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不平衡电网电压下双馈感应发电机网侧和转子侧变换器的协同控制 被引量:62
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作者 胡家兵 贺益康 +1 位作者 王宏胜 lie xu 《中国电机工程学报》 EI CSCD 北大核心 2010年第9期97-104,共8页
建立了不平衡电网电压下双馈感应发电机(doubly-fed induction generator,DFIG)网侧变换器的数学模型,讨论了交流输入电抗对瞬时有功功率的影响,在此基础上,提出4种可供选择的网侧变换器协同控制目标。为了验证网侧、转子侧变换器协同... 建立了不平衡电网电压下双馈感应发电机(doubly-fed induction generator,DFIG)网侧变换器的数学模型,讨论了交流输入电抗对瞬时有功功率的影响,在此基础上,提出4种可供选择的网侧变换器协同控制目标。为了验证网侧、转子侧变换器协同控制策略的有效性,提出静止αβ坐标系中比例?谐振控制器,使网侧变换器正、负序电流无需分解调节,并构建了DFIG网侧变换器的不平衡控制系统。仿真和实验研究结果表明,所提网侧、转子侧变换器协同控制策略可实现风电机组更为优化的不对称故障穿越(不间断)运行控制;所设计的网侧、转子侧变换器P-R电流控制方案不仅能够在稳态不平衡电网下提供精确的电流调节,而且在瞬态不平衡下体现优良的动态响应特性。 展开更多
关键词 电压不平衡 风力发电 双馈感应发电机 网侧变换器 协同控制 比例-谐振控制 不对称故障穿越(不间断)运行
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不平衡电网电压下双馈感应发电机转子侧变换器的比例–谐振电流控制策略 被引量:70
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作者 胡家兵 贺益康 +1 位作者 王宏胜 lie xu 《中国电机工程学报》 EI CSCD 北大核心 2010年第6期48-56,共9页
为了研究不平衡电网电压条件下双馈感应风力发电机(doubly-fedinduction generator,DFIG)系统增强运行能力的有效控制策略,提出了网侧、转子侧变换器的比例–谐振电流控制方案以及两者之间的协同控制策略。针对电网电压不平衡条件下DFI... 为了研究不平衡电网电压条件下双馈感应风力发电机(doubly-fedinduction generator,DFIG)系统增强运行能力的有效控制策略,提出了网侧、转子侧变换器的比例–谐振电流控制方案以及两者之间的协同控制策略。针对电网电压不平衡条件下DFIG转子侧变换器,提出了一种在两相定子静止αβ坐标系中实施的比例–谐振(proportional-resonant,P-R)电流控制方案,以实现对DFIG转子电流无需正、负相序分解的统一调节。采用正序d+轴电网电压定向简化了各种增强运行能力控制目标下的转子正、负序电流指令值算法,设计了相应的DFIG不平衡控制策略。实验研究表明,这种P-R电流控制方案能够实现转子侧变换器选定控制目标,具备优良的动态调节性能,可增强不平衡电网电压故障下DFIG风力发电机系统的不间断运行能力。 展开更多
关键词 电压不平衡 风力发电 双馈感应发电机 转子侧变换器 比例–谐振控制器 故障下不间断运行
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大量风电引入电网时的频率控制特性 被引量:64
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作者 韩民晓 崔军立 +1 位作者 姚蜀军 lie xu 《电力系统自动化》 EI CSCD 北大核心 2008年第1期29-33,共5页
大量风力发电引入电网时,会对电网的频率控制带来影响。在深入分析异步电动机频率特性的基础上,采用所开发的电力扰动装置对不同转矩特性的异步电动机的频率特性进行了测试。基于加权综合的思路建立了包含异步电动机的综合负荷的频率特... 大量风力发电引入电网时,会对电网的频率控制带来影响。在深入分析异步电动机频率特性的基础上,采用所开发的电力扰动装置对不同转矩特性的异步电动机的频率特性进行了测试。基于加权综合的思路建立了包含异步电动机的综合负荷的频率特性模型。同时分析了风力发电的出力特性。通过对一个包含风力发电的电网进行分析,论证了考虑负荷频率特性以后,在同样电网调频能力的情况下,频率波动的偏差会变小。 展开更多
关键词 风力发电 电能质量 频率控制 负荷特性
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多端直流系统分区协调保护策略 被引量:11
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作者 吴婧 姚良忠 +3 位作者 王志冰 Md Habibur RAHMAN lie xu 鲁宗相 《电力系统自动化》 EI CSCD 北大核心 2017年第4期105-112,共8页
针对多端直流系统的故障保护问题,首先分析了直流故障特性及多端直流系统保护难点,总结了现有多端直流系统故障保护方法。然后,基于一种典型的多端直流系统拓扑结构,以使用最少数量直流断路器为目标,提出了多端直流系统区域保护划分原... 针对多端直流系统的故障保护问题,首先分析了直流故障特性及多端直流系统保护难点,总结了现有多端直流系统故障保护方法。然后,基于一种典型的多端直流系统拓扑结构,以使用最少数量直流断路器为目标,提出了多端直流系统区域保护划分原则和分区保护策略。该方法将直流故障区域通过直流断路器与非故障区域进行隔离,从而使非故障区域可以继续维持正常运行,而故障区域则通过换流站交流侧断路器和直流侧开关进行保护和隔离。最后,通过MATLAB/Simulink仿真平台建模及仿真分析,验证了多端直流系统分区保护的有效性和经济性。 展开更多
关键词 多端直流系统 直流故障特性 直流断路器 直流区域划分
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一种开关磁阻风力发电机最大风能跟踪方法 被引量:19
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作者 熊立新 徐丙垠 +1 位作者 高厚磊 lie xu 《电工技术学报》 EI CSCD 北大核心 2009年第11期1-7,共7页
对开关磁阻风力发电机的运行原理和风轮机的功率输出特性进行了介绍,提出了一种不依赖风轮机运行参数即可实现最大风能自动跟踪的变步长控制方法。使用Matlab/Simulink构建了整个系统的模型,进行了仿真,使用直流电动机模拟风力机对提出... 对开关磁阻风力发电机的运行原理和风轮机的功率输出特性进行了介绍,提出了一种不依赖风轮机运行参数即可实现最大风能自动跟踪的变步长控制方法。使用Matlab/Simulink构建了整个系统的模型,进行了仿真,使用直流电动机模拟风力机对提出的最大风能跟踪控制方法进行了测试,系统仿真和试验结果证明该方法是可行的。 展开更多
关键词 开关磁阻发电机 风力发电 最大风能跟踪 可变步长
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Dynamic modeling and direct power control of wind turbine driven DFIG under unbalanced network voltage conditions 被引量:2
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作者 Jia-bing HU Yi-kang HE lie xu 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2008年第12期1731-1740,共10页
