional stator. The large-sized front wind rotor and the small-sized rear wind rotor drive, as for the upwind type, the inner and the outer rotational armatures, respectively, in keeping the rotational torque counter-balanced between both wind rotors/armatures. The unique rotational behaviors of the tandem wind rotors and the fundamental performances of the unit have been discussed at the previous paper. Continuously, this paper investigates experimentally and numerically the flow condition around the wind rotors to know the flow interactions between the front and the rear wind rotors, and optimizes the blade profile in the front wind rotor. The front blade should work fruitfully at the larger radius and had better not work at the smaller radius for giving plenty of wind energy to the rear wind rotor, taking account of the flow interaction between both wind rotors.

Torque Distribution Strategy for Integrated Starter/ Generator Hybrid Bus Implemented by Fuzzy Algorithm

A torque distribution strategy was designed by using fuzzy logic to realize the optimal control. The vehicle load zones were dynamically divided into several zones by several torque lines to indicate the drivers demand and the high or low efficient operating areas of the diesel engine. The fuzzy logic controller with trapezoid membership function and Mamdani rule reference mechanism was utilized. There are over 100 rules used in this fuzzy-based torque distribution strategy which are sorted into four rule-bases. The fuel economy and acceleration tests were designed to test and validate the integrated starter/generator (ISG) bus perfor-mance using fuzzy-based torque distribution strategy. The fuel economy is improved 7.7% compared with the rule-based strategy. Finally the road test results reveal that there is about 15% improvement of fuel economy. And the 0-50 km/h acceleration time is 9.5% shorter than the original bus.

MPPT for Hybrid Energy System Using Gradient Approximation and Matlab Simulink Approach

This paper applies new maximum-power-point tracking （MPPT） algorithm to a hybrid renewable energy system that combines both Wind-Turbine Generator （WTG） and Solar Photovoltaic （PV） Module （SPVM）. In this paper, the WTG is a direct-drive system and includes wind turbine, three-phase permanent magnet synchronous generator, three-phase full bridge rectifier, and buck-bust converter, while the SPVM consist of solar PV modules, buck converter, maximum power tracking system for both systems, and load. Several methods are applied to obtain maximum performances, the appropriate and most effective method is called gradient-approximation method for WTG approach, because it enables the generator to operate at variable wind speeds. Furthermore MPPT also is used to optimized the achieved energy generated by solar PV modules.Matlab / Simulink approach is used to simulate, discuss, and optimized the generated power by varying the duty cycle of the converters, and tip speed ratio of the WTG system.

Motion Performance and Mooring System of a Floating Offshore Wind Turbine

The development of offshore wind farms was originally carried out in shallow water areas with fixed （seabed mounted） structures. However, countries with limited shallow water areas require innovative floating platforms to deploy wind turbines offshore in order to harness wind energy to generate electricity in deep seas. The performances of motion and mooring system dynamics are vital to designing a cost effective and durable floating platform. This paper describes a numerical model to simulate dynamic behavior of a new semi-submersible type floating offshore wind turbine （FOWT） system. The wind turbine was modeled as a wind block with a certain thrust coefficient, and the hydrodynamics and mooting system dynamics of the platform were calculated by SESAM soRware. The effect of change in environmental conditions on the dynamic response of the system under wave and wind loading was examined. The results indicate that the semi-submersible concept has excellent performance and SESAM could be an effective tool for floating wind turbine design and analysis.

One Step on the Smart Grid Path： Load and Generation Coordination in a Virtual Power System

Worldwide the introduction of dispersed generators （DG） in the distribution network is assuming a significant importance. There is an increasing relevance of the energy process efficiency improvement; as for electric power systems, the most interesting perspective concerns the capability of the system to increase the exploitation of the renewable resources. The integration of DGs in the electric distribution network requires a revision of this infrastructure, so far designed and developed assuming that power flows in one direction： from the high voltage transmission network to the medium voltage distribution, to reach final customers on the low voltage network. The attention to an efficient operation of distribution networks is increasing all over the world; this interest is becoming higher and higher also in Italy, where the high energy prices push in the direction of fostering efficiency as much as possible. This work describes a study developed in the AlpEnergy project framework： an International Cooperation Program aimed at introducing an efficient operational model for the distributed production and consumption. In particular it is proposed a new model for the integration and the management of the DG in the distribution network. The new model （defined VPS： Virtual Power System） is based on a communication channel between the active users （generators）, the loads and, eventually, the Distribution System Operators （DSOs）.

Wind Energy Potential Assessment in Republic of Macedonia

The paper presents the measurement campaign of wind energy potential undertaken in Republic of Macedonia on four sites from the middle of 2006. The wind data analysis has been performed for one site, following with the assessment of energy production of simulated wind park with six wind turbine generators.

Research on Hybrid Renewable Energy Systems with Fault Detection Technology

Early and accurate fault detection and diagnosis for renewable energy systems can increase their safety and ensure the continuity of their service. This paper presents a comprehensive review of different fault detection and diagnosis methods for hybrid renewable energy systems consisting of a wind turbine power generator, a PV （photovoltaic） array, a PEM （polymer electrolyte membrane） fuel cell and a battery storage system. The need of batteries to store the generated power from the solar panel, wind turbine or PEM fuel cell is also emphasized. Finally, an overview of the current methods used in the diagnosing of the lead-acid battery degradation is given.

Aerodynamic Effects on TLP Type Wind Turbines and Predictions of the Electricity They Generate

This research proposes a new offshore wind energy generation system that uses a tension leg platform (TLP) and describes experiments performed on a TLP type wind turbine in both waves and wind. The following conclusions can be made from the results of this research. 1) In the case of coexisting wave-wind fields, the wind effect stabilizes the pitch motion. 2) The wind effect decreases vibration of the mooring lines when waves and wind coexist. In particular, the springing (2nd or 3rd order force) also decreases in this field. 3) It can be estimated that the reduction in the rate of generation of electrical power can be up to about 6% as a result of the heel angle. In addition, the annual amount of electricity generated was estimated along with the utilization factor based on the experimental results.