With the continuous improvement of permanent magnet(PM)wind generators'capacity and power density,the design of reasonable and efficient cooling structures has become a focus.This paper proposes a fully enclosed s...With the continuous improvement of permanent magnet(PM)wind generators'capacity and power density,the design of reasonable and efficient cooling structures has become a focus.This paper proposes a fully enclosed self-circulating hydrogen cooling structure for a originally forced-air-cooled direct-drive PM wind generator.The proposed hydrogen cooling system uses the rotor panel supports that hold the rotor core as the radial blades,and the hydrogen flow is driven by the rotating plates to flow through the axial and radial vents to realize the efficient cooling of the generator.According to the structural parameters of the cooling system,the Taguchi method is used to decouple the structural variables.The influence of the size of each cooling structure on the heat dissipation characteristic is analyzed,and the appropriate cooling structure scheme is determined.展开更多
The electromagnetic characteristics and iron loss of a high-temperature superconductor wind generator(HWG)equipped with an overlapped field coil arrangement(OFCA)are studied by comparing with the one equipped with the...The electromagnetic characteristics and iron loss of a high-temperature superconductor wind generator(HWG)equipped with an overlapped field coil arrangement(OFCA)are studied by comparing with the one equipped with the conventional field coil arrangement(CFCA).Through a quantitative analysis,it was found that HWG with OFCA exhibits better electromagnetic characteristics than HWG with CFCA and can reduce the iron loss by eliminating the magnetic flux sag caused by the adjacent field coil sides with the same current flow direction.In addition,the OFCA topology can further reduce the volume of the wind generator.展开更多
This paper investigates the function of doubly-fed asynchronous machine(DASM)with emphasis placed on its ability to the stabilization of the power system including wind generators.P(active power)and Q(reactive power)c...This paper investigates the function of doubly-fed asynchronous machine(DASM)with emphasis placed on its ability to the stabilization of the power system including wind generators.P(active power)and Q(reactive power)compensation from DASM can be regulated independently through secondary-excitation controlling.Simulation results by power system computer aided design(PSCAD)show that DASM can restore the wind-generator system to a normal operating condition rapidly even following severe transmission-line failures.Comparison studies have also been performed between wind turbine pitch control and proposed method.展开更多
With the rapid increase of wind farms,the grid code needs to be improved to meet the requirement of wind farms and enhance grid stability.Doubly-fed induction generators are largely used in wind turbines,but they are ...With the rapid increase of wind farms,the grid code needs to be improved to meet the requirement of wind farms and enhance grid stability.Doubly-fed induction generators are largely used in wind turbines,but they are very sensitive to grid disturbances.The voltage swell can be caused by switching on capacitor banks or switching off large loads,which may result in the reversal of the power flow in the grid convertor;the current may flow from the grid into the DC link,which may step up DC voltage,and result in large faults of rotor currents and instantaneous power oscillation.The grid reactive compensation devices can not have the automatic swithing function after the low voltage fault,which will result in local reactive power surplus,so some wind power generators will retreat from the grid under high voltage protection.展开更多
The wind energy generation,utilization and its grid penetration in electrical grid are increasing world-wide.The wind generated power is always fluctuating due to its time varying nature and causing stability problem....The wind energy generation,utilization and its grid penetration in electrical grid are increasing world-wide.The wind generated power is always fluctuating due to its time varying nature and causing stability problem.This weak interconnection of wind generating source in the electrical network affects the power quality and reliability.The localized energy storages shall compensate the fluctuating power and support to strengthen the wind generator in the power system.In this paper,it is proposed to control the voltage source inverter （VSI） in current control mode with energy storage,that is,batteries across the dc bus.The generated wind power can be extracted under varying wind speed and stored in the batteries.This energy storage maintains the stiff voltage across the dc bus of the voltage source inverter.The proposed scheme enhances the stability and reliability of the power system and maintains unity power factor.It can also be operated in stand-alone mode in the power system.The power exchange across the wind generation and the load under dynamic situation is feasible while maintaining the power quality norms at the common point of coupling.It strengthens the weak grid in the power system.This control strategy is evaluated on the test system under dynamic condition by using simulation.The results are verified by comparing the performance of controllers.展开更多
