风力发电外文文献翻译中英文
毕业设计风力发电外文文献
Abstract--The purpose of this paper is to find an innovative, high efficiency, practical and low cost control system structure with an optimized control strategy for small-scale grid-connected wind turbine with direct-driven permanent magnet synchronous generator (PMSG). This research adopts the sensorless vector control strategy based on phase-locked loop (PLL) for PMSG control, and the grid-side inverter control strategy is based on the single-phase PLL. The simulation demonstrates that the sensorless control strategy and single-phase grid-side inverter control strategy are practical solutions for grid-connected PMSG wind turbines, and they can provide both generator speed control for optimized wind power tracking and good power quality control for electricity delivered to the grid. The designed system offers many unique advantages, including simple topology, optimized control strategy, cost-effective and fast respond to grid failures.Index Terms--Maximum power point tracking (MPPT), PMSG, pulse-width modulation (PWM) converter, speed control, variable-speed wind turbine.I. I NTRODUCTIONn recent years, great attention has been paid on renewable energy sources, such as wind and solar energy. Wind energy is the most popular renewable energy source due to its relatively low cost. The overall system cost can be further reduced by optimal control of high efficiency power electronic converters to extract maximum power in accordance with atmospheric conditions [11].The wind energy conversion system based on permanent magnet synchronous generator (PMSG) is one of the most favorable and reliable methods of power generation. Reliability of variable-speed direct-driven PMSG wind turbines can be improved significantly comparing to doubly-fed induction generator (DFIG) wind turbines with gearboxes. Noise, power loss, additional cost, and potential mechanical failure are typical problems for a DFIG wind turbine because of the existence of a gearbox. The use of direct-driven PMSG could solve these problems. Moreover, low voltage ride through (LVRT) is also a big issue for DFIG because the This work was supported in part by the special funds from Beijing Municipal Education Commission.Chunxue Wen, Guojie Lu, Peng Wang and Zhengxi Li are with the Power Electronics and Motor Drivers Engineering Research Centre, North China University of Technology,Beijing,China(e-mail: wenchx1980@, lugod307@, catdapeng2008@, lzx@).Xiongwei Liu and Zaiming Fan are with the School of Computing, Engineering and Physical Sciences, University of Central Lancashire, Preston, PR1 2HE, UK (e-mail: xliu9@, zmfan@) electromagnetic relationship between the stator and the rotor is more complex than PMSG. Therefore, it’s more difficult for DFIG to solve LVRT problem safely and reliably.In a variable-speed PMSG system, vector control approach is often used to achieve nearly decoupled active and reactive power control on the grid-side inverter which is a current regulated voltage source inverter. In this way, the power converter maintains the DC-link voltage and improves the power factor of the system [1], [7], [10]. Different control methods for maximum power point tracking (MPPT) in variable-speed wind turbine generators have been discussed in [2], [4], [7].This research adopts the sensorless vector control strategy based on phase-locked loop (PLL) for PMSG control [2]. The method requires only one active switching device, i.e. insulated-gate bipolar transistor (IGBT), which is used to control the generator torque and speed so as to extract maximum wind power. It is a simple topology and low cost solution for a small-scale wind turbine because of the sensorless vector control strategy. The grid-side inverter control strategy is based on the single-phase PLL, which applies a control method in Direct-Quadrature (DQ) rotating frame to single-phase inverter and achieves superior steady state and dynamic performance [6].For small-scale wind turbine, single-phase power supply to consumers is popular. There are many control methods for single-phase inverter, such as PI controller, quasi-PR controller, etc. [5]. However, these methods can’t decouple the active power and reactive power so as to have good power control performance. Single-phase PLL method based on DQ rotating frame can well solve this problem. On the other hand, encoders are vulnerable components for wind turbines, particularly for small wind turbines, because small wind turbines experience severer vibrations than their large counterparts. The sensorless vector control opts out the encoders, and therefore the reliability of wind turbines is much improved. For these reasons, the sensorless vector control and single-phase PLL method have their unique advantages for small-scale wind turbines.This paper is structured further in following three sections. In section II, the principle of the full power back-to-back PWM converter is introduced. Then the vector control of small-scale grid-connected wind power system including sensorless control, vector control of PMSG, single-phase PLL, vector control of grid-side inverter are described in section III. Finally, in section IV, the simulation results and conclusion are given.Vector control strategy for small-scale grid-connected PMSG wind turbine converter Chunxue Wen, Guojie Lu, Peng Wang, Zhengxi Li Member IEEE, Xiongwei Liu Member IEEE,Zaiming Fan Student Member IEEEIII. T HE PRINCIPLE OF FULL POWER BACK-TO-BACK PWMCONVERTERTypical topology model of direct-driven PMSG wind turbine is shown in Fig. 1. Converters of the system adopt back-to-back pairs of pulse-width modulation (PWM) architecture. The generator-side converter controls the generator speed in order to achieve maximum capture of wind power, and the grid-side inverter controls the stability of DC-bus voltage and the power factor of the system. This topology can be a good way to improve performance, and the control method is flexible. Converters have four-quadrant operation function, which can fulfill the generator speed control anddeliver the fine quality of electricity to the grid [7], [8].Fig. 1. Topology of permanent magnet direct-driven wind power systemIII. T HE VECTOR CONTROL OF SMALL-SCALE GRID-CONNECTEDDIRECT-DRIVEN WIND POWER SYSTEM CONVERTERFig. 2 shows the back-to-back PWM voltage convertervector control block diagram. The machine-side PWMconverter controls the electromagnetic torque and statorreactive power (reactive power is often be set to 0) byadjusting the current of the d-axis and q-axis of the machine-side converter. This control mechanism helps the PMSG tooperate in variable speed, so that the wind turbine can workwith maximum power point tracking (MPPT) under the ratedwind speed. The grid-side PWM inverter stabilizes the DC-busvoltage and accomplishes active and reactive decouplingcontrol by adjusting the current of the d-axis and q-axis of thegrid-side. The grid-side PWM inverter also controls thereactive power flow to the grid, usually at unity power factorcondition.A. Sensorless control based on PLLThe speed and position control is achieved throughsensorless vector control of the machine-side converter basedon all-digital phase-locked loop. The phase-locked loop isdesigned to control the frequency of the D-Q axis voltagethrough minimizing the difference of the output voltage phaseangle and the given voltage phase angle, until the outputvoltage phase angle tracks the given voltage phase angle. Asthe phase-locked loop has frequency closed-loop trackingmechanism, the generator voltage frequency and the anglebetween d-axis voltage and rotor flux can be measured withthis characteristic, then the generator speed and rotor positionangle can be derived [2]. The control accuracy is generallygood using this method, however some problems may occurwhen the generator operates at very low speed. The windpower system often works above the cut-in wind speed, so thismethod can be applied to wind power generation system.Fig. 2.The back-to-back PWM voltage converter vector control block diagramThe actual rotor position of PMSG is indicated in the D-Q coordinate system. The estimated location for ∧θ is the d q ∧∧− coordinate system, αβ is the stationary coordinate system, as shown in Fig. 3. As the rotor position of PMSG is estimated rather than measured in the sensorless vector control system, there exists an error θΔ between the actual rotor position θ and the estimated location ∧θ. At the same time, the back-EMF (electromotive force) generated by the rotor permanent magnets generates two d-axis and q-axis components in the estimated rotor position orientation coordinates, which are expressed as sd e ∧and sq e ∧respectively. Conventional PI controller can achieve zero error control, i.e. sd e ∧or θΔ can be adjusted to zero value. The PLL sensorless vector control schematic diagram is shown in Fig. 4, and the value of sd e ∧and sq e ∧can be obtained from (1).sd sd s sd dq sq sd sq sq s sq q d sd sq di u R i L L i e dt di u R i L L i e dt ωω∧∧∧∧∧∧⎧=+−−⎪⎪⎨⎪=+++⎪⎩(1)Fig. 3. Presumed rotating coordinate systemFig. 4. Principle of PLL based sensorless vector controlIf we ignore the current differential items in (1), then wehavesd s sd q sq sd sq sq s sq d sd ˆˆˆˆˆarctan(arctan(ˆˆˆˆˆu R i L i ee uR i L i ωθω−+Δ=−=−−− (2)where sd u , sq u , sd i and sq i are the d, q-axis components of the output voltage and current of the generator stator; d L q L and s R are the inductance and resistance of the stator; ω is thegenerator electrical angular velocity of the generator; "∧" indicates estimated value.Block diagram of sensorless vector control based on digital PLL is shown in Fig. 5. The back-EMF (electromotive force) value of the estimated rotating coordinates can be obtained by calculating the three-phase voltages and currents of the PMSGstator. The calculated angle difference θΔcan be used to estimate the angular velocity through the PI controller. Then the value of the estimated angle can be obtained by integral element. Generally, the speed has considerable fluctuations using this method. Therefore it will achieve a better estimation by adding a low-pass filter (LPF), as shown in Fig. 5.