双馈感应风力发电机三相短路电流分析与仿真研究

基于DFIG精确暂态数学模型,深入研究了机端三相短路所激起的双馈电机电磁过渡过程产生的机理及定、转子电流中各频率成分之间的依存关系,并详细推导了三相短路电流的解析表达式, 在此基础上,深入分析了定子和转子绕组阻值对短路电流幅值的影响规律,得到抑制短路电流最佳阻值,实际仿真验证了分析结论的有效性。此研究对于深入探索风机crowbar保护的电阻值整定及短路电流抑制措施都有十分重要的意义。     

双馈感应发电机风电机组的动态模型构建

双馈感应发电机(DFIG)动态模型用于反映发生扰动时风电机组的动态特性变化,是研究DFIG并网稳定性的重要基础。通过建立DFIG风机的空气动力学模型、桨距角控制模型、发电机模型、轴系模型、变流器及其控制模型在内的动态模型,分析了各部分模型的控制机理,并且给出了各部分的控制框图,在PSCAD中对DFIG并网模型进行了仿真研究,证实了DFIG动态模型是正确可信的。     

双馈风电机组接入地区电网后的电压稳定分析

利用PSASP软件的UPI接口程序模块．在PSASP中建立了双馈风电机组模型,以两个实际的地区电网为例,研究双馈风电机组接入地区电网后对电网电压的影响,结果表明：双馈风电机组提高了地区电网的静态电压水平：双馈风电机组在故障后能够减少系统所需的无功储备,从而有利于地区电网的电压稳定;风速的波动对地区电网的电压有影响,但一般不会影响其暂态稳定性。     

Microgrid Dynamic Performance Improvement Using a Doubly Fed Induction Wind Generator

This paper describes a control approach applied on a doubly fed induction generator (DFIG) to provide both voltage and frequency regulation capabilities, and hence, an improvement in the dynamic behavior of a microgrid system. The microgrid system is assumed to be a portion of a medium voltage distribution feeder and is supplied by two distributed generation (DG) units, i.e., a gas-turbine synchronous generator and a variable-speed wind turbine with DFIG. A control approach algorithm is proposed for the DFIG unit to improve both voltage and primary frequency controls. Two distinct operation modes, i.e., grid-connected and islanding mode, are used in the proposed approach for proper transfer from normal to islanding operation. Case studies are simulated based on both planned and unplanned islanding scenarios to evaluate the performance of the control approach. The study results show that the proposed control approach for DGs in the microgrid increase the microgrid system's dynamic performance, reduce frequency changes, and improve bus voltages regulation during islanding and autonomous operations.      

Control of a Doubly Fed Induction Wind Generator Under Unbalanced Grid Voltage Conditions

Wind energy is often installed in rural, remote areas characterized by weak, unbalanced power transmission grids. In induction wind generators, unbalanced three-phase stator voltages cause a number of problems, such as overcurrent, unbalanced currents, reactive power pulsations, and stress on the mechanical components from torque pulsations. Therefore, beyond a certain amount of unbalance, induction wind generators are switched out of the network. This can further weaken the grid. In doubly fed induction generators (DFIGs), control of the rotor currents allows for adjustable speed operation and reactive power control. This paper presents a DFIG control strategy that enhances the standard speed and reactive power control with controllers that can compensate for the problems caused by an unbalanced grid by balancing the stator currents and eliminating torque and reactive power pulsations     

双馈异步风电系统的建模仿真

当电网电压跌落时,风电机组须维持一定时间与电网连接而不解列,并且能提供无功以支持电网电压的恢复,即具有低电压穿越能力,而双馈风电机组低电压穿越能力最弱。分析建立了双馈风力发电机组的模型,通过使用MATLAB/SIMULINK仿真,来研究它的LVRT性能,及影响它LVRT性能的因素,探讨它的改进方案。     

滞环矢量控制在双馈风力发电机中的应用

滞环电流控制方法以其动态响应速度快,电路跟踪性能好的优点而获得了广泛的应用和发展。基于双馈发电机数学模型,采用定子磁场定向的矢量控制．转子侧选用改进型滞环电流控制,建立了有功功率、无功功率解耦的控制策略。利用PSCAD软件．建立了仿真控制模型并进行了仿真计算。仿真结果表明,该控制系统能有效地实现双馈发电机有功、无功功率的解耦,验证该控制方案的正确性和有效性。     

