双馈风力发电机组等效模型对机组暂态稳定性影响

为研究并网双馈风力发电机组的机电耦合作用对机组暂态性能的影响,采用等效集中质量法,在Mat-lab/Simulink环境下,提出一种基于叶片弯曲柔性和传动轴扭转柔性的风力发电机组3质量块等效模型。结合双馈发电机控制策略,分别以额定功率750 kW和3 MW的风力发电机组为例,对其在电网电压跌落和机械扰动两种情况下进行暂态稳定性仿真,并将仿真结果和传统的1质量块、2质量块等效模型的仿真结果进行比较分析。结果表明:随着单机容量的增加,叶片的柔性对机组暂态稳定性的影响逐渐增大,建立3质量块等效模型对研究大容量双馈风力发电机组暂态稳定性是必要和有效的。     

Analysis and estimation of transient stability for a grid-connected wind turbine with induction generator

Increasing levels of wind energy in modern electrical power system is initiating a need for accurate analysis and estimation of transient stability of wind turbine generation systems. This paper investigates the transient behaviors and possible direct methods for transient stability evaluation of a grid-connected wind turbine with squirrel cage induction generator (SCIG). Firstly, by using an equivalent lump mass method, a three-mass wind turbine equivalent model is proposed considering both the blades and the shaft flexibility of the wind turbine drive train system. Combined with the detailed electromagnetic transient models of a SCIG, the transient behaviors of the wind turbine generation system during a three-phase fault are simulated and compared with the traditional models. Secondly, in order to quickly estimate the transient stability limit of the wind turbine generation system, a direct method based on normal form theory is proposed. The transient models of the wind turbine generation system including the flexible drive train model are derived based on the direct transient stability estimation method. A method of critical clearing time (CCT) calculation is developed for the transient stability estimation of the wind turbine generation system. Finally, the CCT at various initial mechanical torques for different dynamical models are calculated and compared with the trial and error method by simulation, when the SCIG stator terminal is subjected to a three-phase short-circuit fault. The results have shown the proposed method and models are correct and valid.     

传动链模型对风机低电压穿越能力的影响

电网电压跌落故障时风电机组应能保持与电网连接并向系统不间断供电,根据风电机组在暂态过程中的表现提出低电压穿越(LVRT)要求。考虑传动轴扭转柔性因素,应用等效质量法,建立了变速恒频风电系统传动链的一质量块等效模型和二质量块等效模型。当发生电网电压跌落故障时,对采用不同传动链模型的风电系统进行仿真比较及理论分析。     

Drive train dynamics assessment and speed controller design in variable speed wind turbines

This paper deals with the speed controller design in DFIG based wind turbines, and investigates stability and performance of the drive train dynamics against different control strategies. It is shown that speed controller design based on the single mass drive train model may result in unstable mechanical modes, because it ignores the dynamics of the flexible shaft. Then, another control approach, known as feedforward compensation of the shaft torsional torque, is examined. It is shown that this control method results in poorly damped oscillations of torsional torque and turbine speed during the transient conditions. The open loop transfer function from the electromagnetic torque to the generator speed contains a dual quadratic function representing the dynamics of flexible shaft. The dual quadratic function comprises resonant and anti-resonant frequencies that greatly affect the stability of the drive train dynamics. Next, a step-by-step procedure for designing the speed controller based on the two-mass drive train model is proposed. The proposed speed controller provides stable closed loop system, zero tracking error, low-frequency disturbance rejection, and open-loop gain attenuation at the resonant frequency. At the end, performance of the proposed controller is investigated by the time domain simulations.     

考虑磁路饱和及集肤效应的异步风力发电机组暂态性能分析

为准确分析异步发电机不同详细模型对大型风电机组暂态性能的影响,该文结合2个质量块的风力机传动链等效模型,分别建立了笼型异步发电机考虑主磁路、定转子漏磁路饱和以及集肤效应影响的风电机组数学模型。针对大型风电机组在机械大扰动和电网电压骤降情况下,利用Matlab/Simulink平台对机组在不同数学模型描述时的暂态过程进行了仿真比较。结果表明,尤其在电网电压骤降时,电机磁路饱和对机组暂态运行性能的影响较为显著。     

并网异步风力发电机组模型及参数对其暂态稳定性的影响

建立了笼型异步发电机考虑定子电磁暂态的详细模型、忽略定子电磁暂态的简化模型、同时忽略定转子电磁暂态的稳态模型以及一个和两个质量块的风力机轴系模型.针对上述不同组合的5个风力发电机组模型,利用Matlab/Simulink对发电机端部发生三相短路故障情况下的机组暂态行为进行了仿真比较,并通过时域仿真求取了风力机组不同模型下机组故障临界切除时问.结果表明,采用不同风力机组模型对机组暂态稳定性分析结果有很大影响,发电机简化模型和两个质量块的风力机轴系模型较为合适.最后,以提出的合适模型为例,详细研究了风力机模型参数对机组暂态稳定性的影响.     