In the early development of the wind energy, the majority of the wind turbines have been operated at constant speed. Subsequently, the number of variable-speed wind turbines installed in wind farms has increased. In t...In the early development of the wind energy, the majority of the wind turbines have been operated at constant speed. Subsequently, the number of variable-speed wind turbines installed in wind farms has increased. In this paper, a comparative performance of fixed and variable speed wind generators with Pitch angle control has been presented. The first is based on a squirrel cage Induction Generator （IG） of 315 kW rated power, connected directly to the grid. The second incorporated a Permanent Magnet Synchronous Generator （PMSG） of 750 kW rated power. The performances of each studied wind generator are evaluated by simulation works and variable speed operation is highlighted as preferred mode of operation.展开更多
This paper reviews the status and progress of the investigation on power system small-signal angular stability as affected by grid-connected variable speed wind generators(VSWGs).The review is carried out on the basis...This paper reviews the status and progress of the investigation on power system small-signal angular stability as affected by grid-connected variable speed wind generators(VSWGs).The review is carried out on the basis of a survey of recently published representative papers.Strategies of the investigation made in those selected papers are classified into two groups:1)VSWGs displacing synchronous generators(SGs);2)VSWGs simply being added in a power system.The diversification of the results of the investigation is highlighted in the survey.Careful analysis on two strategies of the investigation is conducted in this paper.It is revealed that in the strategy of VSWGs displacing SGs,there are two factors which could affect power system small-signal angular stability differently:1)Withdrawing the SGs’dynamics;2)adding the VSWGs’dynamics.In the strategy of adding VSWGs in the power system,there are also two affecting factors:1)Change of load flow brought about by the VSWGs;2)dynamic interactions with the SGs introduced by the VSWGs.Hence diversified results of the investigation obtained so far are not only due to the dependence of the investigation on sample power systems used,but also caused by the mixture of different affecting factors.This paper is concluded with a summary of key issues of the investigation for future work.展开更多
According to the increasing requirement of the wind energy utilization and the dynamic stability in the variable speed variable pitch wind power generation system, a linear parameter varying （LPV） system model is es...According to the increasing requirement of the wind energy utilization and the dynamic stability in the variable speed variable pitch wind power generation system, a linear parameter varying （LPV） system model is established and a new adaptive robust guaranteed cost controller （AGCC） is proposed in this paper. First, the uncertain parameters of the system are estimated by using the adaptive method, then the estimated uncertain parameters and robust guaranteed cost control method are used to design a state feedback controller. The controller s feedback gain is obtained by solving a set of linear matrix inequality （LMI） constraints, such that the controller can meet a quadratic performance evaluation criterion. The simulation results show that we can realize the goal of maximum wind energy capture in low wind speed by the optimal torque control and constant power control in high wind speed by variable pitch control with good dynamic characteristics, robustness and the ability of suppressing disturbance.展开更多
Rotor vibration characteristics are first analyzed, which are that the rotor vibration of fundamental frequency will increase due to rotor winding inter-turn short circuit fault, air-gap dynamic eccentricity fault, or...Rotor vibration characteristics are first analyzed, which are that the rotor vibration of fundamental frequency will increase due to rotor winding inter-turn short circuit fault, air-gap dynamic eccentricity fault, or imbalance fault, and the vibration of the second frequency will increase when the air-gap static eccentricity fault occurs. Next, the characteristics of the stator winding parallel branches circulating current are analyzed, which are that the second harmonics circulating current will increase when the rotor winding inter-turn short circuit fault occurs, and the fundamental circulating current will increase when the air-gap eccentricity fault occurs, neither being strongly affected by the imbalance fault. Considering the differences of the rotor vibration and circulating current characteristics caused by different rotor faults, a method of generator vibration fault diagnosis, based on rotor vibration and circulating current characteristics, is developed. Finally, the rotor vibration and circulating current of a type SDF-9 generator is measured in the laboratory to verify the theoretical analysis presented above.展开更多
