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1、WIND POWER GENERATION1.INTRODUCTIONThere is continuing interest in wind turbines, especially those with a rated power of many megawatts. This popularity is largely driven by both environmental concerns and also the availability of fossil fuels. Legislation to encourage the reduction of the so called
2、 carbon footprint is currently in place and so interest in renewablesis currently high. Wind turbines are still viewed as a well established technology that has developed from fixed speed wind turbines to the now popular variable speed technology based on doubly-fed induction generators. ADFIG wind
3、turbine is variable speed with the rotor converter being controlled so that the rotor voltage phase and magnitude is adjusted to maintain the optimum torque and necessarystator power factor. DFIG technology is currently well developed and is commonly used in wind turbines. The stator of a DFIG is di
4、rectly connected to the grid with a power electronic rotor converter utilized between the rotor winding and the grid. The variable speed range is proportional to the rating of the rotor converter and so by limiting the speed range to +-30%the rotor converter need only be rated for 30% of the total D
5、FIG power whilst enabling full control over the full generator output power. This can result in significant cost savings for the rotor converter. The slip ring connection to the rotor winding however must be maintained for reliable performance.The power-generator speed characteristic shown in figure
6、 1 is for a commercial 2MW wind turbine. The generator speed varies with wind speed however this relation is set for a specific location. As wind speed, and therefore machine speed, falls the power output of the generator reduces until the wind turbine is switched off when the power extracted from t
7、he wind is less than the losses of the generator and converter. An operating mode has been proposed by a wind turbine manufacturer that is claimed to extend the speed range so that at lower speed the power extracted from the wind is greater than the losses in the system and so the system can remain
8、connected. This proposed that the standard doubly-fed connection is used over the normal DF speed range and the so-called induction generator mode is used to extend the low speed operation. Previous work has illustrated that IG mode enables the DFIG to operate down to 80% slip. This change in operat
9、ion is achieved by disconnecting the stator from the grid in DF mode and then short circuiting the stator to enable IG operation. All of the generator power flows through the rotor converter in IG mode. The IG curve is identical to the DF curve for +-30%slip. The estimated IG power extracted from th
10、e wind at low speeds is obtained by extrapolating the curve for the DF mode.The reference torque required by both controllers can easily be derived from this curve. The torque-speed data can then be stored in a look-up table so the reference torque is automatically varied with speed. The capability
11、of modern DF wind turbines to vary the reactive power absorbed or generated allows a wind turbine to participate in the reactive power balance of the grid. The reactive power at the grid connection considered in this work is described, for the UK, by the Connections Section CC. available from the Na
12、tional Grid. The reactive power requirement for a wind farm is defined by figure2.Point A-MV Ar equivalent for 0.95 leading power factor at rated MWPoint B-MV Ar equivalent for 0.95 lagging power factor at rated MWPoint C-MVAr-5% of rated MWPoint D-MV Ar 5% of rated MWPoint E-MVAAr-12% of rated MWTh
13、e objective of this paper is to investigate the controller performance of DF and IG mode for a 2MW,690V, 4-pole DFIG using machine parameters provided by the manufacturer. This is further research building on a previous paper which demonstrated the steady-state performance of the two modes of operat
14、ion, DF and IG mode 8. In 8 the authors discussed the steady-state efficiency for both connections. The steady0state performance work illustrated that there were benefits to operating the machine in one connection method as opposed to the other.This paper examines the controllability of the 2MW wind
15、 turbine. Results of the full dynamic controller in both DF mode and IG mode are shown. A detailed analysis of the components that form the rotor voltage over the full operating range in DFIG mode is presented as this enables the dominant control components to be identified. This is particularly imp
16、ortant when designing advanced control schemes as an overview over the full operating range can be identified.Simulation models, which have been validated against a 7.5KW laboratory rig , are applied to a realistic 2MW wind turbine to enable conclusions to made regarding the proposed use of IG mode
17、in a real wind turbine.2.CONNECTION METHODSDoubly-fed induction machines are commonly connected as shown in figure 3.The grid side inverter is controlled to maintain a fixed dc link voltage with a given power factor at the grid. The rotor side inverter is controlled so the maximum energy is extracte
18、d from the kinetic energy of the wind whilst enabling the stator power factor to be controlled within the limits of the grid requirements though unity power factor is often desirable.An alternative connection method for a doubly-fed machine is shown in figure 4,here called the induction generator co
19、nnection. The stator is disconnected from the grid and is short-circuited. The rotor circuit is unchanged from figure 3.The GSI is controlled as in DF mode. The objective of the RSI is to control the stator flux linkage while extracting the maximum power from the kinetic wind energy.3.CONTROLLER PER
20、FORMANCEA closed loop controller for both DF mode and IG mode has been discussed in prior work but only for a 7.5kw laboratory test rig. The dynamics of a 2MW system are somewhat different and are investigated in this paper. The performance of the dynamic controller for both DF and IG mode are shown
21、 in this section for a 2 MW wind turbine.3.1 DFIG ModeThe reference values for the controller in DF mode are torque and stator reactive power to enable the grid code requirement to be achieved, figure 2. Two speeds are investigated in this section to enable the performance of the controller to be sh
22、own both above and below the 20%of rated power limit from the grid code requirements. A nominal generated power of 320kw is achieved at 1150 rpm and a nominal power of 1.25 MW is achieved at 1550 rpm. The reference and actual torque, Te, and stator reactive power, Qs, are shown for both speeds. In f
23、igure 5.SolarSolar energy is renewable energy .It is rich in resources ,can use free of change , and without transportation, without any pollution to the environment .For mankind to create a newlife, so that social and humanenergy into a era of reducing pollution.Solar energy has become increasingly