∧Fig. 5. Block diagram of sensorless vector control based on digital PLLB. Vector control of PMSGIn order to study the torque control of PMSG, it is necessary to establish a mathematical model. Because q-axis leads d-axis 90° in the D-Q coordinate system, the generator voltage equation can be expressed as [8]: sd sd s sd d sq sq sq sq sq q d sd di u R i L L i dt di u Ri L L i dt ωωωψ⎧=+−⎪⎪⎨⎪=+++⎪⎩(3) The significance of various physical quantities in (3) is the same as in (1).The generator electromagnetic torque equation can be expressed as:33()22e sq d q sd sq T p i p L L i i ψ=+− (4) where p is the number of generator pole pairs, and ψ is the magnetic flux.Based on the above mathematical model, the sensorless vector control program of PMSG is established, and its controlblock diagram is shown in Fig. 6.sa i sbi Fig. 6. Sensorless vector control block diagram of PMSGGenerator rotor position and speed which are estimated by sensorless algorithm can be used in vector control. Thereference value of motor torque can be obtained by the speedcontroller. The voltage reference of generator can also be gotby current controller, and then the control signals of rectifier switching device can be obtained by a set of PWM modulation algorithms. The position and speed of generator rotor which is necessary to vector control is obtained by sensorless algorithm.C. Single-phase grid-connected PLLFig. 7 shows the block diagram of the single-phase gird-connected PLL. In order to ensure that the converter outputvoltage is in the same phase with the output current, the PLLis used to achieve unity power factor control. At the sametime, the converter also provides the angle of the referencecurrent transformation [5].Fig. 7. The block diagram of the single-phase PLLThe transformation between orthogonal a-b and D-Q reference frames can be described by trigonometric relations, which are given in (5) and (6), and the rotating reference frame is shown in Fig. 8.Fig. 8. Definition of rotating reference frame⎥⎦⎤⎢⎣⎡⎥⎦⎤⎢⎣⎡−=⎥⎦⎤⎢⎣⎡b a q d f f f f θθθθcos sin sin cos (5) ⎥⎦⎤⎢⎣⎡⎥⎦⎤⎢⎣⎡−=⎥⎦⎤⎢⎣⎡q d b a f f f f θθθθcos sin sin cos (6)Active power and reactive power equations can beexpressed as:⎩⎨⎧−=+=d q q d qq d d i v i v Q i v i v P (7) If the phase voltage and q-axis coincide, then 0=d v andv v q =, active power and reactive power equations can besimplified as:||||q dP v i Q v i =⎧⎪⎨=−⎪⎩ (8) D. The vector control strategy of the grid-side inverterFor a three phase converter, simple PI compensators designed in a D-Q synchronous frame can achieve zero steady state error at the fundamental frequency, but this method is not applicable to single-phase power converter because there is only one phase variable available in a single-phase power converter, while the D-Q transformation needs at least two orthogonal variables.In order to construct the additional orthogonal phaseinformation from the original single-phase power converter,the imaginary orthogonal circuit is developed, as shown inFig. 9. The imaginary orthogonal circuit has exactly the samecircuit components and parameters, but the current b i and the voltage b e , maintain 90D phase shift with respect to their counterparts in the real circuit- a i and a e [6].Fig. 9. Real circuit and its imaginary orthogonal circuitFrom Fig. 9, the voltage equation can be expressed as:⎥⎦⎤⎢⎣⎡−−+⎥⎦⎤⎢⎣⎡⎥⎦⎤⎢⎣⎡−=⎥⎦⎤⎢⎣⎡b b a a b a b a v e v e L i i L R i i p 11001 (9) Transforming the voltage equations into the synchronousreference frame using (5) and (6), and considering 0=d v and v v q =, we have: ⎥⎦⎤⎢⎣⎡−+⎥⎦⎤⎢⎣⎡⎥⎦⎤⎢⎣⎡−−−=⎥⎦⎤⎢⎣⎡||1//v e e L i i L R L R i i p qd q d q d ωω (10) To achieve decoupled control of active power and reactive power, the output voltage of the inverter in the synchronousreference frame can be expressed as:||)(1v i x L e d q +−=ω (11))(2q d i x L e ω+= (12)Substituting (11) and (12) into (10), system equations canbe rewritten as follows:⎥⎦⎤⎢⎣⎡+⎥⎦⎤⎢⎣⎡⎥⎦⎤⎢⎣⎡−=⎥⎦⎤⎢⎣⎡211001x x i i L R i i p q d q d (13) The active power and reactive power could be controlled by d i and q i respectively. Therefore, system control can be completed by current feedback loops as follows:))((211q q i i s k k x −+=∗(14)))((212d d i i sk k x −+=∗(15) Fig. 10 shows the control block diagram of the grid-sideinverter. It should be noted that the given active and reactive power should be set at two times of the desired values, because the imaginary circuit will not deliver any active andreactive power to the grid.θωFig. 10. The vector control block diagram of the grid-side inverterIV. S IMULATION RESULTSA simulation model in Matlab/Simulink is developed based on above theoretical analysis, and the system simulation block diagram is shown in Fig. 11.Fig. 11. The system simulation block diagramA. The simulation results of the machine-side converterIn the simulation model, the Reference speed represents the wind speed. At the beginning of the simulation (i.e. 0s), the generator speed is 4rpm and its input torque is -50Nm. At the time of 0.5s, the generator speed is 17 rpm and the input torque maintains at the value of -50Nm. At 1s, the generator speed maintains at 17 rpm and the input torque is -80Nm. The simulated waveforms are shown in Fig. 12, Fig. 13, Fig. 14, Fig. 15, respectively.It can be seen from Fig. 12 and Fig. 13, the error between the estimated rotor position angle and the actual measurement of the rotor position angle is very small in the steady state, there are some fluctuations in the dynamic response, but the rotor position angle is stabilized quickly.It can be seen from Fig. 14 and Fig. 15, there is a small error between the estimated and measured generator rotor speed at low speed. At high speed, however, the error is very small and can be ignored, and the transient response is very short. At the time 1s, the input torque increase affects thegenerator rotor speed slightly, and soon the transientdisappears.ˆ,(d e g )θθ()t sFig. 12. The estimated and measured rotor position angle(rad/s)θθ∧−(s)tFig. 13. The error of estimated and measured rotor position anglet(s)()nrpmFig. 14. The measured generator rotor speedt(s)t()esirpmnFig. 15. The estimated generator rotor speedThe simulation waveforms of the machine-side converterdemonstrate that the sensorless vector control algorithm canestimate the rotor angular position accurately, and the vectorcontrol strategy of the machine-side converter can realizegenerator speed control for the wind turbine to follow theoptimized power curve, i.e. MPPT when the wind speed isbelow rated wind speed.B. The simulation results of the grid-side inverterThe simulation results of the grid-side inverter is shown inFig. 16, Fig. 17 and Fig. 18 respectively.It can be seen from Fig. 16, when the generator outputtorque increases, the DC bus voltage is maintained constant.Fig. 17 shows that θu followsavvery well, and Fig. 18shows thatai followsavvery well.Fig. 16. The simulated DC voltageavuθuθFig. 17. The generator output A phase voltage and the grid voltage vectorangleFig. 18. The output voltage and current of the grid-side inverterFrom the simulation results of the grid-side inverter, it canbe seen that the single-phase PLL algorithm can accuratelytrack the grid-side voltage, and the vector control strategy ofthe grid-side inverter can stabilize the DC bus voltage, andcontrol the grid power factor.V. C ONCLUSIONThis research developed a power electronic converter for asmall direct-driven PMSG wind turbine using the back-to-back pulse-width modulation (PWM) topology. Thesimulation results demonstrate that1) The machine-side converter can control the generatorspeed and torque for the wind turbine to follow the optimizedpower curve, i.e. maximum power point tracking (MPPT)when the wind speed is below rated wind speed.2) The sensorless phase-locked loop (PLL) controlalgorithm can realize the vector control of the generator.3) The grid-side inverter control algorithm based on single-phase PLL can stabilize the DC bus voltage of the converter and control the grid power factor.VI. R EFERENCESPeriodicals:[1]De Tian, “The wind power technology status and development trend inthe world,” New Energy Industry, in press.[2]Ruzhen Dou, Lingyun Gu, Baotao Ning, “Sensorless control of thePMSM based on the PLL,” Electric Machines & Control Application, vol. 32, pp. 53-57, 2005.Books:[3]Qingding Guo, Yibiao Sun, Limei Wang, Modern permanent magnet ACservo motor system. China Electric Power Press, Beijing. In press.Papers from Conference Proceedings (Published):[4]S. Song, S. Kang, and N. Hahm, “Implementation and control of gridconnected AC-DC-AC power converter for variable speed wind energy conversion system,” in Proc. 2003 IEEE Applied Power Electronics Conference and Exposition, vol.1, pp.154 – 158.[5]M. Ciobotaru, R. Teodorescu and F. Blaabjerg, “A new single-phasePLL structure based on second order generalized integrator,” Record of IEEE PESC 2006, Korea, pp.1511-1516.[6]R. Zhang, M. Cardinal, P. Szczesny, M. Dame, “A grid simulator withcontrol of single-phase power converters in D-Q rotating frame,” Power Electronics Specialists Conference, vol.3, pp.1431 – 1436, 23-27 June 2002.[7]R. Esmail, L. Xu, D.K. Nichols, “A new control method of permanentmagnet generator for maximum power tracking in wind turbine application,” IEEE Power Engineering Society Meeting, vol.3, pp. 2090-2095, August 2005.[8]Yang Zhenkun, Liang Hui, “A DSP control system for the gridconnected inverter in wind energy conversion system,” IEEE ICEMS 2005 Electrical Machines and Systems, vol. 2, 2005, pp. 1050-1053, June 2005.[9]N V Suresh Kumar Srighakollapu, Partha Sarathi Sensarma, “Sensorlessmaximum power point tracking control in wind energy generation using permanent magnet synchronous generator,” Industrial Electronics 2008, 34th Annual Conference Of IEEE, Iecon , pp.2225-2230.Dissertations:[10]Cheng Lu, “The coordination control of dual PWM converter for VSCFwind power generation system,” MSc thesis, Graduate School of Chinese Academy of Sciences, Beijing, 2004.