A distribution grid is generally characterized by a high R/X （resistance/reactance） ratio and it is radial in nature. By design, a distribution grid system is not an active network, and it is normally designed in su...A distribution grid is generally characterized by a high R/X （resistance/reactance） ratio and it is radial in nature. By design, a distribution grid system is not an active network, and it is normally designed in such a way that power flows from transmission system via distribution system to consumers. But in a situation when wind turbines are connected to the distribution grid, the power source will change from one source to two sources, in this case, network is said to be active. This may probably have an impact on the distribution grid to whenever the wind turbine is connected. The best way to know the impact of wind turbine on the distribution grid in question is by carrying out load flow analysis on that system with and without the connection of wind turbines. Two major fundamental calculations： the steady-state voltage variation at the PCC （point of common coupling） and the calculation of short-circuit power of the grid system at the POC （point of connection） are necessary before carrying out the load flow study on the distribution grid. This paper, therefore, considers these pre-load flow calculations that are necessary before carrying out load flow study on the test distribution grid. These calculations are carded out on a test distribution system.展开更多
The control strategy is one of the most important renewable technology,and an increasing number of multi-MW wind turbines are being developed with a variable speed-variable pitch(VS-VP)technology.The main objective of...The control strategy is one of the most important renewable technology,and an increasing number of multi-MW wind turbines are being developed with a variable speed-variable pitch(VS-VP)technology.The main objective of adopting a VS-VP technology is to improve the fast response speed and capture maximum energy.But the power generated by wind turbine changes rapidly because of the continuous fluctuation of wind speed and direction.At the same time,wind energy conversion systems are of high order,time delays and strong nonlinear characteristics because of many uncertain factors.Based on analyzing the all dynamic processes of wind turbine,a kind of layered multi-mode optimal control strategy is presented which is that three control strategies:bang-bang,fuzzy and adaptive proportional integral derivative(PID)are adopted according to different stages and expected performance of wind turbine to capture optimum wind power,compensate the nonlinearity and improve the wind turbine performance at low,rated and high wind speed.展开更多
The optimal torque(OT)method,which is preferred for its simplicity,is widely employed in maximum power point tracking(MPPT)control strategies for wind energy capture in wind turbine generators(WTGs).Based on the OT me...The optimal torque(OT)method,which is preferred for its simplicity,is widely employed in maximum power point tracking(MPPT)control strategies for wind energy capture in wind turbine generators(WTGs).Based on the OT method,the decreased torque gain(DTG)method is developed to improve turbine acceleration through a reduction of the torque gain coefficient.However,the DTG method does not fully align with the acceleration performance required by wind turbines,which subsequently limits improvements in wind energy capture efficiency.To address these concerns,a novel MPPT control strategy is proposed,which introduces redefined torque curve and torque command conceptualized based on a higher-order function relative to rotor speed.Additionally,an adaptive algorithm for the periodic update of the torque command is suggested to better accommodate the variability of turbulent wind speeds,thus aiming to improve the wind energy capture efficiency.The effectiveness of the proposed MPPT control strategy is substantiated through the wind turbine simulator(WTS)-based experiments.展开更多
The impact of large-scale grid-connected renewable power sources, such as wind generators and solar photovoitaic systems, on transient stability of synchronous generators is discussed in this paper. The permanent magn...The impact of large-scale grid-connected renewable power sources, such as wind generators and solar photovoitaic systems, on transient stability of synchronous generators is discussed in this paper. The permanent magnet synchronous generator with variable speed wind turbine is used in the simulation analysis as a wind generator model. The transient stability analysis is performed for IEEE 9-bus system model with high-penetration renewable power sources. The effect of FRT （fault ride-through） capability implemented for each power source on the transient stability is investigated.展开更多
Wind energy is currently a fast-growing interdisciplinary field that encompasses many different branches of engineering and science. Modeling and controlling wind energy systems are difficult and challenging problems....Wind energy is currently a fast-growing interdisciplinary field that encompasses many different branches of engineering and science. Modeling and controlling wind energy systems are difficult and challenging problems. The basic structure of wind turbines and some wind control system methods are briefly reviewed. The need for using advanced theories from fuzzy and intelligent systems in studying wind energy systems is identified and justified. FCMs （fuzzy cognitive maps） are used to model wind energy systems. Simulation studies are performed and obtained results are discussed. A new mathematical approach has been proposed to model dynamical complex systems, the DYFUKN （dynamic fuzzy knowledge networks）. Many open problems in the areas of modeling and controlling wind energy systems are outlined.展开更多