应用SVC提高双馈感应发电机并网的风电场暂态电压稳定性

摘要： 采用SVC改善双馈感应型风电场并网时暂态电压稳定性。通过仿真软件DIgSILENT/Power Factory建立静止无功补偿器（SVC）的控制模型。以实现风电场的低电压穿越（low voltage ride through,LVRT）的前提下应用SVC改善风电场的电压稳定性。仿真结果表明,采用SVC的并网风电场具有良好的动态性能,并且提高了风电机组在系统出现故障时的LVRT能力,确保了风电机组的连续运行和电网的安全稳定。     

改善基于双馈感应发电机并网风电场的低电压穿越能力研究

为保持系统稳定,必须要求大规模并网风电场具有低电压穿越能力。双馈感应发电机（DFIG）低电压穿越功能已成为研究热点。介绍了串联制动电阻装置对双馈感应发电机暂稳特性贡献的机理。详细分析了在电网故障情况下,制动电阻装置对双馈风电场低电压穿越能力的贡献,分别就制动电阻接在风电场升压变处与接在双馈感应发电机机端对低电压穿越的改善效果进行分析。试验结果表明：故障期间投入适当大小制动电阻,能较好地提高双馈风电场低电压穿越功能;将制动电阻放置在风电场升压变处贡献效果优于将制动电阻装置放置在双馈感应发电机机端处。     

Performance Study of a Doubly Fed Wind-Power Induction Generator Under Network Disturbances

Transient performance of a 1.7-MW wind-power doubly fed induction generator (DFIG) under network disturbances is studied using a coupled field-circuit simulator. The simulator consists of the finite-element method model of a DFIG coupled with the circuit model of the frequency converter, a transformer, and a simple model of the network. The simulation results show the transient behavior of the DFIG when a sudden voltage dip is introduced. The field-circuit simulator is experimentally validated by full-power measurement     

Dynamic Behavior of the Doubly Fed Induction Generator During Three-Phase Voltage Dips

The use of doubly fed induction generators (DFIGs) in large wind turbines has become quite common over the last few years. These machines provide variable speed and are driven with a power converter which is sized for a small percentage of the turbine-rated power. A drawback of the DFIG is that it is very sensitive to grid disturbances, especially to voltage dips. However, the operation of the machine in these situations has only been studied in the literature by means of simulations. This paper develops a theoretical analysis of the dynamic behavior of the induction machine during three-phase voltage dips. The proposed analysis contributes to understanding the causes of the problem and represents a very useful tool to improve the existing solutions and propose new alternatives. Experimental results are in good agreement with those obtained theoretically and validate the proposed analysis.     

Ride-Through Control of a Doubly Fed Induction Generator Under Unbalanced Voltage Sags

This paper deals with the control of doubly fed induction generators to ride through unbalanced voltage sags. A control strategy is proposed by choosing certain current reference values in the positive and negative sequences so that the torque and the dc voltage are kept stable during such unbalanced sags. Both rotor- and grid-side converters are considered, detailing the control scheme of each converter while considering the effect of the crowbar protection. The control strategy is validated by means of simulations.      

双馈风力发电机的频率控制策略研究

提出了双馈风电机组参加频率控制的2种控制策略,惯性控制策略和下降速率控制策略,建立了2种控制策略下的双馈机组的控制器模型.为充分发挥双馈发电机和常规发电机的快速功率调节能力,下降速率控制策略采用冲失滤波器提取频率变化的高频信号做为双馈发电机的频率输入信号,并对双馈机组的控制参数提出了基于ISE优化设计方法.建立了含风电机组的两区域AGC控制系统模式,进行了负荷扰动仿真,对2种控制策略下的系统动态性能进行了比较.仿真结果表明,基于下降速率的控制策略可以使双馈风电机组在频率调节中充分发挥有功调节作用.     

Modal Analysis of Grid-Connected Doubly Fed Induction Generators

This paper presents the modal analysis of a grid-connected doubly fed induction generator (DFIG). The change in modal properties for different system parameters, operating points, and grid strengths are computed and observed. The results offer a better understanding of the DFIG intrinsic dynamics, which can also be useful for control design and model justification.     

