An economic dispatch problem for power system with wind power is discussed.Using discrete scenario to describe uncertain wind powers,a threshold is given to identify bad scenario set.The bad-scenario-set robust econom...An economic dispatch problem for power system with wind power is discussed.Using discrete scenario to describe uncertain wind powers,a threshold is given to identify bad scenario set.The bad-scenario-set robust economic dispatch model is established to minimize the total penalties on bad scenarios.A specialized hybrid particle swarm optimization(PSO)algorithm is developed through hybridizing simulated annealing(SA)operators.The SA operators are performed according to a scenario-oriented adaptive search rule in a neighborhood which is constructed based on the unit commitment constraints.Finally,an experiment is conducted.The computational results show that the developed algorithm outperforms the existing algorithms.展开更多
Because of the large-scale integration of wind power,the dynamic characteristics of power system have many uncertain effects.Based on deterministic analysis methods,traditional on-line security assessment system canno...Because of the large-scale integration of wind power,the dynamic characteristics of power system have many uncertain effects.Based on deterministic analysis methods,traditional on-line security assessment system cannot quantitatively estimate the actual operating conditions of the power system for only considering the most serious and credible accidents.Therefore,the risk theory is introduced into an on-line security assessment system and then an on-line risk assessment system for wind power is designed and implemented by combining with the dynamic security assessment system.Based on multiple data integration,the wind power disturbance probability is available and the security assessment of the power grid can obtain security indices in different aspects.The operating risk index is an expectation of severity,computed by summing up all the products of the result probability and its severity.Analysis results are reported to the dispatchers in on-line environment,while the comprehensive weak links are automatically provided to the power dispatching center.The risk assessment system in operation can verify the reasonableness of the system.展开更多
The traditional voltage stability analysis method is mostly based on the deterministic mode1.and ignores the uncertainties of bus loads,power supplies,changes in network configuration and so on.However,the great expan...The traditional voltage stability analysis method is mostly based on the deterministic mode1.and ignores the uncertainties of bus loads,power supplies,changes in network configuration and so on.However,the great expansion of renewable power generations such as wind and solar energy in a power system has increased their uncertainty,and仃aditional techniques are limited in capturing their variable behavior.This leads to greater needs of new techniques and methodologies to properly quan tify the voltage stability of power systems.展开更多
The characteristics of induction generator based fixed-speed wind turbines(FSWT)are investigated.The impacts of different execution time in protective operations are studied under different fault duration and various ...The characteristics of induction generator based fixed-speed wind turbines(FSWT)are investigated.The impacts of different execution time in protective operations are studied under different fault duration and various wind velocity situations,e.g.,FSWT stabilities of load shedding in distribution systems.Based on this research,a dynamic protective control strategy for a distributed generation system(DGS)with FSWT is proposed.Finally,simulation results demonstrate the effectiveness of the strategy.展开更多
The probability distributions of wind speeds and the availability of wind turbines were investigated by considering the vertical wind shear. Based on the wind speed data at the standard height observed at a wind farm,...The probability distributions of wind speeds and the availability of wind turbines were investigated by considering the vertical wind shear. Based on the wind speed data at the standard height observed at a wind farm, the power-law process was used to simulate the wind speeds at a hub height of 60 m. The Weibull and Rayleigh distributions were chosen to express the wind speeds at two different heights. The parameters in the model were estimated via the least square(LS) method and the maximum likelihood estimation(MLE) method, respectively. An adjusted MLE approach was also presented for parameter estimation. The main indices of wind energy characteristics were calculated based on observational wind speed data. A case study based on the data of Hexi area, Gansu Province of China was given. The results show that MLE method generally outperforms LS method for parameter estimation, and Weibull distribution is more appropriate to describe the wind speed at the hub height.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
Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct...Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.展开更多