Due to randomness of wind generator＇s availability, power system planners have big concern on EEG （expected energy generation） and system reliability of power system with wind generators. This paper presents a meth...Due to randomness of wind generator＇s availability, power system planners have big concern on EEG （expected energy generation） and system reliability of power system with wind generators. This paper presents a methodology to evaluate the EEG as well as overall LOLP （loss of load probability）, which is an index for system reliability of multi-area interconnected systems with wind generators, as well as conventional fossil fuel based generating units. The proposed model is also capable of tracking the energy export incorporating the multi-state probability model for wind generator which output varies with time and season.展开更多
Offshore wind energy is an important part of clean energy,and the adoption of wind energy to generate electricity will contribute to the implementation of the carbon peaking and carbon neutrality goals.The combination...Offshore wind energy is an important part of clean energy,and the adoption of wind energy to generate electricity will contribute to the implementation of the carbon peaking and carbon neutrality goals.The combination of the fractional frequency transmission system(FFTS) and the direct-drive wind turbine generator will be beneficial to the development of the offshore wind power industry.The use of fractional frequency in FFTS is beneficial to the transmission of electrical energy,but it will also lead to an increase in the volume and weight of the generator,which is unfavorable for wind power generation.Improving the torque density of the generator can effectively reduce the volume of the generators.The vernier permanent magnet machine(VPM) operates on the magnetic flux modulation principle and has the merits of high torque density.In the field of electric machines,the vernier machine based on the principle of magnetic flux modulation has been proved its feasibility to reduce the volume and weight.However,in the field of low-speed direct-drive machines for high-power fractional frequency power generation,there are still few related researches.Therefore,this paper studies the application of magnetic flux modulation in fractional frequency and high-power direct-drive wind turbine generators,mainly analyzes the influence of different pole ratios and different pole pairs on the generator,and draws some conclusions to provide reference for the design of wind turbine generators.展开更多
The installation of wind power generators on buildings located in areas with regular winds may be a suitable investment in a renewable power source. Brazil has a high eolic potential, where the annual mean wind speed ...The installation of wind power generators on buildings located in areas with regular winds may be a suitable investment in a renewable power source. Brazil has a high eolic potential, where the annual mean wind speed may reach over eight meters per second. This case study is aimed to assess the economic feasibility of the installation of small wind power plants in urban areas. This work evaluates a project for the installation of a vertical axis wind turbine in three buildings （15-, 22-, and 26-story） including the following stages： （1） installation of a real-time power meter in the 15-store unit; （2） demand analysis of the 26-store building＇s power consumption; （3） winds survey along the coast of the State of Ceara; （4） analysis of the wind turbines available in the market; （5） simulation aimed to choose the system. Vertical wind power generators offer better conditions of use in urban areas. The turnover time was established to be between four and six years in the three studied units. The installation of a wind power generator on buildings in regions with an adequate eolic regimen reaches a financial return of the investment before the end of the equipment＇s lifespan.展开更多
This paper presents an analysis of a pre-feasibility study of a 10 MW offshore wind power project in Nakhon Si Thammarat province, southern Thailand. The wind speeds at the hub heights of large scale wind turbine gene...This paper presents an analysis of a pre-feasibility study of a 10 MW offshore wind power project in Nakhon Si Thammarat province, southern Thailand. The wind speeds at the hub heights of large scale wind turbine generators （WTG）, i.e. 80-100 m, were extrapolated using monthly mean wind shear coefficients and the l/7th exponent. Using WAsP 9.0, the annual energy production from several models of offshore wind farms using different WTG was analyzed. The capacity factor and the cost of energy were then computed. Using best available estimates, the analysis shows that the estimated annual mean offshore wind speeds at 80-100 m were in the range of 6.4 and 8.3 m/s. The annual energy production by the wind farm from nine models of wind turbine generators were in the range of 20-39 GWh/year, corresponding to a capacity factor in the range of 26-46%, while the cost of energy was 12-15 US cent/kWh.展开更多