Contribution of Doubly Fed Wind Generators to Oscillation Damping

In this paper, the effects of increased wind power penetration by doubly fed asynchronous generators (DFAGs) on oscillation damping are investigated. With the help of an illustrative example, it is shown that the general trend for DFAGs is to increase interarea oscillation damping. However, there are exceptions for certain penetration levels (not necessarily large), for which the voltage control (VC) option of DFAGs can reduce damping. It is also shown that the modulation of active power generation of wind turbines is a powerful tool to introduce additional damping to interarea oscillations through a simple wind power system stabilizer design. The general trend for increased oscillation damping is verified in the case of a large interconnected system encompassing Southeastern Europe for a projected high level of wind penetration in Greece. For the same system, it is also shown that low-damping voltage oscillations possibly introduced by the VC mode of DFAGs can be adequately damped by properly adjusting control parameters.      

基于混合储能DVR的双馈式风电机组故障穿越能力研究

针对2 MW的双馈式风电机组(DFIG)的电网故障问题,提出了蓄电池与超级电容器混合储能的动态电压恢复器(DVR),以提高DFIG的故障穿越能力。在电网电压故障时,可对机组端口电压进行完全补偿,使风电机组的定子电压、转子电流和直流侧电压维持在正常水平。在Matlab/Simulink环境中建立DFIG-DVR系统仿真模型,进行了对称和不对称故障下的低电压穿越和对称故障下的高电压穿越仿真,仿真结果表明混合储能DVR可有效提升风电机组的故障穿越能力。     

双馈变速风电机组低电压穿越控制

当系统中风电装机容量比例较大时,系统故障导致电压跌落后,风电场切除会严重影响系统运行的稳定性,这就要求风电机组具有低电压穿越（Low Voltage Ride Through,LVRT）能力,保证系统发生故障后风电机组不间断并网运行。分析了双馈风电机组LVRT原理和基于转子撬棒保护（crow-bar protection）的LVRT控制策略,在电力系统仿真分析软件DIgSILENT/Power Factory中建立了双馈风电机组模型及其LVRT控制模型,以某地区风电系统为例进行仿真计算,分析转子撬棒投入与切除策略及动作时间对实现机组LVRT的影响。     

考虑低电压穿越影响的双馈感应 发电机谐波电流特性

双馈感应发电机（DFIG）作为当前应用最广泛的风力发电机,其特殊的结构使其故障运行特性十分复杂,尤其在低电压穿越（LVRT）运行状态下,已对电网安全运行和保护控制的顺利实施造成一系列影响。目前对DFIG的短路电流特性已有大量研究,但是针对定转子电流谐波特性的研究还鲜有报道。考虑LVRT的影响,对电网不对称故障情况下DFIG定、转子谐波电流的特性进行研究。从电磁暂态过程的角度详细推导了Crowbar动作后的DFIG定子谐波电流的解析表达式;在Crowbar未动作时,从转子侧变流器影响机理出发,研究了由变流器控制引起的定、转子谐波电流的产生机理。所得结论通过仿真进行了验证     

基于双环控制的双馈风力发电机组控制策略

在分析了双馈风力发电机组运行特性的基础上,提出一种基于双环控制的变换器控制策略。在转子侧,变换器采用定子磁链定向矢量控制技术,推导出了用转子有功电流和无功电流独立解耦控制有功功率和无功功率的策略,并实现了风能的最大跟踪;在电网侧,变换器采用电网电压定向矢量控制技术,构建了电流内环、电压外环的双闭环PI控制系统。利用PSCAD/EMTDC软件,构建了双馈风力发电机组仿真模型。仿真结果验证了所提控制策略的有效性和合理性     

含双馈感应风电机组的配电网无功优化

考虑传统无功调节设备调节次数限制和双馈感应电机无功容量限制等约束条件,提出一种基于双馈感应电机与传统无功调节设备协调控制的分时段分层无功优化策略。首先,该策略采用谱系聚类算法对预测等效负荷曲线进行分段;其次,在每个时段采用分层调控策略进行无功优化,建立以网损和平均电压偏离度之和为目标函数的无功优化模型,上层利用改进粒子群算法计算出包括双馈感应机组在内的各种无功调节设备的优化运行状态,并预先对变压器、电容器动作;在此基础上,下层利用双馈感应机组的无功调节能力对上层优化得出的并网点电压进行自动跟踪控制,由此实现了每个时段内接入点电压控制和全局无功优化相结合,最后以IEEE33节点配电系统为算例来验证上述策略的有效性。