[11]Shenbing Wu, “Research on CSC-based small-scale grid-connectedwind power generation system”, MSc thesis, Hefei University of Technology, Hefei, 2009.VII. B IOGRAPHIESChunxue Wen received his BSc degree from Inner Mongolia University of Technology in 2001, MSc degree from Wuhan University in 2006, and PhD degree from the Institute of Electrical Engineering, Chinese Academy of Sciences in 2009. In 2010 he joined the Wind Energy Engineering Research Group at the University of Central Lancashire as a visiting researcher. He is currently working as a Lecturer at the Power Electronics and Motor Drivers Engineering Research Center, North China University of Technology, Beijing, China. His research interests include power electronics, wind turbine control system, converters for wind turbines.Guojie Lu received his BSc degree from North China Electric Power University in 2006. He worked in Beijing Xinhuadu Special Transformer Company from 2007 to 2009, and was responsible for the technical service transformer. At present, he is registered as a postgraduate research student at the Power Electronics and Motor Drivers Engineering Research Center, North China University of Technology, Beijing, China. His research area is wind turbine control system.The project aims to develop maximum power point tracking control algorithm for grid-connected small wind turbines.Peng Wang received his BSc degree from Taiyuan University of Technology in 2003, MSc degree from North China University of Technology in 2011. Since 2008, he has been working as a research assistant in Electrical Engineering at the Power Electronics and Motor Drivers Engineering Research Center, North China University of Technology, Beijing, China. In 2010 he joined the Wind Energy Engineering Research Group at the University of Central Lancashire as a visiting student. His research areas are permanent-magnet synchronous generator control and wind energy engineering.Zhengxi Li received his PhD degree from the University of Science and Technology, Beijing. He is the Chair Professor in Power Electronics and Motor Drivers and Head of the Power Electronics and Motor Drivers Engineering Research Center, North China University of Technology, Beijing, China. He is also Vice President of North China University of Technology. His research interests include power electronics, high voltage power transmission and distribution, intelligent transportation and renewable energy. Xiongwei Liu was born in Xiangtan, China, in 1965. He received his BEng (Hons) degree from National University of Defense Technology, Changsha, in 1985, and his MSc (Distinction) and PhD degrees from Harbin Institute of Technology in 1988 and 1991 respectively.His employment experience included Northwestern Polytechnical University, Huaqiao University, Leeds Met University, University of Hertforshire and University of Central Lancashire. His research interests include wind energy engineering, renewable energy technologies, smart grid and microgrid, and intelligent energy management system.He received a research fellowship from Alexander-von-Humboldt Foundation of Germany, which allowed him to visit Ruhr University Bochum, as a research fellow for 18 months from 1993. In 1999 he was awarded a Bronze Medal by Huo Yingdong Education Funding Council and a Model Worker Medal by the Mayor of Quanzhou, China, due to his excellent contributions in higher education when he served as a professor at Huaqiao University. He received a research fellowship from Chinese Scholarship Council, which allowed him to visit Technical University Berlin as a senior research fellow for 6 months in 2000.Xiongwei Liu is currently working as Chair Professor of Energy and Power Management and Head of Wind Energy Engineering Research Group at the University of Central Lancashire.。
风力发电英文作文
风力发电英文作文Wind power generation is a clean and renewable energy source that harnesses the power of the wind to generate electricity. It is a sustainable alternative to traditional fossil fuels and has the potential to reduce greenhouse gas emissions and combat climate change.The use of wind turbines to capture the kinetic energyof the wind and convert it into electricity has beengrowing rapidly in recent years. Wind power generation has the advantage of being able to produce electricity without the release of harmful pollutants or greenhouse gases, making it an environmentally friendly energy source.One of the key benefits of wind power generation is its ability to provide electricity to remote and off-grid areas. Wind turbines can be installed in locations wheretraditional power infrastructure is not available, bringing electricity to communities that would otherwise havelimited access to energy.In addition to its environmental benefits, wind power generation also has the potential to create jobs and stimulate economic growth. The development, installation, and maintenance of wind turbines require skilled labor, creating employment opportunities in the renewable energy sector.Despite its many advantages, wind power generation also faces challenges. One of the main challenges is the intermittent nature of wind energy, as the wind does not blow consistently. This variability in wind speed can make it difficult to rely solely on wind power generation for electricity supply.In conclusion, wind power generation is a promising and sustainable energy source that has the potential to play a significant role in the transition to a low-carbon economy. With ongoing technological advancements and investment in wind energy infrastructure, it is likely to become an increasingly important part of the global energy mix.。
风力发电英文作文
风力发电英文作文英文：Wind power is a renewable energy source that has gained popularity in recent years. It involves the use of wind turbines to generate electricity, which can then be used to power homes, businesses, and even entire cities. One of the benefits of wind power is that it is clean and does not produce any harmful emissions, unlike fossil fuels.Another advantage of wind power is that it is cost-effective. While the initial investment in wind turbines can be high, the cost of producing electricity from wind power is much lower than that of traditional power sources. This is because wind is a free and abundant resource, and once the turbines are installed, the cost of producing electricity is relatively low.In addition to being a clean and cost-effective energy source, wind power also has the potential to create jobsand stimulate economic growth. The construction and maintenance of wind turbines require skilled workers, and the development of wind farms can create new opportunities for businesses and entrepreneurs.However, there are also some challenges associated with wind power. One of the biggest challenges is that wind is an intermittent energy source, meaning that it is not always available. This can make it difficult to rely solely on wind power to meet energy needs. Additionally, wind turbines can be noisy and can have negative impacts on wildlife and their habitats.Despite these challenges, wind power is still a promising energy source that has the potential to play a significant role in our transition to a more sustainable future.中文：风力发电是一种可再生能源，近年来受到了广泛的关注。
风力发电外文文献翻译中英文
风力发电外文翻译中英文英文Wind power in China – Dream or reality?HubacekAbstractAfter tremendous growth of wind power generation capacity in recent years, China now has 44.7 GW of wind-derived power. Despite the recent growth rates and promises of a bright future, two important issues - the capability of the grid infrastructure and the availability of backup systems - must be critically discussed and tackled in the medium term.The study shows that only a relatively small share of investment goes towards improving and extending the electricity infrastructure which is a precondition for transmitting clean wind energy to the end users. In addition, the backup systems are either geographically too remote from the potential wind power sites or currently financially infeasible. Finally, the introduction of wind power to the coal-dominated energy production system is not problem-free. Frequent ramp ups and downs of coal-fired plants lead to lower energy efficiency and higher emissions, which are likely to negate some of the emission savings from wind power.The current power system is heavily reliant on independently acting but state-owned energy companies optimizing their part of the system, and this is partly incompatible with building a robust system supportingrenewable energy technologies. Hence, strategic, top-down co-ordination and incentives to improve the overall electricity infrastructure is recommended.Keywords: Wind power, China, Power grids, Back-up systems1. IntroductionChina’s wind energy industry has exper ienced a rapid growth over the last decade. Since the promulgation of the first Renewable Energy Law in 2006, the cumulative installed capacity of wind energy amounted to 44.7 GW by the end of 2010 [1]. The newly installed capacity in 2010 reached 18.9 GW which accounted for about 49.5% of new windmills globally. The wind energy potential in China is considerable, though with differing estimates from different sources. According to He et al. [2], the exploitable wind energy potential is 600–1000 GW onshore and 100–200 GW offshore. Without considering the limitations of wind energy such as variable power outputs and seasonal variations, McElroy et al. [3] concluded that if the Chinese government commits to an aggressive low carbon energy future, wind energy is capable of generating 6.96 million GWh of electricity by 2030, which is sufficient to satisfy China’s electricity demand in 2030.The existing literature of wind energy development in China focuses on several discussion themes. The majority of the studies emphasize the importance of government policy on the promotion of wind energyindustry in China [4], [5], [6], [7]. For instance, Lema and Ruby [8] compared the growth of wind generation capacity between 1986 and 2006, and addressed the importance of a coordinated government policy and corresponding incentives. Several studies assessed other issues such as the current status of wind energy development in China [9]; the potential of wind power [10]; the significance of wind turbine manufacturing [11]; wind resource assessment [5]; the application of small-scale wind power in rural areas [12]; clean development mechanism in the promotion of wind energy in China [4], social, economic and technical performance of wind turbines [13] etc.There are few studies which assess the challenge of grid infrastructure in the integration of wind power. For instance, Wang [14] studied grid investment, grid security, long-distance transmission and the difficulties of wind power integration at present. Liao et al. [15] criticised the inadequacy of transmission lines in the wind energy development. However, we believe that there is a need to further investigate these issues since they are critical to the development of wind power in China. Furthermore, wind power is not a stand-alone energy source; it needs to be complemented by other energy sources when wind does not blow. Although the viability and feasibility of the combination of wind power with other power generation technologies have been discussed widely in other countries, none of the papers reviewed thesituation in