英文风电涡轮机分类分析及翻译.docx

1、英文风电涡轮机分类分析及翻译Comparison and Evaluation of Three Main Types of Wind Turbines 1Abstract Many different types of wind turbines have been connected to the power systems of the world in recent years, and their primary focus was to design them to be more efficient and reliable. In this paper, three main

2、types of wind turbines are modeled and compared. The performances of these wind turbines during a severe three-phase fault at the end of a transmission line are simulated and their characteristics are analyzed. Finally the operation and maintenance costs of these wind turbines are discussed and prop

3、er applications of these wind turbines are pointed out.Index Termswind turbine, modeling, fixed speed wind turbine, doubly fed induction generator, multipole permanent magnet synchronous generator。I. INTRODUCTION As the demand for energy is steadily increasing, experts have been looking for new form

4、s of resources to reduce dependence on fossil energy. Compared with solar and other renewable energy, wind energy is cheaper and more reliable. Over the years wind power became the most rapidly growing renewable energy in electricity generation . The installed capacity and net generation of wind pow

5、er in US from 1992 to 2005 are shown in Fig. 1. The total amount of electricity that could potentially be generated from wind in the United States has been estimated at 10.8 trillion kWh annually , but installed wind energy generating capacity now totals only 9,149 MW, and is expected to generate ab

6、out 24.8 billion kWh of electricity in 2006 that is still less than 1% of U.S. electricity generation (4.0 trillion kWh in 2004). According to Fig. 1, the average capacity factor of wind turbines is 21.7%, which is acceptable for a variable energy source with no fuel cost. As a practical green sourc

7、e, wind power can provide electric power with minimal environmental pollution. Compared to coal and natural gas, the wind source is renewable without any worry about the future depletion of wind reserve. But wind energy can provide only a part of the electrical demand and consumer cannot rely comple

8、tely on wind powered electric energy because wind is not available all the time. Experts have looked into the possibility of storing electrical energy. But as large scale electric energy storage is not cost effective, direct grid connected wind power is the most viable option. Fig. 1 Installed capac

9、ity and net generation of wind power in USSimilar to other generation processes, a wind turbine converts mechanical energy into generator torque and the generator converts this torque into electricity and feeds it into the grid. The difference is that the mechanical energy is from wind. A wind turbi

10、ne is a complex system because the knowledge from the areas of aerodynamics and mechanical, electrical, and control engineering is applied. To make the wind turbines more efficient and match the grid requirements better, more and more technologies are being applied to them. There are currently three

11、 main types of wind turbines available as shown in Fig. 2 :(a) Fixed speed wind turbine with an asynchronous squirrel cage induction generator (IG) directly connected to the grid via a transformer.(b) Variable speed wind turbine with a doubly fed induction generator (DFIG) and blade pitch control.(c

12、) Variable speed wind turbine using a permanent magnet synchronous generator that is connected to the grid through a full-scale frequency converter. This is called direct drive (DD) wind turbine.With the application of new technologies, the cost of electricity from utility-scale wind systems has dro

13、pped by more than 80% over the last 20 years. Now, state-of-the-art wind power plants at excellent sites are generating electricity at less than 5 cents/kWh, which is actual cost without other economic benefits such as production tax credit 2. Compared to the costs of conventional generation technol

14、ogies, it is very attractive and no other resources are needed to deal with expensive pollution emission control equipments. (a)(b)(c)(a) Fixed speed wind turbine with an induction generator(b) Variable-speed wind turbine with a doubly-fed induction generator(c) Variable-speed wind turbine with a pe

15、rmanent magnet synchronous generatorFig. 2 General structures of three different types of wind turbinesWind power will be looked at as same as a common electrical energy resource eventually, so the associated requirements of conventional generation technologies, such as power factor correction, supp

16、lying reactive power to the transmission system, stability improvement and so on, are being increasingly applied to wind turbines. Which type of wind turbine should be selected for a particular wind farm project is becoming one of the key issues in the decision making process. This paper introduces