This paper proposes an analysis and a direct power control (DPC) design of a wind turbine driven doubly-fed induction generator (DFIG) under unbalanced network voltage conditions. A DFIG model described in the positiv... This paper proposes an analysis and a direct power control (DPC) design of a wind turbine driven doubly-fed induction generator (DFIG) under unbalanced network voltage conditions. A DFIG model described in the positive and negative synchronous reference frames is presented. Variations of the stator output active and reactive powers are fully deduced in the presence of negative sequence supply voltage and rotor flux. An enhanced DPC scheme is proposed to eliminate stator active power oscillation during network unbalance. The proposed control scheme removes rotor current regulators and the decomposition processing of positive and negative sequence rotor currents. Simulation results using PSCAD/EMTDC are presented on a 2-MW DFIG wind power generation system to validate the feasibility of the proposed control scheme under balanced and unbalanced network conditions. 展开更多
关键词 Doubly-fed induction generator (DFIG) Wind turbine Direct power control (DPC) Stator voltage oriented (SVO) Unbalanced network
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Numerical and experimental study on coke size distribution in bell-type charging in the CDQ shaft 被引量:2
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作者 Zhicheng Liu Yanhui Feng +2 位作者 Xinxin Zhang lie xu Zhendong Yu 《Journal of University of Science and Technology Beijing》 CSCD 2008年第3期236-240,共5页
The mechanism of coke size segregation in the radial direction of pre-chamber in coke dry quenching (CDQ) shaft was investigated by experiment and numerical analysis. The experimental apparatus was a cold three-dime... The mechanism of coke size segregation in the radial direction of pre-chamber in coke dry quenching (CDQ) shaft was investigated by experiment and numerical analysis. The experimental apparatus was a cold three-dimensional semicircle model for bell-type charging, which was used to study the influences of different kinds of bells and different stock line levels on the radial distribution of coke size in the radial direction of a pre-chamber. A mathematical model was used, which is capable of estimating the radial average size distribution as well as the radial deposit distribution of each particle size for multiple size coke with a few fixed parameters. The calculated results agree well with the experimental data, which proves the reliability of both experimental study and numerical analysis. 展开更多
关键词 COKE size distribution coke dry quenching (CDQ) size segregation CHARGING
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Operation of offshore wind farms connected with DRU-HVDC transmission systems with special consideration of faults 被引量:4
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作者 Rui Li Lujie Yu lie xu 《Global Energy Interconnection》 2018年第5期608-617,共10页
The diode rectifier unit(DRU)-based high-voltage DC(DRU-HVDC) system is a promising solution for offshore wind energy transmission thanks to its compact design, high efficiency, and strong reliability. Herein we inves... The diode rectifier unit(DRU)-based high-voltage DC(DRU-HVDC) system is a promising solution for offshore wind energy transmission thanks to its compact design, high efficiency, and strong reliability. Herein we investigate the feasibility of the DRU-HVDC system considering onshore and offshore AC grid faults, DC cable faults, and internal DRU faults. To ensure safe operation during the faults, the wind turbine(WT) converters are designed to operate in either current-limiting or voltage-limiting mode to limit potential excessive overcurrent or overvoltage. Strategies for providing fault currents using WT converters during offshore AC faults to enable offshore overcurrent and differential fault protection are investigated. The DRU-HVDC system is robust against various faults, and it can automatically restore power transmission after fault isolation. Simulation results confirm the system performance under various fault conditions. 展开更多