the Chinese context. In this paper, we discuss and clarify two major issues in light of the Chinese wind energy distribution process: 1) the capability of the grid infrastructure to absorb and transmit large amounts of wind powered electricity, especially when these wind farms are built in remote areas; 2) the choices and viability of the backup systems to cope with the fluctuations of wind electricity output.2. Is the existing power grid infrastructure sufficient?Wind power has to be generated at specific locations with sufficient wind speed and other favourable conditions. In China, most of the wind energy potential is located in remote areas with sparse populations and less developed economies. It means that less wind powered electricity would be consumed close to the source. A large amount of electricity has to be transmitted between supply and demand centres leading to several problems associated with the integration with the national power grid system, including grid investment, grid safety and grid interconnection.2.1. Power grid investmentAlthough the two state grid companies-(SGCC) State Grid Corporation of China and (CSG) China Southern Grid - have invested heavily in grid construction, China’s powe r grid is still insufficient to cope with increasing demand. For example, some coal-fired plants in Jiangsu, which is one of the largest electricity consumers in China, had to drop the load ratio to 60 percent against the international standard of 80percent due to the limited transmission capacity [16]. This situation is a result of an imbalanced investment between power grid construction and power generation capacity. For example, during the Eighth Five-Year Plan, Ninth Five-Year Plan and Tenth Five-Year Plan,1 power grid investments accounted for 13.7%, 37.3% and 30% of total investment in the electricity sector, respectively. The ratio further increased from 31.1% in 2005 to 45.94% in 2008, the cumulative investment in the power grid is still significantly lower than the investments in power generation [17]. Fig. 1 gives a comparison of the ratios of accumulative investments in power grid and power generation in China, the US, Japan, the UK and France since 1978. In most of these countries, more than half of the electric power investment has been made on grid construction. By contrast, the ratio is less than 40% in China.According to the Articles 14 and 21 of the Chinese Renewable Energy Law, the power grid operators are responsible for the grid connection of renewable energy projects. Subsidies are given subject to the length of the grid extension with standard rates. However, Mo [18] found that the subsidies were only sufficient to compensate for capital investment and corresponding interest but excluding operational and maintenance costs.Again, similar to grid connection, grid reinforcement requires significant amounts of capital investment. The Three Gorges power planthas provided an example of large-scale and long-distance electricity transmission in China. Similar to wind power, hydropower is usually situated in less developed areas. As a result, electricity transmission lines are necessary to deliver the electricity to the demand centres where the majority are located; these are the eastern coastal areas and the southern part of China. According to SGCC [19], the grid reinforcement investment of the Three Gorges power plants amounted to 34.4 billion yuan (about 5 billion US dollars). This could be a lot higher in the case of wind power due to a number of reasons. First, the total generating capacity of Three Gorges project is approximately 18.2 GW at this moment and will reach 22.4 GW when fully operating [20], whilst the total generating capacity of the massive wind farms amount to over 100 GW. Hence, more transmission capacities are absolutely necessary. Second, the Three Gorges hydropower plant is located in central China. A number of transmission paths are available, such as the 500 kV DC transmission lines to Shanghai (with a length of 1100 km), Guangzhou (located in Guangdong province, with a length of 1000 km) and Changzhou (located in Jiangsu province, with a length of 1000 km) with a transmission capacity of 3 GW each and the 500 kV AC transmission lines to central China with transmission capacity of 12 GW. By contrast, the majority of wind farm bases, which are located in the northern part of China, are far away from the load centres. For example, Jiuquan locatedin Gansu has a planned generation capacity of 20 GW. The distances from Jiuquan to the demand centres of the Central China grid and the Eastern China grid are 1500 km and 2500 km, respectively. For Xinjiang, the distances are even longer at 2500 km and 4000 km, respectively. As a result, longer transmission lines are required. Fig. 2 depicts the demand centres and wind farms in detail.2.2. Grid safetyThe second problem is related to grid safety. The large-scale penetration of wind electricity leads to voltage instability, flickers and voltage asymmetry which are likely to cause severe damage to the stability of the power grid [21]. For example, voltage stability is a key issue in the grid impact studies of wind power integration. During the continuous operation of wind turbines, a large amount of reactive power is absorbed, which lead to voltage stability deterioration [22]. Furthermore, the significant changes in power supply from wind might damage the power quality [23]. Hence, additional regulation capacity would be needed. However, in a power system with the majority of its power from base load provider, the requirements cannot be met easily [24]. In addition, the possible expansion of existing transmission lines would be necessary since integration of large-scale wind would cause congestion and other grid safety problems in the existing transmission system. For example, Holttinen [23] summarized the majorimpacts of wind power integration on the power grid at the temporal level (the impacts of power outputs at second, minute to year level on the power grid operation) and the spatial level (the impact on local, regional and national power grid). Besides the impacts mentioned above, the authors highlight other impacts such as distribution efficiency, voltage management and adequacy of power on the integration of wind power [23].One of the grid safety problems caused by wind power is reported by the (SERC) State Electricity Regulatory Commission [25]. In February and April of 2011, three large-scale wind power drop-off accidents in Gansu (twice) and Hebei caused power losses of 840.43 MW, 1006.223 MW and 854 MW, respectively, which accounted for 54.4%, 54.17% and 48.5% of the total wind powered outputs. The massive shutdown of wind turbines resulted in serious operational difficulties as frequency dropped to 49.854 Hz, 49.815 Hz and 49.95 Hz in the corresponding regional power grids.The Chinese Renewable Energy Law requires the power grid operators to coordinate the integration of windmills and accept all of the wind powered electricity. However, the power grid companies have been reluctant to do so due to the above mentioned problems as well as technical and economic reasons. For instance, more than one third of the wind turbines in China, amounting to 4 GW capacity, were not connectedto the power grid by the end of 2008 [17]. Given that the national grid in China is exclusively controlled by the power companies –SGCC and CSG - the willingness of these companies to integrate wind energy into the electricity generation systems is critical.2.3. The interconnection of provincial and regional power gridsThe interconnection of trans-regional power grids started at the end of 1980s. A (HVDC) high voltage direct current transmission line was established to link the Gezhouba2 dam with Shanghai which signifies the beginning of regional power grids interconnection. In 2001, two regional power grids, the North China Power Grid and Northeast China Power Grid were interconnected. This was followed by the interconnection of the Central China Power Grid and the North China Power Grid in 2003. In 2005, two other interconnection agreements were made between the South China Power Grid with North, Northeast and Central China Power Grid, and the Northwest China Power Grid and the Central China Power Grid. Finally, in 2009, the interconnection of Central China Power Grid and the East China Power Grid was made. In today’s China, the Chinese power transmission systems are composed of 330 kV and 500 kV transmission lines as the backbone and six interconnected regional power grids and one Tibet power grid [26].It seems that the interconnectivity of regional power grids would help the delivery of wind powered outputs from wind-rich regions todemand centres. However, administrative and technical barriers still exist. First, the interconnectivity among regions is always considered as a backup to contingencies, and could not support the large-scale, long-distance electricity transmission [27]. In addition, the construction of transmission systems is far behind the expansion of wind power. The delivery of large amounts of wind power would be difficult due to limited transmission capacity. Furthermore, the quantity of inter-regional electricity transmission is fixed [27]. Additional wind power in the inter-regional transmission might have to go through complex administrative procedures and may result in profit reductions of conventional power plants.3. Are the backup systems geographically available and technically feasible?Power system operators maintain the security of power supply by holding power reserve capacities in operation. Although terminologies used in the classification of power reserves vary among countries [28], power reserves are always used to keep the production and generation in balance under a range of circumstances, including power plant outages, uncertain variations in load and fluctuations in power generations (such as wind) [29]. As wind speed varies on all time scales (e.g. from seconds to minutes and from months to years), the integration of fluctuating wind power generation induces additional system balancing requirements onthe operational timescale [29].A number of studies have examined the approaches to stabilize the electricity output from wind power plants. For example, Belanger and Gagnon [30] conducted a study on the compensation of wind power fluctuations by using hydropower in Canada. Nema et al. [31] discussed the application of wind combined solar PV power generation