This paper describes a small wind turbine generation system with SynRG （synchronous reluctance generator）. SynRGs are robust and inexpensive. In addition, SynRG has no cogging torque. Hence, wind turbine generation ...This paper describes a small wind turbine generation system with SynRG （synchronous reluctance generator）. SynRGs are robust and inexpensive. In addition, SynRG has no cogging torque. Hence, wind turbine generation system with SynRG can achieve smooth start at low wind velocity. The rotor design of proposed SynRG is multi flux barrier type. With FEA （finite element analysis） software, the characteristics of SynRG are brought out, and the performance of wind turbine generation system with SynRG including copper loss and iron loss is simulated by FEA coupled with the motion equation of the wind turbine generation system under the maximum power point tracking control. In this paper, the constant wind test and the quasi-natural wind test are conducted. In conclusion, the results of these simulations indicate that the wind turbine generation system with SynRG has good performance, especially in starting phenomena.展开更多
In order to improve the accuracy of wind turbine fault diagnosis,a wind turbine fault diagnosis method based on Subtraction-Average-Based Optimizer(SABO)optimized Variational Mode Decomposition(VMD)and Kernel Extreme ...In order to improve the accuracy of wind turbine fault diagnosis,a wind turbine fault diagnosis method based on Subtraction-Average-Based Optimizer(SABO)optimized Variational Mode Decomposition(VMD)and Kernel Extreme Learning Machine(KELM)is proposed.Firstly,the SABO algorithm was used to optimize the VMD parameters and decompose the original signal to obtain the best modal components,and then the nine features were calculated to obtain the feature vectors.Secondly,the SABO algorithm was used to optimize the KELM parameters,and the training set and the test set were divided according to different proportions.The results were compared with the optimized model without SABO algorithm.The experimental results show that the fault diagnosis method of wind turbine based on SABO-VMD-KELM model can achieve fault diagnosis quickly and effectively,and has higher accuracy.展开更多
基金supported in part by the“Chunhui Plan”Collaborative Research Project of Chinese Ministry of Education under Grant HZKY20220604by the National Natural Science Foundation of China under Grant 52107007。
文摘With the continuous improvement of permanent magnet(PM)wind generators'capacity and power density,the design of reasonable and efficient cooling structures has become a focus.This paper proposes a fully enclosed self-circulating hydrogen cooling structure for a originally forced-air-cooled direct-drive PM wind generator.The proposed hydrogen cooling system uses the rotor panel supports that hold the rotor core as the radial blades,and the hydrogen flow is driven by the rotating plates to flow through the axial and radial vents to realize the efficient cooling of the generator.According to the structural parameters of the cooling system,the Taguchi method is used to decouple the structural variables.The influence of the size of each cooling structure on the heat dissipation characteristic is analyzed,and the appropriate cooling structure scheme is determined.
基金partly supported by the National Natural Science Foundation of China under Grants No.61473061 and No.61104104the Sichuan Science and Technology Program under Grant No.2020YFSY0012the Program for New Century Excellent Talents in University under Grant No.NCET-13-0091。
文摘The electromagnetic characteristics and iron loss of a high-temperature superconductor wind generator(HWG)equipped with an overlapped field coil arrangement(OFCA)are studied by comparing with the one equipped with the conventional field coil arrangement(CFCA).Through a quantitative analysis,it was found that HWG with OFCA exhibits better electromagnetic characteristics than HWG with CFCA and can reduce the iron loss by eliminating the magnetic flux sag caused by the adjacent field coil sides with the same current flow direction.In addition,the OFCA topology can further reduce the volume of the wind generator.
文摘This paper investigates the function of doubly-fed asynchronous machine(DASM)with emphasis placed on its ability to the stabilization of the power system including wind generators.P(active power)and Q(reactive power)compensation from DASM can be regulated independently through secondary-excitation controlling.Simulation results by power system computer aided design(PSCAD)show that DASM can restore the wind-generator system to a normal operating condition rapidly even following severe transmission-line failures.Comparison studies have also been performed between wind turbine pitch control and proposed method.
文摘With the rapid increase of wind farms,the grid code needs to be improved to meet the requirement of wind farms and enhance grid stability.Doubly-fed induction generators are largely used in wind turbines,but they are very sensitive to grid disturbances.The voltage swell can be caused by switching on capacitor banks or switching off large loads,which may result in the reversal of the power flow in the grid convertor;the current may flow from the grid into the DC link,which may step up DC voltage,and result in large faults of rotor currents and instantaneous power oscillation.The grid reactive compensation devices can not have the automatic swithing function after the low voltage fault,which will result in local reactive power surplus,so some wind power generators will retreat from the grid under high voltage protection.