关键词 DIODE RECTIFIER unit(DRU) Fault protection HVDC transmission Offshore wind FARM
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Effects of Region and Elevation on Adaptation of Leaf Functional Traits of an Invasive Plant Erigeron annuus in China
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作者 Yuanyuan Liu Zhen Li +2 位作者 lie xu Qiang Fu Yongjian Wang 《Phyton-International Journal of Experimental Botany》 SCIE 2022年第1期115-128,共14页
A key scientific challenge relating to the threat of invasive plants on agriculture at the region level is to understand their adaptation and evolution in functional traits.Leaf functional traits,related to growth and... A key scientific challenge relating to the threat of invasive plants on agriculture at the region level is to understand their adaptation and evolution in functional traits.Leaf functional traits,related to growth and resource utilization,might lead to adaptation of invasive plants to the geographical barriers(region or elevation).In the field experiment,we discussed the effects of region and elevation on leaf functional traits on invasive plant Erigeron annuus in farmland habitats in China.We compared leaf size,coefficient of variation(CV)of leaf traits,and fluctuating asymmetry(FA)of E.annuus from three regions(east vs.center vs.west)and two leaf types(vegetative vs.reproductive leaf),and from nine elevations(980-2100 m)in the west region of China.Our results indicated region and leaf type influenced leaf functional traits,and leaf size was significantly higher and CV of leaf traits and FA in reproductive leaves were significantly lower in the east region than in the west and center regions.Elevation and leaf type affected leaf functional traits,and leaf size was significantly higher and CV of leaf traits in reproductive leaves were significantly lower in moderate elevation.E.annuus has higher leaf size and developmental stability(lower CV and FA)in the eastern region due to the longer adaptation period.Therefore,leaf functional traits play an important role in the adaptation of different longitudes and elevations.It can also facilitate the understanding of the invasiveness and adaptation of leaf traits of invasive plants in the agricultural ecosystem during their spread process in China. 展开更多
关键词 Invasive alien plants(IAS) leaf traits coefficient of variation fluctuating asymmetry developmental stability
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Proportional integral plus multi-frequency resonant current controller for grid-connected voltage source converter under imbalanced and distorted supply voltage conditions 被引量:15
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作者 Jia-bing HU Wei ZHANG +2 位作者 Hong-sheng WANG Yi-kang HE lie xu 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2009年第10期1532-1540,共9页
This paper proposes a current control scheme for a grid-connected pulse width modulator(PWM) voltage source converter(GC-VSC) under imbalanced and distorted supply voltage conditions.The control scheme is implemented ... This paper proposes a current control scheme for a grid-connected pulse width modulator(PWM) voltage source converter(GC-VSC) under imbalanced and distorted supply voltage conditions.The control scheme is implemented in the positive synchronously rotating reference frame and composed of a single proportional integral(PI) regulator and multi-frequency resonant controllers tuned at the frequencies of 2ω and 6ω,respectively.The experimental results,with the target of eliminating the active power oscillations and current harmonics on a prototype GC-VSC system,validate the feasibility of the proposed current control scheme during supply voltage imbalance and distortion. 展开更多
