In this paper, a practical method to establish Doubly Fed Induction Generator (DFIG) based wind farm equivalent model for switching transient analysis is demonstrated. In order to verify this method, a 3.6MW equivalen...In this paper, a practical method to establish Doubly Fed Induction Generator (DFIG) based wind farm equivalent model for switching transient analysis is demonstrated. In order to verify this method, a 3.6MW equivalent wind farm model is built. The steady state results and load switching results are verified with those of detailed models of four 0.9MW generators. Using this method, a model of 40MW wind farm, representing the capacity for a proposed South Carolina offshore wind farm is established. To study large wind farm switching transient impacts on a system, different switching operations such as cable energizing and three phase faults at different locations in wind farm are investigated and their impact on system are analysed. Finally, conclusions based on the switching cases are presented.展开更多
The aim of this paper is to analyze the potential of switched reluctance generator (SRG) in wind energy application. The machine comprises of switched reluctance generator, power converter and controller. In this pape...The aim of this paper is to analyze the potential of switched reluctance generator (SRG) in wind energy application. The machine comprises of switched reluctance generator, power converter and controller. In this paper the main ele-ments that form the generator system is discussed. It also highlights the common type of converter and structure used for SRG in wind energy application and types of control strategy available. Using power converter for switching the generator can operate over a wide speed range. Its applications in high speed area such as starter/generator for air-craft and gas turbine has been established, however the low/medium speed operation is still at an early stage of re-search. In order to subject the machine to various parameters, offline modeling is being investigated to produce the best optimum design.展开更多
This research work seeks to make renewable energy more reliable, cost effective, and accessible by exploring a different energy combination system to that currently applied to wind and hydro power. Instead of the usua...This research work seeks to make renewable energy more reliable, cost effective, and accessible by exploring a different energy combination system to that currently applied to wind and hydro power. Instead of the usual electrical combination of wind and hydro generators, this work involved combining a water and wind turbine mechanically, before driving an electrical generator. This new combination system was modeled and optimized in MATLAB, using a direct combination system commonly found in multi-engine helicopters. The system was found to operate satisfactorily, however it is mechanically more complex than current electrical combining systems. Research was undertaken regarding wind and water resource availability, and the turbines were chosen with these taken into consideration. Various combination systems were explored, including torque and speed split mechanical combinations, conventional electrical combination, and using a modified switched reluctance generator as a method of electro-mechanical combination. The generator selected for this work is a three phase 12/8 Switched Reluctance (SR) machine. A detailed winding polarity having four poles per phase and their effect on the performance of the machine is展开更多
This paper deals with various aspects of modeling, simulation, analysis, and control ofa SRG （switched reluctance generator） in different modes of operation. Excitation method of such a generator is shortly describe...This paper deals with various aspects of modeling, simulation, analysis, and control ofa SRG （switched reluctance generator） in different modes of operation. Excitation method of such a generator is shortly described. The output power of the SRG is controlled so that it can track the maximum output power of a wind turbine drive applications. Also, the output generator voltage is stabilized under either load or wind speed variations. Basic operational characteristics of a three-phase 6/4 SRG are developed through experimental observation. Meanwhile, the real-time operation was implemented in a DSP （digital signal processor） environment. The simulation of the complete system model has been obtained using the Matlab/Simulink software. A good agreement between experimental and simulation results has been observed which supports the validity of the proposed analysis.展开更多
Heat and thermal problems are major obstacles to achieving high power density in compact permanent magnet(PM)topologies.Consequently,a comprehensive,accurate,and rapid temperature rise estimation method is required fo...Heat and thermal problems are major obstacles to achieving high power density in compact permanent magnet(PM)topologies.Consequently,a comprehensive,accurate,and rapid temperature rise estimation method is required for novel electric machines to ensure safe and reliable operations.A unique three-dimensional(3D)lumped parameter thermal network(LPTN)is presented for accurate thermal modeling of a newly developed outer-rotor hybrid-PM flux switching generator(OR-HPMFSG)for direct-drive applications.First,the losses of the OR-HPMFSG are calculated using 3D finite element analysis(FEA).Subsequently,all machine components considering the thermal contact resistance,anisotropic thermal conductivity of materials,and various heat flow paths are comprehensively modeled based on the thermal resistances.In the proposed 3-D LPTN,internal nodes are considered to predict the average temperature as well as the hot spots of all active and passive components.Experimental measurements are performed on a prototype OR-HPMFSG to validate the efficiency of the 3-D LPTN.A comparison of the results at various operating points between the developed 3-D LPTN,experimental test,and FEA indicates that the 3-D LPTN quickly approximates the hotspot and mean temperature of all components under both transient and steady states with high accuracy.展开更多
海上风电场需具备低电压穿越(low voltage ride-through,LVRT)能力,以避免故障时风机脱网,然而,LVRT策略对并网系统大扰动后的稳定性影响不明。有鉴于此,该文搭建了接入交流电网系统的海上直驱风电场模型,并分析其在弱连接时大扰动下LVR...海上风电场需具备低电压穿越(low voltage ride-through,LVRT)能力,以避免故障时风机脱网,然而,LVRT策略对并网系统大扰动后的稳定性影响不明。有鉴于此,该文搭建了接入交流电网系统的海上直驱风电场模型,并分析其在弱连接时大扰动下LVRT引发的不同类型振荡机理和特性。具体如下:首先搭建了含LVRT的海上直驱风电场接入交流电网系统电磁暂态模型;其次,分析了该系统的阻抗特性,发现该系统具有次同步振荡风险,且在弱连接时正阻尼系统遭受大扰动后会出现LVRT参与形成的次同步频段振荡;再次,探究了振荡和LVRT不同控制环节的关系,表明大扰动后正阻尼系统的LVRT无功环节阶段2-1的策略1或2均可参与形成因补偿电流过大而引发的切换型振荡,且不同控制策略对应的振荡均存在限幅间歇性饱和现象;最后,分析了LVRT控制策略及参数对振荡特性的影响。展开更多
文摘In this paper, a practical method to establish Doubly Fed Induction Generator (DFIG) based wind farm equivalent model for switching transient analysis is demonstrated. In order to verify this method, a 3.6MW equivalent wind farm model is built. The steady state results and load switching results are verified with those of detailed models of four 0.9MW generators. Using this method, a model of 40MW wind farm, representing the capacity for a proposed South Carolina offshore wind farm is established. To study large wind farm switching transient impacts on a system, different switching operations such as cable energizing and three phase faults at different locations in wind farm are investigated and their impact on system are analysed. Finally, conclusions based on the switching cases are presented.