文摘The wind energy generation,utilization and its grid penetration in electrical grid are increasing world-wide.The wind generated power is always fluctuating due to its time varying nature and causing stability problem.This weak interconnection of wind generating source in the electrical network affects the power quality and reliability.The localized energy storages shall compensate the fluctuating power and support to strengthen the wind generator in the power system.In this paper,it is proposed to control the voltage source inverter （VSI） in current control mode with energy storage,that is,batteries across the dc bus.The generated wind power can be extracted under varying wind speed and stored in the batteries.This energy storage maintains the stiff voltage across the dc bus of the voltage source inverter.The proposed scheme enhances the stability and reliability of the power system and maintains unity power factor.It can also be operated in stand-alone mode in the power system.The power exchange across the wind generation and the load under dynamic situation is feasible while maintaining the power quality norms at the common point of coupling.It strengthens the weak grid in the power system.This control strategy is evaluated on the test system under dynamic condition by using simulation.The results are verified by comparing the performance of controllers.
文摘In the early development of the wind energy, the majority of the wind turbines have been operated at constant speed. Subsequently, the number of variable-speed wind turbines installed in wind farms has increased. In this paper, a comparative performance of fixed and variable speed wind generators with Pitch angle control has been presented. The first is based on a squirrel cage Induction Generator （IG） of 315 kW rated power, connected directly to the grid. The second incorporated a Permanent Magnet Synchronous Generator （PMSG） of 750 kW rated power. The performances of each studied wind generator are evaluated by simulation works and variable speed operation is highlighted as preferred mode of operation.
基金supported by the National Nature Science Foundation of China(51407068).
文摘This paper reviews the status and progress of the investigation on power system small-signal angular stability as affected by grid-connected variable speed wind generators(VSWGs).The review is carried out on the basis of a survey of recently published representative papers.Strategies of the investigation made in those selected papers are classified into two groups:1)VSWGs displacing synchronous generators(SGs);2)VSWGs simply being added in a power system.The diversification of the results of the investigation is highlighted in the survey.Careful analysis on two strategies of the investigation is conducted in this paper.It is revealed that in the strategy of VSWGs displacing SGs,there are two factors which could affect power system small-signal angular stability differently:1)Withdrawing the SGs’dynamics;2)adding the VSWGs’dynamics.In the strategy of adding VSWGs in the power system,there are also two affecting factors:1)Change of load flow brought about by the VSWGs;2)dynamic interactions with the SGs introduced by the VSWGs.Hence diversified results of the investigation obtained so far are not only due to the dependence of the investigation on sample power systems used,but also caused by the mixture of different affecting factors.This paper is concluded with a summary of key issues of the investigation for future work.
基金supported by Natural Science Foundation of Hebei Province(No. F2012203088)
文摘According to the increasing requirement of the wind energy utilization and the dynamic stability in the variable speed variable pitch wind power generation system, a linear parameter varying （LPV） system model is established and a new adaptive robust guaranteed cost controller （AGCC） is proposed in this paper. First, the uncertain parameters of the system are estimated by using the adaptive method, then the estimated uncertain parameters and robust guaranteed cost control method are used to design a state feedback controller. The controller s feedback gain is obtained by solving a set of linear matrix inequality （LMI） constraints, such that the controller can meet a quadratic performance evaluation criterion. The simulation results show that we can realize the goal of maximum wind energy capture in low wind speed by the optimal torque control and constant power control in high wind speed by variable pitch control with good dynamic characteristics, robustness and the ability of suppressing disturbance.
基金This project is supported by Provincial Science Foundation of Education Office of Hebei(No.Z2004455)Youth Research Fundation of State Power of China(No.SPQKJ02-10).
文摘Rotor vibration characteristics are first analyzed, which are that the rotor vibration of fundamental frequency will increase due to rotor winding inter-turn short circuit fault, air-gap dynamic eccentricity fault, or imbalance fault, and the vibration of the second frequency will increase when the air-gap static eccentricity fault occurs. Next, the characteristics of the stator winding parallel branches circulating current are analyzed, which are that the second harmonics circulating current will increase when the rotor winding inter-turn short circuit fault occurs, and the fundamental circulating current will increase when the air-gap eccentricity fault occurs, neither being strongly affected by the imbalance fault. Considering the differences of the rotor vibration and circulating current characteristics caused by different rotor faults, a method of generator vibration fault diagnosis, based on rotor vibration and circulating current characteristics, is developed. Finally, the rotor vibration and circulating current of a type SDF-9 generator is measured in the laboratory to verify the theoretical analysis presented above.