A novel fault ride-through strategy for wind turbines,based on permanent magnet synchronous generator,has been proposed.The proposed strategy analytically formulates the reference current signals,disregarding grid fau...A novel fault ride-through strategy for wind turbines,based on permanent magnet synchronous generator,has been proposed.The proposed strategy analytically formulates the reference current signals,disregarding grid fault type and utilizes the whole system capacity to inject the reactive current required by grid codes and deliver maximum possible active power to support grid frequency and avoid generation loss.All this has been reached by taking the grid-side converter’s phase current limit into account.The strategy is compatible with different countries’grid codes and prevents pulsating active power injection,in an unbalanced grid condition.Model predictive current controller is applied to handling rapid transients.During faults,the energy storage system maintains DC-link voltage,which causes voltage fluctuations to be eliminated,significantly.A fault ride-through strategy was proposed for PMSG-based wind turbines,neglecting fault characteristics,second,reaching maximum possible grid support in faulty grid conditions,while avoiding over-current and third,considerable reduction in energy storage system size and power rating.Inspiring simulations have been carried out through MATLAB/SIMULINK to validate the feasibility and competency of the proposed fault ride-through method and efficiency of the entire control system.展开更多
静态电压稳定性是一种理想化的稳定性概念,其扰动无限小的假设不利于强非线性的电力系统在静态电压稳定域(steady-state voltage stability region,SVSR)内的安全运行。针对功率大扰动场景下由SVSR内的边界危机所引发的吸引域骤缩问题,...静态电压稳定性是一种理想化的稳定性概念,其扰动无限小的假设不利于强非线性的电力系统在静态电压稳定域(steady-state voltage stability region,SVSR)内的安全运行。针对功率大扰动场景下由SVSR内的边界危机所引发的吸引域骤缩问题,提出了一种考虑边界危机的电压稳定域(voltage stability region considering boundary crises,BCVSR)的划分方法。首先通过流形分析研究了边界危机的发生机理及其对电压稳定性的影响。其次通过相轨迹分析验证了理论研究的结果。然后通过分岔分析研究了参数变化对直驱风电并网系统的平衡集及动态特性的影响。最后划分了系统在注入功率空间中的单参数与双参数BCVSR,并将其与SVSR进行了对比。研究结果表明,在考虑功率大扰动的情形下,BCVSR的划分排除了SVSR内的边界危机对系统电压稳定性的威胁,有助于指导电力系统在实际运行中的功率调整。展开更多
基金supported by the National Natural Science Foundation of China(62173219,62073210).
文摘An economic dispatch problem for power system with wind power is discussed.Using discrete scenario to describe uncertain wind powers,a threshold is given to identify bad scenario set.The bad-scenario-set robust economic dispatch model is established to minimize the total penalties on bad scenarios.A specialized hybrid particle swarm optimization(PSO)algorithm is developed through hybridizing simulated annealing(SA)operators.The SA operators are performed according to a scenario-oriented adaptive search rule in a neighborhood which is constructed based on the unit commitment constraints.Finally,an experiment is conducted.The computational results show that the developed algorithm outperforms the existing algorithms.
基金supported by National High Technology Research and Development Program of China (863 Program) (No.2011AA05A118)
文摘Because of the large-scale integration of wind power,the dynamic characteristics of power system have many uncertain effects.Based on deterministic analysis methods,traditional on-line security assessment system cannot quantitatively estimate the actual operating conditions of the power system for only considering the most serious and credible accidents.Therefore,the risk theory is introduced into an on-line security assessment system and then an on-line risk assessment system for wind power is designed and implemented by combining with the dynamic security assessment system.Based on multiple data integration,the wind power disturbance probability is available and the security assessment of the power grid can obtain security indices in different aspects.The operating risk index is an expectation of severity,computed by summing up all the products of the result probability and its severity.Analysis results are reported to the dispatchers in on-line environment,while the comprehensive weak links are automatically provided to the power dispatching center.The risk assessment system in operation can verify the reasonableness of the system.
文摘The traditional voltage stability analysis method is mostly based on the deterministic mode1.and ignores the uncertainties of bus loads,power supplies,changes in network configuration and so on.However,the great expansion of renewable power generations such as wind and solar energy in a power system has increased their uncertainty,and仃aditional techniques are limited in capturing their variable behavior.This leads to greater needs of new techniques and methodologies to properly quan tify the voltage stability of power systems.
基金supported by the Danish Academy of Wind Energy(DAWE)
文摘The characteristics of induction generator based fixed-speed wind turbines(FSWT)are investigated.The impacts of different execution time in protective operations are studied under different fault duration and various wind velocity situations,e.g.,FSWT stabilities of load shedding in distribution systems.Based on this research,a dynamic protective control strategy for a distributed generation system(DGS)with FSWT is proposed.Finally,simulation results demonstrate the effectiveness of the strategy.