17、the characteristics of the above mentioned three types of wind turbines and presents their mathematical models. Computer simulations of their responses to a severe three-phase to ground fault at the end of a transmission line are presented. Finally they are compared and discussed from both technical

18、 and economic points of view.II. BACKGROUNDAlthough utilization of wind power is increasing very fast in the world and the cost is decreasing rapidly, the main challenges are: the relatively high cost of producing a kWh, the reduction of capital cost of the wind turbine itself, and improving reliabi

19、lity.From the view of wind turbine design and manufacture, the cost of IG is the lowest because no power electronics devices are used. The voltage sag in the process of single phase fault is low in this type of generator. But its disadvantages are: it cannot run in wind gust, efficiency is low, and

20、it cannot control reactive power output, which is a very important requirement for power system voltage stability and quality. This is why IG is disappearing from the current markets.Compared to IG, which is connected to the grid directly, indirect grid connected wind turbines (including wind turbin

21、es with DFIG and DD（direct driver）) are much more efficient because they could be run at variable speed. Furthermore, indirect grid connected wind turbines can control reactive power to improve power quality for the electrical grid. This advantage is especially useful for a weak electrical grid, a v

22、ery common occurrence as wind farms are typically located at remote locations. This is why indirect grid connected wind turbines are widely used currently in spite of their high initial costs and complex control strategies.However, indirect grid connected wind turbines still need many improvements t

23、o compete with other conventional electricity generation technologies. Firstly, as Fig. 2 shows, the indirect grid connected wind turbines will need a rectifier and two inverters, one to control the stator current, and another to generate the output current. These power electronics devices cost 14%

24、of total initial project capital costs 5, but it may change as the cost of power electronics decreases. Secondly, there are energy losses associated with AC/DC/AC conversion process, and harmonic distortions of the alternating current may be introduced in the electrical grid by power electronics dev

25、ices, thus reducing power quality.To improve the performance of wind turbines, different technologies are being applied to them. Now two types of indirect grid connected wind turbines dominate the market. The DD type of wind turbines is mainly built by Enercon (Germany). This type of wind turbines i

26、s combined with synchronous permanent magnet generator and AC/DC/AC converter with a rating of 100% of the rated wind turbine power. Since it does not need the gear box, the weight at the hub height can be lowered a lot, and the operation and maintenance of the gear box are not needed. But because t

27、he capacity of the converter has to match the maximum output power of the generator, its cost is highest among all types of wind turbines. Also the generator is bigger than other types of wind turbines. In the long term, the operation and maintenance costs of the gear box can be saved.The other type

28、 of indirect grid connected wind turbine is a variable speed wind turbine with DFIG, which dominates the market with their total share to be around 84.5%-86%. The wind turbine with DFIG is combined with gear box, induction generator, and AC/DC/AC converter with a rating of only 20%30% of the rated w

29、ind turbine power. The cost of DFIG system is lower than the direct drive system because its power converter is approximately one-third the size of the direct drive system. But the control system of a DFIG is more complex than that of a DD.III. MODELINGA. Blade modeling (wind modeling)An aerodynamic

30、 model of the wind turbines is a common part of the dynamic models of the electricity-producing wind turbines. The captured aerodynamic power is given by:where P is the captured power from wind, is the air density, v is the wind speed, A is the swept area of the blade, C ( ) is the power coefficient

31、, is the ratio between blade tip speed and wind speed at hub height, is the pitch angle. C (, ) can be obtained from wind turbine manufacturers.B. Drive train modelingThe mechanical construction of the wind turbines is simply modeled as a lumped-mass system with the lumped combined inertia constant

32、of the turbine rotor and the generator rotor. The shaft dynamic equation is:where JT and JG are the inertia constant of the turbine rotor and the generator rotor, respectively, Ks and Ds are the shaft stiffness and damping constant respectively, angular speed, TG is the electrical twist angle of the shaft . T and G are the angular speeds of shaft at the ends of turbine and generator, respectively, TT and TE are the mechanical and electrical torque, respectively.C. Generator modelingAs mentioned earlier, there are three types of generators used in wind turb