systems and concluded that the hybrid energy system was a viable alternative to current power supply systems in remote areas. In China, He et al. [2]investigated the choices of combined power generation systems. The combinations of wind-hydro, wind-diesel, wind-solar and wind-gas power were evaluated respectively. They found that, for instance, the wind-diesel hybrid systems were used at remote areas and isolated islands. This is because the wind-diesel hybrid systems have lower generation efficiency and higher generation costs compared to other generation systems. Currently, the wind-solar hybrid systems are not economically viable for large-scale application; thus, these systems have either been used at remote areas with limited electricity demand (e.g. Gansu Subei and Qinghai Tiansuo) or for lighting in some coastal cities [2]. Liu et al. [32] adopted the EnergyPLAN model to investigate the maximum wind power penetration level in the Chinese power system. The authors derived a conclusion that approximately 26% of national power demand could be supplied by wind power by the end of 2007. However, theauthors fail to explain the provision of power reserves at different time scales due to wind power integration.Because of the smoothing effects of dispersing wind turbines at different locations (as exemplified by Drake and Hubacek [33] for the U.K., Roques [34] for the E.U. and Kempton et al. [35] for the U.S.), the integration of wind power has a very small impact on the primary reserves which are available from seconds to minutes [36]. However, the increased reserve requirements are considerable on secondary reserves (available within 10–15 min) which mainly consist of hydropower plants and gas turbine power plants [29]. Besides, the long-term reserves, which are used to restore secondary reserves after a major power deficit, will be in operation to keep power production and consumption in balance for a longer timescale (from several minutes to several hours). In the following subsection, we examine the availability of power plants providing secondary and long-term reserves and investigate the viability of energy storage system in China.中文中国的风力发电–梦想还是现实？胡巴切克摘要经过近几年风力发电能力的巨大增长，中国现在拥有44.7吉瓦的风力发电。
风力发电 英文作文
风力发电英文作文英文：Wind power is a type of renewable energy that has been gaining popularity in recent years. It involves harnessing the power of wind to generate electricity. I think wind power is a great alternative to traditional forms of energy like oil and coal. Not only is it clean and sustainable, but it also has the potential to be very cost-effective.One of the benefits of wind power is that it doesn't produce any greenhouse gas emissions. This means that it doesn't contribute to climate change like fossil fuels do. Additionally, wind power is renewable, meaning that itwon't run out like oil and coal will. This makes it a much more sustainable option for the future.Another advantage of wind power is that it can be very cost-effective. While the initial investment in wind turbines can be expensive, the cost of generatingelectricity from wind power is much lower than with fossil fuels. This is because the fuel (wind) is free, and there are no ongoing costs for mining or transporting fuel.Of course, there are also some challenges associated with wind power. One of the biggest is that wind power is intermittent, meaning that it can't be relied on to generate electricity all the time. This is because wind speeds can vary greatly depending on the weather. However, this can be mitigated by using a combination of different renewable energy sources, like wind and solar power.Overall, I think wind power is a great alternative to traditional forms of energy. It's clean, sustainable, and has the potential to be very cost-effective. While there are some challenges to overcome, I believe that wind power will play an important role in our transition to a more sustainable future.中文：风力发电是一种近年来越来越受欢迎的可再生能源类型。
关于风能的英文文章
关于风能的英文文章1.Wind energy is a clean and renewable source of energy derived from solar radiation and temperature differences between the surface of the Earth and the atmosphere. It is abundant in many parts of the world, particularly in open areas both on land and at sea. With technological advancements and increased demand for renewable energy sources, wind energy has become an important source of electricity.Wind energy generation converts wind energy into electricity. Wind farms typically consist of a series of large wind turbines, known as turbines or windmills. When the wind blows through these turbines, they rotate and drive generators to produce electricity.Wind energy generation has many advantages. Firstly, it is renewable, meaning it does not deplete natural resources. Secondly, wind energy generation does not emit greenhouse gases and other harmful substances, making it environmentally friendly. In addition, wind energy generation can reduce dependence on fossil fuels, thereby reducing dependence on imported energy and enhancing energy security.However, there are also some challenges and limitations to wind energy generation. Firstly, wind speed is unstable, so the power output of a wind farm is also unstable. In addition, the construction and maintenance of wind farms require significant capital investment and expertise. Furthermore, some people argue that wind energy generation may pose a threat to birds and other animals.Despite these challenges, with ongoing technological advancements and increased demand for renewable energy sources, the role of wind energy generation in global energy supply is becoming increasingly important. In the future, with the development of more efficient and reliable wind energy technologies and advanced grid technologies, the prospects for wind energy generation will become even more optimistic.风能是一种清洁、可再生的能源，它来源于太阳辐射和地球表面的温差。
外文翻译--小型风力发电机入门
外文原文Primer on Small Wind TurbinesA Little HistoryThe wind has been an important source of energy in the U.S. for a long time. The mechanical windmill was one of the two "high-technology" inventions (the other was barbed wire) of the late 1800's that allowed us to develop much of our western frontier. Over 8 million mechanical windmills have been installed in the US since the 1860's and some of these units have been in operation for more than a hundred years. Back in the 1920's and 1930's, before the REA began subsidizing rural electric coops and electric lines, farm families throughout the Midwest used 200-3,000 watt wind generators to power lights, radios, and kitchen appliances.In the late 1970's and early 1980's intense interest was once again focused on wind energy as a possible solution to the energy crisis. As homeowners and farmers looked to various electricity producing renewable energy alternatives, small wind turbines emerged as the most cost effective technology capable of reducing their utility bills. Tax credits and favorable federal regulations (PURPA) made it possible for over 4,500 small, 1-25 kW, utility-intertied wind systems to be installed at individual homes between 1976-1985. Another 1,000 systems were installed in various remote applications during the same period. Small wind turbines were installed in all fifty States. None of the small wind turbine companies, however, were owned by large companies committed to long term market development, so when the federal tax credits expired in late 1985, and oil prices dropped to $10 a barrel two months later, most of the small wind turbine industry once again disappeared. The companies that survived this "market adjustment" and are producing small wind turbines today are those whose machines were the most reliable and whose reputations were the best.The Cost FactorPhotovoltaics is an attractive technology in many ways, but cost is not one of them. Small wind turbines can be an attractive alternative, or addition, to those people needing more than 100-200 watts of power for their home, business, or remote facility. Unlike PV's, which stay at basically the same cost per watt independent of array size, wind turbines get less expensive with increasing system size. At the 50 watt size level, for example, a small wind turbine would cost about $8.00/watt compared to approximately$6.00/watt for a PV module. This is why, all things being equal, PV is lessexpensive for very small loads. As the system size gets larger, however, this "rule-of-thumb" reverses itself. At 300 watts the wind turbine costs are down to $2.50/watt ($1.50/watt in the case of the Southwest Windpower Air 403), while the PV costs are still at $6.00/watt. For a 1,500 watt wind system the cost is down to $2.00/watt and at 10,000 watts the cost of a wind generator (excluding electronics) is down to $1.50/watt. The cost of regulators and controls is essentially the same for PV and wind. Somewhat surprisingly, the cost of towers for the wind turbines is about the same as the cost of equivalent PV racks and trackers. The cost of wiring is usually higher for PV systems because of the large number of connections.For homeowners connected to the utility grid, small wind turbines are usually the best "next step" after all the conservation and efficiency improvements have been made. A typical home consumes between 800-2,000 kWh of electricity per month and a 4-10 kW wind turbine or PV system is about the right size to meet this demand. At this size wind turbines are much less expensive.ReliabilityIn the past reliability was the "Achilles Heel" of small wind turbine products. Small turbines designed in the late 1970's had a well deserved reputation for not being very reliable. Today's products, however, are technically advanced over these earlier units and they are substantially more reliable. Small turbines are now available that can operate 5 years or more, even at harsh sites, without need for maintenance or inspections and 5-year warranties are available. The reliability and cost of operation of these units is equal to that of photovoltaic systems.Wind EnergyWind energy is a form of solar energy produced by uneven heating of the Earth's surface. Wind resources are best along coastlines, on hills, and in the northern states, but usable wind resources can be found in most areas. As a power source wind energy is less predictable than solar energy, but it is also typically available for more hours in a given day. Wind resources are influenced by terrain and other factors that make it much more site specific than solar energy. In hilly terrain, for example, you and your