文摘A distribution grid is generally characterized by a high R/X （resistance/reactance） ratio and it is radial in nature. By design, a distribution grid system is not an active network, and it is normally designed in such a way that power flows from transmission system via distribution system to consumers. But in a situation when wind turbines are connected to the distribution grid, the power source will change from one source to two sources, in this case, network is said to be active. This may probably have an impact on the distribution grid to whenever the wind turbine is connected. The best way to know the impact of wind turbine on the distribution grid in question is by carrying out load flow analysis on that system with and without the connection of wind turbines. Two major fundamental calculations： the steady-state voltage variation at the PCC （point of common coupling） and the calculation of short-circuit power of the grid system at the POC （point of connection） are necessary before carrying out the load flow study on the distribution grid. This paper, therefore, considers these pre-load flow calculations that are necessary before carrying out load flow study on the test distribution grid. These calculations are carded out on a test distribution system.
基金Science & Technology Development Foundation of Shanghai,China(No.062158017)Postdoctoral Foundation of Shanghai,China(No.05R214133)Postdoctoral Foundation of China(No.2005038435)
文摘The control strategy is one of the most important renewable technology,and an increasing number of multi-MW wind turbines are being developed with a variable speed-variable pitch(VS-VP)technology.The main objective of adopting a VS-VP technology is to improve the fast response speed and capture maximum energy.But the power generated by wind turbine changes rapidly because of the continuous fluctuation of wind speed and direction.At the same time,wind energy conversion systems are of high order,time delays and strong nonlinear characteristics because of many uncertain factors.Based on analyzing the all dynamic processes of wind turbine,a kind of layered multi-mode optimal control strategy is presented which is that three control strategies:bang-bang,fuzzy and adaptive proportional integral derivative(PID)are adopted according to different stages and expected performance of wind turbine to capture optimum wind power,compensate the nonlinearity and improve the wind turbine performance at low,rated and high wind speed.
基金supported in part by the National Key R&D Program of China(No.2021YFB1506904)the National Natural Science Foundation of China(No.51977111).
文摘The optimal torque(OT)method,which is preferred for its simplicity,is widely employed in maximum power point tracking(MPPT)control strategies for wind energy capture in wind turbine generators(WTGs).Based on the OT method,the decreased torque gain(DTG)method is developed to improve turbine acceleration through a reduction of the torque gain coefficient.However,the DTG method does not fully align with the acceleration performance required by wind turbines,which subsequently limits improvements in wind energy capture efficiency.To address these concerns,a novel MPPT control strategy is proposed,which introduces redefined torque curve and torque command conceptualized based on a higher-order function relative to rotor speed.Additionally,an adaptive algorithm for the periodic update of the torque command is suggested to better accommodate the variability of turbulent wind speeds,thus aiming to improve the wind energy capture efficiency.The effectiveness of the proposed MPPT control strategy is substantiated through the wind turbine simulator(WTS)-based experiments.
文摘The impact of large-scale grid-connected renewable power sources, such as wind generators and solar photovoitaic systems, on transient stability of synchronous generators is discussed in this paper. The permanent magnet synchronous generator with variable speed wind turbine is used in the simulation analysis as a wind generator model. The transient stability analysis is performed for IEEE 9-bus system model with high-penetration renewable power sources. The effect of FRT （fault ride-through） capability implemented for each power source on the transient stability is investigated.
文摘Wind energy is currently a fast-growing interdisciplinary field that encompasses many different branches of engineering and science. Modeling and controlling wind energy systems are difficult and challenging problems. The basic structure of wind turbines and some wind control system methods are briefly reviewed. The need for using advanced theories from fuzzy and intelligent systems in studying wind energy systems is identified and justified. FCMs （fuzzy cognitive maps） are used to model wind energy systems. Simulation studies are performed and obtained results are discussed. A new mathematical approach has been proposed to model dynamical complex systems, the DYFUKN （dynamic fuzzy knowledge networks）. Many open problems in the areas of modeling and controlling wind energy systems are outlined.
文摘Due to randomness of wind generator＇s availability, power system planners have big concern on EEG （expected energy generation） and system reliability of power system with wind generators. This paper presents a methodology to evaluate the EEG as well as overall LOLP （loss of load probability）, which is an index for system reliability of multi-area interconnected systems with wind generators, as well as conventional fossil fuel based generating units. The proposed model is also capable of tracking the energy export incorporating the multi-state probability model for wind generator which output varies with time and season.