关键词 Grid-connected voltage source converter (GC-VSC) Proportional integral plus multi-frequency resonant (PI+MFR) IMBALANCE Harmonics distortion
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Wind turbines output power smoothing using embedded energy storage systems 被引量:7
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作者 Guoyi xu lie xu Liangzhong YAO 《Journal of Modern Power Systems and Clean Energy》 SCIE EI 2013年第1期49-57,共9页
The ability of an energy storage system to improve the performance of a wind turbine(WT)with a fully rated converter was evaluated,where the energy storage device is embedded in the direct current(dc)link with a bidir... The ability of an energy storage system to improve the performance of a wind turbine(WT)with a fully rated converter was evaluated,where the energy storage device is embedded in the direct current(dc)link with a bidirectional dc/dc converter.Coordinated dc voltage control design of the line-side converter and the energy storage dc/dc converters was proposed using a common dc voltage measurement for smoothing the output power.A transfer function and Bode diagram were introduced to analyze the system performance with different control parameters.MATLAB/Simulink simulations are presented to demonstrate the effectiveness of the proposed methods.It was found that the proposed methods smooth the power output from the WT to the grid and thus improve the quality of the generated power. 展开更多
关键词 Direct current voltage control Energy storage system Power smoothing Wind turbine
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Protection of large partitioned MTDC Networks Using DC-DC converters and circuit breakers 被引量:10
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作者 Md Habibur Rahman lie xu Liangzhong Yao 《Protection and Control of Modern Power Systems》 2016年第1期170-178,共9页
This paper proposes a DC fault protection strategy for large multi-terminal HVDC(MTDC)network where MMC based DC-DC converter is configured at strategic locations to allow the large MTDC network to be operated interco... This paper proposes a DC fault protection strategy for large multi-terminal HVDC(MTDC)network where MMC based DC-DC converter is configured at strategic locations to allow the large MTDC network to be operated interconnected but partitioned into islanded DC network zones following faults.Each DC network zone is protected using either AC circuit breakers coordinated with DC switches or slow mechanical type DC circuit breakers to minimize the capital cost.In case of a DC fault event,DC-DC converters which have inherent DC fault isolation capability provide‘firewall’between the faulty and healthy zones such that the faulty DC network zone can be quickly isolated from the remaining of the MTDC network to allow the healthy DC network zones to remain operational.The validity of the proposed protection arrangement is confirmed using MATLAB/SIMULINK simulations. 展开更多
关键词 DC circuit breaker DC-DC converter DC fault HVDC Modular multilevel converter(MMC) Network
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Computational and Experimental Study of Cooling Process in Coke Dry Quenching Experimental Shaft 被引量:2
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作者 Huafei Liu Xinxin Zhang +5 位作者 Maolin Wu Yanhui Feng Yingbo Wang Dinan Wang lie xu Wenghua Zheng 《Journal of Thermal Science》 SCIE EI CAS CSCD 2002年第2期121-127,共7页