文摘The aim of this paper is to analyze the potential of switched reluctance generator (SRG) in wind energy application. The machine comprises of switched reluctance generator, power converter and controller. In this paper the main ele-ments that form the generator system is discussed. It also highlights the common type of converter and structure used for SRG in wind energy application and types of control strategy available. Using power converter for switching the generator can operate over a wide speed range. Its applications in high speed area such as starter/generator for air-craft and gas turbine has been established, however the low/medium speed operation is still at an early stage of re-search. In order to subject the machine to various parameters, offline modeling is being investigated to produce the best optimum design.
文摘This research work seeks to make renewable energy more reliable, cost effective, and accessible by exploring a different energy combination system to that currently applied to wind and hydro power. Instead of the usual electrical combination of wind and hydro generators, this work involved combining a water and wind turbine mechanically, before driving an electrical generator. This new combination system was modeled and optimized in MATLAB, using a direct combination system commonly found in multi-engine helicopters. The system was found to operate satisfactorily, however it is mechanically more complex than current electrical combining systems. Research was undertaken regarding wind and water resource availability, and the turbines were chosen with these taken into consideration. Various combination systems were explored, including torque and speed split mechanical combinations, conventional electrical combination, and using a modified switched reluctance generator as a method of electro-mechanical combination. The generator selected for this work is a three phase 12/8 Switched Reluctance (SR) machine. A detailed winding polarity having four poles per phase and their effect on the performance of the machine is
文摘This paper deals with various aspects of modeling, simulation, analysis, and control ofa SRG （switched reluctance generator） in different modes of operation. Excitation method of such a generator is shortly described. The output power of the SRG is controlled so that it can track the maximum output power of a wind turbine drive applications. Also, the output generator voltage is stabilized under either load or wind speed variations. Basic operational characteristics of a three-phase 6/4 SRG are developed through experimental observation. Meanwhile, the real-time operation was implemented in a DSP （digital signal processor） environment. The simulation of the complete system model has been obtained using the Matlab/Simulink software. A good agreement between experimental and simulation results has been observed which supports the validity of the proposed analysis.
文摘Heat and thermal problems are major obstacles to achieving high power density in compact permanent magnet(PM)topologies.Consequently,a comprehensive,accurate,and rapid temperature rise estimation method is required for novel electric machines to ensure safe and reliable operations.A unique three-dimensional(3D)lumped parameter thermal network(LPTN)is presented for accurate thermal modeling of a newly developed outer-rotor hybrid-PM flux switching generator(OR-HPMFSG)for direct-drive applications.First,the losses of the OR-HPMFSG are calculated using 3D finite element analysis(FEA).Subsequently,all machine components considering the thermal contact resistance,anisotropic thermal conductivity of materials,and various heat flow paths are comprehensively modeled based on the thermal resistances.In the proposed 3-D LPTN,internal nodes are considered to predict the average temperature as well as the hot spots of all active and passive components.Experimental measurements are performed on a prototype OR-HPMFSG to validate the efficiency of the 3-D LPTN.A comparison of the results at various operating points between the developed 3-D LPTN,experimental test,and FEA indicates that the 3-D LPTN quickly approximates the hotspot and mean temperature of all components under both transient and steady states with high accuracy.
文摘海上风电场需具备低电压穿越(low voltage ride-through,LVRT)能力,以避免故障时风机脱网,然而,LVRT策略对并网系统大扰动后的稳定性影响不明。有鉴于此,该文搭建了接入交流电网系统的海上直驱风电场模型,并分析其在弱连接时大扰动下LVRT引发的不同类型振荡机理和特性。具体如下:首先搭建了含LVRT的海上直驱风电场接入交流电网系统电磁暂态模型;其次,分析了该系统的阻抗特性,发现该系统具有次同步振荡风险,且在弱连接时正阻尼系统遭受大扰动后会出现LVRT参与形成的次同步频段振荡;再次,探究了振荡和LVRT不同控制环节的关系,表明大扰动后正阻尼系统的LVRT无功环节阶段2-1的策略1或2均可参与形成因补偿电流过大而引发的切换型振荡,且不同控制策略对应的振荡均存在限幅间歇性饱和现象;最后,分析了LVRT控制策略及参数对振荡特性的影响。