neighbor are likely to have the exact same solar resource. But you could have a much better wind resource than your neighbor because your property is on top of the hill or it has a better exposure to the prevailing wind direction. Conversely, if your property is in a gully or on the leeward side of the hill,your wind resource could be substantially lower. In this regard, wind energy must be considered more carefully than solar energy.Wind energy follows seasonal patterns that provide the best performance in the winter months and the lowest performance in the summer months. This is just the opposite of solar energy. For this reason wind and solar systems work well together in hybrid systems. These hybrid systems provide a more consistent year-round output than either wind-only or PV-only systems. One of the most active market segments for small wind turbine manufacturers is PV-only system owners who are expanding their system with wind energy.Wind TurbinesMost wind turbines are horizontal-axis propeller type systems. Vertical-axis systems, such as the eggbeater like Darrieus and S-rotor type Savonius type systems, have proven to be more expensive. A horizontal-axis wind turbine consists of a rotor, a generator, a mainframe, and, usually, a tail. The rotor captures the kinetic energy of the wind and converts it into rotary motion to drive the generator. The rotor usually consists of two or three blades. A three blade unit can be a little more efficient and will run smoother than a two blade rotor, but they also cost more. The blades are usually made from either wood or fiberglass because these materials have the needed combination of strength and flexibility (and they don't interfere with television signals!).The generator is usually specifically designed for the wind turbine. Permanent magnet alternators are popular because they eliminate the need for field windings. A low speed direct drive generator is an important feature because systems that use gearboxes or belts have generally not been reliable. The mainframe is the structural backbone of the wind turbine and it includes the "slip-rings" that connect the rotating (as it points itself into changing wind directions) wind turbine and the fixed tower wiring. The tail aligns the rotor into the wind and can be a part of the over speed protection.A wind turbine is a deceptively difficult product to develop and many of the early units were not very reliable. A PV module is inherently reliable because it has no moving parts and, in general, one PV module is as reliable as the next. A wind turbine, on the other hand, must have moving parts and the reliability of a specific machine is determined by the level of skill used in its engineering and design. In other words, there can be a big difference in reliability, ruggedness, and life expectancy from one brandto the next. This is a lesson that often seems to escape dealers and customers who are used to working with solar modules.TowersA wind turbine must have a clear shot at the wind to perform efficiently. Turbulence, which both reduces performance and "works" the turbine harder than smooth air, is highest close to the ground and diminishes with height. Also, wind speed increases with height above the ground. As a general rule of thumb, you should install a wind turbine on a tower such that it is at least 30 ft above any obstacles within 300 ft. Smaller turbines typically go on shorter towers than larger turbines. A 250 watt turbine is often, for example, installed on a 30-50 ft tower, while a 10 kW turbine will usually need a tower of 80-120 ft. We do not recommend mounting wind turbines to small buildings that people live in because of the inherent problems of turbulence, noise, and vibration.The least expensive tower type is the guyed-lattice tower, such as those commonly used for ham radio antennas. Smaller guyed towers are sometimes constructed with tubular sections or pipe. Self-supporting towers, either lattice or tubular in construction, take up less room and are more attractive but they are also more expensive. Telephone poles can be used for smaller wind turbines. Towers, particularly guyed towers, can be hinged at their base and suitably equipped to allow them to be tilted up or down using a winch or vehicle. This allows all work to be done at ground level. Some towers and turbines can be easily erected by the purchaser, while others are best left to trained professionals. Anti-fall devices, consisting of a wire with a latching runner, are available and are highly recommended for any tower that will be climbed. Aluminum towers should be avoided because they are prone to developing cracks. Towers are usually offered by wind turbine manufacturers and purchasing one from them is the best way to ensure proper compatibility.Remote Systems EquipmentThe balance-of-systems equipment used with a small wind turbine in a remote application is essentially the same as used with a PV system. Most wind turbines designed for battery charging come with a regulator to prevent overcharge. The regulator is specifically designed to work with that particular turbine. PV regulators are generally not suitable for use with a small wind turbine because they are not designed to handle the voltage and current variations found with turbines. The output from the regulator istypically tied into a DC source center, which also serves as the connection point for other DC sources, loads and the batteries. For a hybrid system the PV and wind systems are connected to the DC source center through separate regulators, but no special controls are generally required. For small wind turbines a general rule-of-thumb is that the AH capacity of the battery bank should be at least six times the maximum renewables charging current, including any PV elements. The wind industry has had good experience using battery banks that are smaller than those typically recommended for PV applications.Being Your Own Utility CompanyThe federal PURPA regulations passed in 1978 allow you to interconnect a suitable renewable energy powered generator to your house or business to reduce your consumption of utility supplied electricity. This same law requires utilities to purchase any excess electricity production at a price (avoided cost) usually below the retail cost of electricity. In about a half-dozen states with "net energy billing options" small systems are allowed to run the meter backwards, so they get the full retail rate for excess production. Because of the high overhead costs to the utilities for keeping a few special hand-processed customer accounts, net energy billing is actually less expensive for them. These systems do not use batteries. The output of the wind turbine is made compatible with utility power using either a line-commutated inverter or an induction generator. The output is then connected to the household breaker panel on a dedicated breaker, just like a large appliance. When the wind turbine is not operating, or it is not putting out as much electricity as the house needs, the additional electricity needed is supplied by the utility. Likewise, if the turbine puts out more power than the house needs, the excess is instantaneously "sold" to the utility. In effect, the utility acts as a very big battery bank and the utility "sees" the wind turbine as a negative load. After over 200 million hours of interconnected operation we now know that small utility-interconnected wind turbines are safe, do not interfere with either utility or customer equipment, and do not need any special safety equipment to operate successfully.Hundreds of homeowners around the country who installed 4-12 kW wind turbines during the go-go tax credit days in the early 1980's now have everything paid for and enjoy monthly electrical bills of $8-30, while their neighbors have bills in the range of $100-200 per month. The problem, of course, is that these tax credits are long gone and without them most homeowners will find the cost of a suitable wind generator prohibitively expensive. A 10 kW turbine (the most common size for homes), for example,will typically cost $28,000-35,000 installed. For those paying 12cents/kilowatt-hour or more for electricity in an area with an average wind speed of 10 mph or more (DOE Class 2), and with an acre or more of property (the turbines are big), a residential wind turbine is certainly worth considering. Payback periods will generally fall in the range of 8-16 years and some wind turbines are designed to last thirty years or more.PerformanceThe rated power for a wind turbine is not a good basis for comparing one product to the next. This is because manufacturers are free to pick the wind speed at which they rate their turbines. If the rated wind speeds are not the same then comparing the two products is very misleading. Fortunately, the American Wind Energy Association has adopted a standard method of rating energy production performance. Manufacturers who follow the AWEA standard will give information on the Annual Energy Output (AEO) at various annual average wind speeds. These AEO figures are like the EPA Estimated Gas Mileage for your car, they allow you to compare products fairly, but they don't tell you just what your actual performance will be ("Your Performance May Vary").Wind resource maps for the US have been compiled by the Department of Energy. These maps show the resource by "Power Classes" that mean the average wind speed will probably be within a certain band. The higher the Power Class the better the resource. We say probably because of the terrain effects mentioned earlier. On open terrain the DOE maps are quite good, but in hilly or mountainous terrain they must be used with great caution. The wind resource is defined for a standard wind sensor height of 33 ft (10 m), so you must correct the average wind speed for wind tower heights above this height before using the AEO information supplied by the manufacturer. Wind turbine performance is also usually derated for altitude, just like an airplane, and for turbulence. Wind turbine manufacturers can usually providecomputer-aided performance predictions for their turbines at virtually any site.As a rule of thumb wind energy should be considered if your average wind speed is above 8 mph (most, but not all, Class 1 and all other Classes) for a remote application and 10 mph (Class 2 or better) for a utility-interited application. If you live in an area that is not too hilly then the DOE wind resource map can be used to fairly