基金supported by the Science and Technology Foundation of SGCC (5500-202099509A-0-0-00)“Research on Fractional Frequency Transmission Technology for Largely Enhancing Transmission Capacity and Development of Its Key Devices”。
文摘Offshore wind energy is an important part of clean energy,and the adoption of wind energy to generate electricity will contribute to the implementation of the carbon peaking and carbon neutrality goals.The combination of the fractional frequency transmission system(FFTS) and the direct-drive wind turbine generator will be beneficial to the development of the offshore wind power industry.The use of fractional frequency in FFTS is beneficial to the transmission of electrical energy,but it will also lead to an increase in the volume and weight of the generator,which is unfavorable for wind power generation.Improving the torque density of the generator can effectively reduce the volume of the generators.The vernier permanent magnet machine(VPM) operates on the magnetic flux modulation principle and has the merits of high torque density.In the field of electric machines,the vernier machine based on the principle of magnetic flux modulation has been proved its feasibility to reduce the volume and weight.However,in the field of low-speed direct-drive machines for high-power fractional frequency power generation,there are still few related researches.Therefore,this paper studies the application of magnetic flux modulation in fractional frequency and high-power direct-drive wind turbine generators,mainly analyzes the influence of different pole ratios and different pole pairs on the generator,and draws some conclusions to provide reference for the design of wind turbine generators.
文摘The installation of wind power generators on buildings located in areas with regular winds may be a suitable investment in a renewable power source. Brazil has a high eolic potential, where the annual mean wind speed may reach over eight meters per second. This case study is aimed to assess the economic feasibility of the installation of small wind power plants in urban areas. This work evaluates a project for the installation of a vertical axis wind turbine in three buildings （15-, 22-, and 26-story） including the following stages： （1） installation of a real-time power meter in the 15-store unit; （2） demand analysis of the 26-store building＇s power consumption; （3） winds survey along the coast of the State of Ceara; （4） analysis of the wind turbines available in the market; （5） simulation aimed to choose the system. Vertical wind power generators offer better conditions of use in urban areas. The turnover time was established to be between four and six years in the three studied units. The installation of a wind power generator on buildings in regions with an adequate eolic regimen reaches a financial return of the investment before the end of the equipment＇s lifespan.
文摘This paper presents an analysis of a pre-feasibility study of a 10 MW offshore wind power project in Nakhon Si Thammarat province, southern Thailand. The wind speeds at the hub heights of large scale wind turbine generators （WTG）, i.e. 80-100 m, were extrapolated using monthly mean wind shear coefficients and the l/7th exponent. Using WAsP 9.0, the annual energy production from several models of offshore wind farms using different WTG was analyzed. The capacity factor and the cost of energy were then computed. Using best available estimates, the analysis shows that the estimated annual mean offshore wind speeds at 80-100 m were in the range of 6.4 and 8.3 m/s. The annual energy production by the wind farm from nine models of wind turbine generators were in the range of 20-39 GWh/year, corresponding to a capacity factor in the range of 26-46%, while the cost of energy was 12-15 US cent/kWh.
文摘This paper describes a small wind turbine generation system with SynRG （synchronous reluctance generator）. SynRGs are robust and inexpensive. In addition, SynRG has no cogging torque. Hence, wind turbine generation system with SynRG can achieve smooth start at low wind velocity. The rotor design of proposed SynRG is multi flux barrier type. With FEA （finite element analysis） software, the characteristics of SynRG are brought out, and the performance of wind turbine generation system with SynRG including copper loss and iron loss is simulated by FEA coupled with the motion equation of the wind turbine generation system under the maximum power point tracking control. In this paper, the constant wind test and the quasi-natural wind test are conducted. In conclusion, the results of these simulations indicate that the wind turbine generation system with SynRG has good performance, especially in starting phenomena.
文摘In order to improve the accuracy of wind turbine fault diagnosis,a wind turbine fault diagnosis method based on Subtraction-Average-Based Optimizer(SABO)optimized Variational Mode Decomposition(VMD)and Kernel Extreme Learning Machine(KELM)is proposed.Firstly,the SABO algorithm was used to optimize the VMD parameters and decompose the original signal to obtain the best modal components,and then the nine features were calculated to obtain the feature vectors.Secondly,the SABO algorithm was used to optimize the KELM parameters,and the training set and the test set were divided according to different proportions.The results were compared with the optimized model without SABO algorithm.The experimental results show that the fault diagnosis method of wind turbine based on SABO-VMD-KELM model can achieve fault diagnosis quickly and effectively,and has higher accuracy.