24、 widespread use, it includes the use of solar energy solar thermal, solar photovoltaic and solar energy use, such as the photochemical use. The use of solar photochemical reaction, a passive use and the photoelectric conversion in two ways. A newsolar power and renewable sources of energy use.Silico
25、n photovoltaic cells mainly in the absorption of solar light energy emitted by silicon photocell is mainly extracted from the sand by the development of Bell Labs. Solar energy is the internal or the surface of the sun sunspot continuous process of nuclear fusion reactions produce energy. Earth'
26、sorbit on the average solar radiation intensity for the 1367W/ m2. Circumferenee of the Earth ' s equator to 40000km, and thus calculated the Earth ' s energy can be obtained 173000TW 。 At sea level standard for peak intensity 1KW/m， a point on theEarth ' s surface 24h of the annual aver
27、age radiation intensity 0.20KWWm/ , which is equivalent to have 102000TW energy.Human dependenceon these energy to survive, including all other forms of renewable energy, although the total amount of solar energy resources is the human equivalent of the energy used by ten thousand times, but low ene
28、rgy density of solar energy, and it vary from place to place, from time to time change, the development and utilization of solar energy which is facing a major problem. These features will make solar energy in the integrated energy system of the role of subject to certain restrictions.The use of sol
29、ar cells, through the photoelectric conversion to solar energy conversion is included in electricity, the use of solar water heaters, the use of solar heat hot water and use water for power generation, using solar energy for desalination. Now, the use of solar energy is not very popular, the use of
30、solar power costs are high there, the problem of low conversion efficiency, but for satellite solar cells to provide energy has been applied.Although the Earth ' s atmosphere solar radiation to the total energy only 22 billionths of a radiation energy, it has been as high as 173 ，000TW，that is t
31、o say a second exposure to the sun ' s energy on Earth is equivalent to five million tons of coal. Earth wind energy, hydropower, ocean thermal energy, wave energy and tidal energy as well as somecomes from the sun; even in the face of the earth' s fossil fuels that isfundamentally Since anc
32、ient times the storage of solar energy down, so by including a broad range of solar energy is verylarge.The narrow sense is limited to solar radiation of solar light thermal, photovoltaic and photochemical conversion of the directly .Solar cells can convert solar energy to power the device. Photovol
33、taic effect can produce many kinds of materials, such as: single crystal silicon, polycrystalline silicon, amorphous silicon, gallium arsenide, copper indium selenium. They are basically the sameprinciple of power generation is nowcrystal as an example to describe the process of light generation. P-
34、type crystalline silicon available after phosphorus-doped N-type silicon, the formation of P-N junction.Whenthe surface of solar light, the silicon material to be part of photon absorption; photon energy transfer to the silicon atom, electronic transitions have taken place, as a free-electron concen
35、tration in the PN junction formed on both sides of the potential difference, when the external circuit connected when the effects of the voltage, there will be a current flowing through the external circuit have a certain amount of output power, The substance of this process are: photon energy into
36、electrical energy conversion process.“Si ” is our planet' s abundance of storage materials.Since the 19th century, scientists discovered the properties of crystalline silicon semiconductor, it almost changed everything, even human thought, end of the 20th century. Ourlives can be seen everywhere
37、,“ silicon ” figure and role ofcrystalline silicon solar cells is the formation of the past 15 years the fastest growing industry. Production process can be divided into five steps: a, purification process b, the process of pulling rod c, slicing the process of d, the process of system battery e, th
38、e course package.Solar photovoltaicIs a component of photovoltaic panels in the sun exposure will generate direct current power generation devices, from virtually all semiconductor materials are made of thin photovoltaic cells composed of solid. Because there is mopart of activity, and would thus be
39、 a long time operation would not lead to any loss. Simple photovoltaic cells for watches and computers to provide energy, and more complex PV systems to provide lighting for the housing and power suppl7u. Photovoltaic panels can be made into components of different shapes, and components can be conn
40、ected to generate more power. In recent years, the surface of the roof and building will be the use of photovoltaic panels components.Even be used as windows, skylights or sheltered part of devices, which are often called photovoltaic facilities with PV systems in buildings.Solar thermalModern techn
41、ology solar thermal polymerization sunlight and use its energy produced hot water, steam and electricity. In addition to the use of appropriate technology to collect solar energy, the building can also make use of the sun's light andheat energy is added in the design of appropriate equipment, su
42、ch as large windows or use of the south can absorb and slowly release the sun heat the building materials.According to records, humanuse of solar energy has more than 3000 years of history. To solar energy as an energy and power use, only 300 years of history. To solar energy as an energy and power
43、use, only 300 years of history. The real solar as “the near future to add much-needed energy,” ”the basis of thefuture energy mix ” is the latest thing. Since the 20th century, 70s, solar technology has maderapid advances, solar energy use with each passing day. Solar energy utilization in modern hi
44、story from the French engineers in 1615 in the Solomon and Germany Cox invented the world 's first solar-powered engines run. The invention is a use of solar energy heating the air tothe expansion and pumping machines acting.In 1615-1900, between the developed world and more than one solar power
45、 plant and a number of other solar energy devices. Almost all of these power plants collect the sun means the use of condenser, engine power is not, the working fluid is water vapor, which is very expensive, not practical value, the majority of individual studies for manufacturing solar enthusiasts. 100 years of the 20th century, the history of thedevelopment of solar energy technology in general can be divided into seven stages.