accurately calculate the expected performance of a wind turbine at your site. In complex terrain a judgment on the site's exposure must be made to adjust the average wind speed used for this calculation. In most situations it is not necessary to monitor thewind speed with a recording anemometer prior to installing a small wind turbine. But in some situations it is worth spending $300-1,000 and waiting a year to perform a wind survey. Manufacturers and equipment dealers can help sort out these questions.How Wind Turbines are UsedInstalling a wind turbine is a bit more involved than installing solar panels, but they are still relatively easy to incorporate into your alternative energy system. The turbine needs to be mounted in an area free from obstructions to wind flow (nearby buildings, trees, etc.).Some smaller turbines can be mounted to the rooftop of your house, but vibrations from the turbine may be transferred to the frame of the building. Rooftop turbine mounts often come with rubber vibration dampers to minimize this problem. As a general rule however, the higher in the air you can get your wind turbine the more effective it will be, so independent, guyed towers are the recommended mounting system. The wide variety of available tower heights and styles makes it much more likely you will find a mounting kit to suit your needs.When installing the controls and wiring of a wind generator, it is important to understand two fundamental differences between wind turbines and solar panels:Current Rectifiers: Solar panels produce direct current (DC) electricity required by power storage batteries, and can be connected directly to the battery bank without causing harm. Wind generators do not produce DC electricity, so a device called a "rectifier" is used to convert the turbine's output current to DC.Some turbines have a rectifier built in. In most cases though, the rectifier is supplied as a separate component that must be installed between the wind turbine and the battery. Often, the rectifier is combined with a charge controller into one complete wind turbine control unit.Load Diversion:Solar panels are "passive" electricity producers. Even though the sun is shining, they only produce electricity when a charge is needed by the battery. Wind generators are "active" electricity producers. If the wind is blowing, they will produce current whether the battery bank needs the charge or not. In order to prevent damage to the wind turbine, all of the electricity it produces must be "used" in.When the system batteries need charging current, they provide an electrical load to use the wind turbine's electricity. If the batteries are fully charged, the turbine's output must be "diverted" to another electrical load.A load diverting charge controller regulates wind generator output so your batteries receive charging current when they need it, and any excess electricity generated by the wind turbine is diverted to an alternate load when the batteries are fully charged.Some wind turbines have charge control features built-in, diverting their own excess current and allowing it to dissipate as heat through the wind turbine housing. In most turbine systems however, the charge controller is an external unit.中文译文小型风力发电机入门历史在美国相当长的时间里，风能一直是一个重要的能量来源。
风力发电电力系统中英文对照外文翻译文献
中英文对照外文翻译(文档含英文原文和中文翻译)附件1：翻译译文风力发电对电力系统的影响摘要风力发电依赖于气象条件，并逐渐以大型风电场的形式并入电网，给电网带来各种影响。
电网并未专门设计用来接入风电，因此如果要保持现有的电力供应标准，不可避免地需要进行一些相应的调整。
讨论了在风电场并网时遇到的各种问题。
由于风力发电具有大容量、动态和随机的特性，它给电力系统的有功/无功潮流、电压、系统稳定性、电能质量、短路容量、频率和保护等方面带来影响。
针对这些问题提出了相应的解决建议和措施，以及更好利用风力发电。
关键词：风力发电；电力系统；影响；风电场1.引言人们普遍接受，可再生能源发电是未来电力的供应。
由于电力需求快速增长，对以化石燃料为基础的发电是不可持续的。
正相反，风力发电作为一种有前途的可再生能源受到了很多关注。
当由于工业的发展和在世界大部分地区的经济增长而发电的消费需求一直稳步增长时，它有减少排放和降低不可替代的燃料储备消耗的潜力。
当大型风电场（几百兆瓦）是一个主流时，风力发电越来越更受欢迎。
2006年间，世界风能装机容量从2005年的59091兆瓦达到74223兆瓦。
在2006年极大的生长表明，决策者开始重视的风能发展能够带来的好处。
由于到2020年12%的供电来于1250GW的安装风电装机，将节约累积10771000000吨二氧化碳[1]。
大型风电场的电力系统具有很高的容量，动态随机性能，这将会挑战系统的安全性和可靠性。
而提供电力系统清洁能源的同时，风农场也会带来一些对电力系统不利的因素。
风力发电的扩展和风电在电力系统的比重增加，影响将很可能成为风力集成的技术性壁垒。
因此，应该探讨其影响和提出克服这些问题的对策。
2.风力发电发展现状从全球风能委员会（GWEC）的报告中，拥有最高装机容量总数的国家是德国（20621兆瓦），西班牙（11615兆瓦），美国（11603兆瓦），印度（6270兆瓦）和丹麦（3136兆瓦）。
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风力发电外文翻译中英文英文Wind power in China – Dream or reality?HubacekAbstractAfter tremendous growth of wind power generation capacity in recent years, China now has 44.7 GW of wind-derived power. Despite the recent growth rates and promises of a bright future, two important issues - the capability of the grid infrastructure and the availability of backup systems - must be critically discussed and tackled in the medium term.The study shows that only a relatively small share of investment goes towards improving and extending the electricity infrastructure which is a precondition for transmitting clean wind energy to the end users. In addition, the backup systems are either geographically too remote from the potential wind power sites or currently financially infeasible. Finally, the introduction of wind power to the coal-dominated energy production system is not problem-free. Frequent ramp ups and downs of coal-fired plants lead to lower energy efficiency and higher emissions, which are likely to negate some of the emission savings from wind power.The current power system is heavily reliant on independentlyacting but state-owned energy companies optimizing their part of the system, and this is partly incompatible with building a robust system supporting renewable energy technologies. Hence, strategic, top-down co-ordination and incentives to improve the overall electricity infrastructure is recommended.Keywords: Wind power, China, Power grids, Back-up systems1. IntroductionChina 'wsi nd energy industry has experienced a rapid growth over the last decade. Since the promulgation of the first Renewable Energy Law in 2006, the cumulative installed capacity of wind energy amounted to 44.7 GW by the end of 2010 [1]. The newly installed capacity in 2010 reached 18.9 GW which accounted for about 49.5% of new windmills globally. The wind energy potential in China is considerable, though with differing estimates from different sources. According to He et al. [2], the exploitable wind energy potential is 600–1000 GW onshore and 100–200 GW offshore. Without considering the limitations of wind energy such as variable power outputs and seasonal variations, McElroy et al. [3] concluded that if the Chinese government commits to an aggressive low carbon energy future, wind energy is capable of generating 6.96 million GWh of electricity by 2030, which is sufficient to satisfy China ' selectricity demand in 2030.The existing literature of wind energy development in China focuses on several discussion themes. The majority of the studies emphasize the importance of government policy on the promotion of wind energy industry in China [4], [5], [6], [7]. For instance, Lema and Ruby [8] compared the growth of wind generation capacity between 1986 and 2006, and addressed the importance of a coordinated government policy and corresponding incentives. Several studies assessed other issues such as the current status of wind energy development in China [9]; the potential of wind power [10]; the significance of wind turbine manufacturing [11]; wind resource assessment [5]; theapplication of small-scale wind power in rural areas [12]; clean development mechanism in the promotion of wind energy in China [4], social, economic and technical performance of wind turbines [13] etc.There are few studies which assess the challenge of grid infrastructure in the integration of wind power. For instance, Wang [14] studied grid investment, grid security, long-distance transmission and the difficulties of wind power integration at present. Liao et al. [15] criticised the inadequacy of transmission lines in the wind energy development. However, webelieve that there is a need to further investigate these issues since they are critical to the development of wind power in China. Furthermore, wind power is not a stand-alone energy source; it needs to be complemented by other energy sources when wind does not blow. Although the viability and feasibility of the combination of wind power with other power generation technologies have been discussed widely in other countries, none of the papers reviewed the situation in the Chinese context. In this paper, we discuss and clarify two major issues in light of the Chinese wind energy distribution process: 1) the capability of the grid infrastructure to absorb and transmit large amounts of wind powered electricity, especially when these wind farms are built in remote areas; 2) the choices and viability of the backup systems to cope with the fluctuations of wind electricity output.2. Is the existing power grid infrastructure sufficient?Wind power has to be generated at specific locations with sufficient wind speed and other favourable conditions. In China, most of the wind energy potential is located in remote areas with sparse populations and less developed economies. It means that less wind powered electricity would be consumed close to the source. A large amount of electricity has to be transmittedbetween supply and demand centres leading to several problems associated with the integration with the national power grid system, including grid investment, grid safety and grid interconnection.2.1.P ower grid investmentAlthough the two state grid companies-(SGCC) State Grid Corporation of China and (CSG) China Southern Grid - have invested heavily in grid construction, China 'pso wer grid is still insufficient to cope with increasing demand. For example, some coal-fired plants in Jiangsu, which is one of the largest electricity consumers in China, had to drop the load ratio to 60 percent against the international standard of 80 percent due to the limited transmission capacity [16]. This situation is a result of an imbalanced investment between power grid construction and power generation capacity. For example, during the Eighth Five-Year Plan, Ninth Five-Year Plan and Tenth Five-Year Plan,1 power grid investments accounted for 13.7%, 37.3% and 30% of total investment in the electricity sector, respectively. The ratio further increased from 31.1% in 2005 to 45.94% in 2008, the cumulative investment in the power grid is still significantly lower than the investments in power generation [17]. Fig. 1 gives a comparison of the ratios ofaccumulative investments in power grid and power generation in China, the US, Japan, the UK and France since 1978. In most of these