Owing to its merits in energy savings, environmental protection and coke quality improvement, the Coke Dry Quenching (CDQ) technology is favorite in coke making industry today. In order to validate the mathematical mo... Owing to its merits in energy savings, environmental protection and coke quality improvement, the Coke Dry Quenching (CDQ) technology is favorite in coke making industry today. In order to validate the mathematical model developed for the cooling process of real CDQ shaft, the one-seventh scale experimental setup was established. With the air as the working fluid and the coke as the packed bed, the coke and gas temperatures and the pressure drop in the cooling shaft were measured. A mathematical model based on the non-Darcian and non-thermal equilibrium model for the cooling process of the CDQ experimental shaft was presented. The computational results were compared to the experimental data. It was found that most numerical predictions were supported by the measured values. 展开更多
关键词 COMPUTATIONAL and EXPERIMENTAL study cooling process COKE dry QUENCHING (CDQ)
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Mathematical Model for Fluid Flow and Heat Transfer in the Cooling Shaft of Coke Dry Quenching Unit 被引量:2
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作者 Huafei Liu Xinxin Zhang +1 位作者 lie xu Mingdeng Wang 《Journal of Thermal Science》 SCIE EI CAS CSCD 2002年第1期65-73,共9页
A mathematical model based on non-Darcian flow and two-phase model is developed for fluid flow and heat transfer in the cooling shaft of Coke Dry Quenching (CDQ) unit. The potential flow model is employed to simulate ... A mathematical model based on non-Darcian flow and two-phase model is developed for fluid flow and heat transfer in the cooling shaft of Coke Dry Quenching (CDQ) unit. The potential flow model is employed to simulate coke descending. Governing equations are solved by the SIMPLE algorithm on the collocated, non-orthogonal and body-fitted grids. The velocity of circulating gas and the temperature of coke and gas are obtained to study the effects of coke size distribution on flow and heat transfer behavior in the cooling shaft. It is found that the non-uniformity of gas velocity and the unevenness of coke temperature in the radial direction can be reduced if coke size distribution is improved. The gas velocity field and the temperature distribution of coke and gas are presented. 展开更多
关键词 coke dry quenching(CDQ) porous media non-Darcian flow two-phase model non-orthogonal grid
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Nucleate pool boiling heat transfer measurements of HFC23/CFC13 system
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作者 Liqiang ZHANG Maoqiong GONG +1 位作者 Jianfeng WU lie xu 《Journal of Thermal Science》 SCIE EI CAS CSCD 2007年第4期370-375,共6页
Nucleate pool boiling heat transfer data of the HFC23/CFC13 system have been systematically measured in a wide range of pressures and heat fluxes. The experimental results are also compared with the measured data of R... Nucleate pool boiling heat transfer data of the HFC23/CFC13 system have been systematically measured in a wide range of pressures and heat fluxes. The experimental results are also compared with the measured data of R508A and R508B. It is found that the heat transfer coefficient of R503 (HFC23/CFC13=0.511/0.489) is higher than that of R508A and R508B. Furthermore, the measured data were compared with the predicted results with three well-known correlations. Correlation by Fujita and Tsutsui can provide acceptable results. Most of the data fall within ±20% of this correlation. 展开更多
关键词 heat transfer pool boiling azeotropic system refrigerant mixtures.
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