基金Project(51165019)supported by the National Natural Science Foundation of ChinaProject(1308RJYA018)supported by Gansu Provincial Natural Science Fund,ChinaProject(2013-4-110)supported by Lanzhou Technology Development Program,China
文摘The probability distributions of wind speeds and the availability of wind turbines were investigated by considering the vertical wind shear. Based on the wind speed data at the standard height observed at a wind farm, the power-law process was used to simulate the wind speeds at a hub height of 60 m. The Weibull and Rayleigh distributions were chosen to express the wind speeds at two different heights. The parameters in the model were estimated via the least square(LS) method and the maximum likelihood estimation(MLE) method, respectively. An adjusted MLE approach was also presented for parameter estimation. The main indices of wind energy characteristics were calculated based on observational wind speed data. A case study based on the data of Hexi area, Gansu Province of China was given. The results show that MLE method generally outperforms LS method for parameter estimation, and Weibull distribution is more appropriate to describe the wind speed at the hub height.
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.
基金Project(HEUCF110707)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(E201216)supported by Heilongjiang Natural Science Fund,China
文摘Wind energy is one of the most promising renewable energy sources, straight-bladed vertical axis wind turbine(S-VAWT) appears to be particularly promising for the shortage of fossil fuel reserves owing to its distinct advantages, but suffers from poor self-starting and low power coefficient. Variable-pitch method was recognized as an attractive solution to performance improvement, thus majority efforts had been devoted into blade pitch angle effect on aerodynamic performance. Taken into account the local flow field of S-VAWT, mathematical model was built to analyze the relationship between power outputs and pitch angle. Numerical simulations on static and dynamic performances of blade were carried out and optimized pitch angle along the rotor were presented. Comparative analyses of fixed pitch and variable-pitch S-VAWT were conducted, and a considerable improvement of the performance was obtained by the optimized blade pitch angle, in particular, a relative increase of the power coefficient by more than 19.3%. It is further demonstrated that the self-starting is greatly improved with the optimized blade pitch angle.
文摘A novel fault ride-through strategy for wind turbines,based on permanent magnet synchronous generator,has been proposed.The proposed strategy analytically formulates the reference current signals,disregarding grid fault type and utilizes the whole system capacity to inject the reactive current required by grid codes and deliver maximum possible active power to support grid frequency and avoid generation loss.All this has been reached by taking the grid-side converter’s phase current limit into account.The strategy is compatible with different countries’grid codes and prevents pulsating active power injection,in an unbalanced grid condition.Model predictive current controller is applied to handling rapid transients.During faults,the energy storage system maintains DC-link voltage,which causes voltage fluctuations to be eliminated,significantly.A fault ride-through strategy was proposed for PMSG-based wind turbines,neglecting fault characteristics,second,reaching maximum possible grid support in faulty grid conditions,while avoiding over-current and third,considerable reduction in energy storage system size and power rating.Inspiring simulations have been carried out through MATLAB/SIMULINK to validate the feasibility and competency of the proposed fault ride-through method and efficiency of the entire control system.
文摘静态电压稳定性是一种理想化的稳定性概念,其扰动无限小的假设不利于强非线性的电力系统在静态电压稳定域(steady-state voltage stability region,SVSR)内的安全运行。针对功率大扰动场景下由SVSR内的边界危机所引发的吸引域骤缩问题,提出了一种考虑边界危机的电压稳定域(voltage stability region considering boundary crises,BCVSR)的划分方法。首先通过流形分析研究了边界危机的发生机理及其对电压稳定性的影响。其次通过相轨迹分析验证了理论研究的结果。然后通过分岔分析研究了参数变化对直驱风电并网系统的平衡集及动态特性的影响。最后划分了系统在注入功率空间中的单参数与双参数BCVSR,并将其与SVSR进行了对比。研究结果表明,在考虑功率大扰动的情形下,BCVSR的划分排除了SVSR内的边界危机对系统电压稳定性的威胁,有助于指导电力系统在实际运行中的功率调整。