countries, more than half of the electric power investment has been made on grid construction. By contrast, the ratio is less than 40% in China.According to the Articles 14 and 21 of the Chinese Renewable Energy Law, the power grid operators are responsible for thegrid connection of renewable energy projects. Subsidies are given subject to the length of the grid extension with standard rates. However, Mo [18] found that the subsidies were only sufficient to compensate for capital investment and corresponding interest but excluding operational and maintenance costs.Again, similar to grid connection, grid reinforcement requires significant amounts of capital investment. The Three Gorges power plant has provided an example of large-scale and long-distance electricity transmission in China. Similar to wind power, hydropower is usually situated in less developed areas. As a result, electricity transmission lines are necessaryt o deliver the electricity to the demand centres where the majority are located; these are the eastern coastal areas and the southern part of China. According to SGCC [19], the gridreinforcement investment of the Three Gorges power plants amounted to 34.4 billion yuan (about 5 billion US dollars). This could be a lot higher in the case of wind power due to a number of reasons. First, the total generating capacity of Three Gorges project is approximately 18.2 GW at this moment and will reach 22.4 GW when fully operating [20], whilst the total generating capacity of the massive wind farms amount to over 100 GW. Hence, more transmission capacities are absolutely necessary. Second, the Three Gorges hydropower plant is located in central China. A number of transmission paths are available, such as the 500 kV DC transmission lines to Shanghai (with a length of 1100 km), Guangzhou (located in Guangdong province, with a length of 1000 km) and Changzhou (located in Jiangsu province, with a length of 1000 km) with a transmission capacity of 3 GW each and the 500 kV AC transmission lines to central China with transmission capacity of 12 GW. By contrast, the majority of wind farm bases, which are located in the northern part of China, are far away from the load centres. For example, Jiuquan located in Gansu has a planned generation capacity of 20 GW. The distances from Jiuquan to the demand centres of the Central China grid and the Eastern China grid are 1500 km and 2500 km, respectively. For Xinjiang, the distances are even longer at 2500 km and 4000 km,respectively. As a result, longer transmission lines are required. Fig. 2 depicts the demand centres and wind farms in detail.2.2.Grid safetyThe second problem is related to grid safety. The large-scale penetration of wind electricity leads to voltage instability, flickers and voltage asymmetry which are likely to cause severe damage to the stability of the power grid [21]. For example, voltage stability is a key issue in the grid impact studies of wind power integration. During the continuous operation of wind turbines, a large amount of reactive power is absorbed, which lead to voltage stability deterioration [22]. Furthermore, the significant changes in power supply from wind might damage the power quality [23]. Hence, additional regulation capacity would be needed. However, in a power system with the majority of its power from base load provider, the requirements cannot be met easily [24]. In addition, the possible expansion of existing transmission lines would be necessary since integration of large-scale wind would cause congestion and other grid safety problems in the existing transmission system. For example, Holttinen [23] summarized the majorimpacts of wind power integration on the power grid at the temporal level (the impacts of power outputs at second, minute to year level on the power grid operation) and the spatial level (the impact on local, regional and national power grid). Besides the impacts mentioned above, the authors highlight other impacts such as distribution efficiency, voltage management and adequacy of power on the integration of wind power [23].One of the grid safety problems caused by wind power is reported by the (SERC) State Electricity Regulatory Commission [25]. In February and April of 2011, three large-scale wind power drop-off accidents in Gansu (twice) and Hebei caused power losses of 840.43 MW, 1006.223 MW and 854 MW, respectively, which accounted for 54.4%, 54.17% and 48.5% of the total wind powered outputs. The massive shutdown of wind turbines resulted in serious operational difficulties as frequency dropped to 49.854 Hz, 49.815 Hz and 49.95 Hz in the corresponding regional power grids.The Chinese Renewable Energy Law requires the power grid operators to coordinate the integration of windmills and accept all of the wind powered electricity. However, the power grid companies have been reluctant to do so due to the above mentioned problems as well as technical and economic reasons. For instance, more than one third of the wind turbines in China, amounting to 4 GW capacity, were not connected to the power grid by the end of 2008 [17]. Given that the national grid in China is exclusively controlled by the power companies – SGCC and CSG - the willingness ofthese companies to integrate wind energy into the electricity generation systems is critical.2.3.T he interconnection of provincial and regional power gridsThe interconnection of trans-regional power grids started at the end of 1980s. A (HVDC) high voltage direct current transmission line was established to link the Gezhouba2 dam with Shanghai which signifies the beginning of regional power grids interconnection. In 2001, two regional power grids, the North China Power Grid and Northeast China Power Grid were interconnected. This was followed by the interconnection of the Central China Power Grid and the North China Power Grid in 2003. In 2005, two other interconnection agreements were made between the South China Power Grid with North, Northeast and Central China Power Grid, and the Northwest China Power Grid and the Central China Power Grid. Finally, in 2009, the interconnection of Central China Power Grid and the East China Power Grid was made. In today ' s China, the Chinesepower transmission systems are composed of 330 kV and 500 kV transmission lines as the backbone and six interconnected regional power grids and one Tibet power grid [26].It seems that the interconnectivity of regional power grids would help the delivery of wind powered outputs from wind-rich regions todemand centres. However, administrative and technical barriers stillexist. First, the interconnectivity among regions is always considered as a backup to contingencies, and could not support the large-scale, long-distance electricity transmission [27]. In addition, the construction of transmission systems is far behind the expansion of wind power. The delivery of large amounts of wind power would be difficult due to limited transmission capacity. Furthermore, the quantity of inter-regional electricity transmission is fixed [27]. Additional wind power in theinter-regional transmission might have to go through complexadministrative procedures and may result in profit reductions of conventional power plants.3. Are the backup systems geographically available and technically feasible?Power system operators maintain the security of power supply by holding power reserve capacities in operation. Although terminologies used in the classification of power reserves vary among countries [28], power reserves are always used to keep the production and generation in balance under a range of circumstances, including power plant outages, uncertain variations in load and fluctuations in power generations (such as wind) [29]. As wind speed varies on all time scales (e.g. from seconds to minutes and from months to years), the integration of fluctuating wind power generation induces additional system balancing requirements on the operational timescale [29].A number of studies have examined the approaches to stabilize the electricity output from wind power plants. For example, Belanger and Gagnon [30] conducted a study on the compensation of wind power fluctuations by using hydropower in Canada. Nema et al. [31] discussed the application of wind combined solar PV power generation systems and concluded that the hybrid energy system was a viable alternative to current power supply systems in remote areas. In China, He et al. [2]investigated the choices of combined power generation systems. The combinations of wind-hydro, wind-diesel, wind-solar and wind-gas power were evaluated respectively. They found that, for instance, the wind-diesel hybrid systems were used at remote areas and isolated islands. This is because the wind-diesel hybrid systems have lower generation efficiency and higher generation costs compared to other generation systems. Currently, the wind-solar hybrid systems are not economically viable for large-scale application; thus, these systems have either been used at remote areas with limited electricity demand (e.g. Gansu Subei and Qinghai Tiansuo) or for lighting in some coastal cities [2]. Liu et al. [32] adopted the EnergyPLAN model to investigate the maximum wind power penetration level in the Chinese power system. The authors derived a conclusion that approximately 26% of national power demand could be supplied by wind power by the end of 2007. However, theauthors fail to explain the provision of power reserves at different time scales due to wind power integration.Because of the smoothing effects of dispersing wind turbines at different locations (as exemplified by Drake and Hubacek [33] for theU.K., Roques [34] for the E.U. and Kempton et al. [35] for the U.S.), the integration of wind power has a very small impact on the primary reserves which are available from seconds to minutes [36]. However, the increased reserve requirements are considerable on secondary reserves (available within 10 –15 min) which mainly consist of hydropower plants and gas turbine power plants [29]. Besides, the long-term reserves, which are used to restore secondary reserves after a major power deficit, will be in operation to keep power production and consumption in balance for a longer timescale (from several minutes to several hours). In the following subsection, we examine the availability of power plants providing secondary and long-term reserves and investigate the viability of energy storage system in China.中文中国的风力发电–梦想还是现实？胡巴切克摘要经过近几年风力发电能力的巨大增长，中国现在拥有 44.7 吉瓦的风力发电。