Low voltage ride through capability enhancement of wind turbine generator system during network disturbance

The energy capacitor system (ECS), composed of power electronic devices and electric double layer capacitor to enhance the low voltage ride through (LVRT) capability of fixed speed wind turbine generator system (WTGS) during network disturbance, is discussed. Control scheme of ECS is based on a sinusoidal pulse width modulation voltage source converter and DC?DC buck/boost converter composed of insulated gate bipolar transistors. Two-mass drive train model of WTGS is adopted because the drive train system modelling has great influence on the characteristics of wind generator system during network fault. Extensive analysis of symmetrical fault is performed with different voltage dip magnitudes and different time durations. Permanent fault because of unsuccessful reclosing is also analysed, which is one of the salient features of this study. A real grid code defined in the power system is considered and LVRT characteristic of WTGS is analysed. Finally, it is concluded that ECS (20 MW) can significantly enhance the LVRT capability of grid connected WTGS (50 MW) during network disturbance, where simulations have been carried out by using PSCAD/EMTDC.     

Wind turbine dynamic response?difference between connection to large utility network and isolated diesel micro-grid

The difference in dynamic behaviour of wind turbines connected to different size networks is analysed for synchronous and induction generators. Modal analysis has been applied to equivalent mechanical models of the wind turbine generator and the grid connection to show the difference in dynamics for a wind turbine generator connected to a large (interconnected) utility network or an (isolated) diesel micro-grid. Frequency domain analysis of these models has been used to quantify the effect of system parameters, such as enhanced drive train damping, diesel governor action and generator slip, on dynamic interaction. It has been shown that for wind turbines connected to a large grid an induction generator can reduce dynamic interaction. In contrast, for an isolated diesel micro-grid the diesel governor response and the compliance of the diesel generator dominate the system's dynamics, and the choice of either generator option for the wind turbine is dictated by other factors.     

Blade pitch control malfunction simulation in a wind energy conversion system with MPC five-level converter

This paper is on a wind energy conversion system simulation of a transient analysis due to a blade pitch control malfunction. The aim of the transient analysis is the study of the behavior of a back-to-back multiple point clamped five-level full-power converter implemented in a wind energy conversion system equipped with a permanent magnet synchronous generator. An alternate current link connects the system to the grid. The drive train is modeled by a three-mass model in order to simulate the dynamic effect of the wind on the tower. The control strategy is based on fractional-order control. Unbalance voltages in the DC-link capacitors are lessen due to the control strategy, balancing the capacitor banks voltages by a selection of the output voltage vectors. Simulation studies are carried out to evaluate not only the system behavior, but also the quality of the energy injected into the electric grid.     

Modelling and control of variable‐speed multi‐pole permanent magnet synchronous generator wind turbine

Emphasis of this article is on variable‐speed pitch‐controlled wind turbines with multi‐pole permanent magnet synchronous generator (PMSG) and on their extremely soft drive‐train shafts. A model and a control strategy for a full back‐to‐back converter wind turbine with multi‐pole PMSG are described. The model comprises submodels of the aerodynamic rotor, the drive‐train by a two‐mass model, the permanent magnet generator and the full‐scale converter system. The control strategy, which embraces both the wind turbine control itself and the control of the full‐scale converter, has tasks to control independently the active and reactive powers, to assist the power system and to ensure a stable normal operation of the wind turbine itself. A multi‐pole PMSG connected to the grid through a full‐scale converter has no inherent damping, and therefore, such configuration can become practically unstable, if no damping by means of external measures is applied. In this work, the frequency converter is designed to damp actively the drive‐train oscillations, thus ensuring stable operation. The dynamic performance of the presented model and control strategy is assessed and emphasized in normal operation conditions by means of simulations in the power system simulation tool DIgSILENT. Copyright © 2008 John Wiley & Sons, Ltd.     

Validation of fixed speed wind turbine dynamic models with measured data

Power system dynamics studies involving fixed-speed wind turbines normally use a wind turbine model consisting of two lumped masses, an elastic coupling and a induction generator model which neglects stator transients. However, validations of this model with measured data are rarely reported in the literature. This paper validates the model using a recorded case obtained in a fixed speed, stall regulated 180 kW wind turbine through a voltage dip. The work analyses the performance of the reduced order induction generator model which neglects stator transients, compared to the detailed induction generator model. It also includes a study of the convenience of representing mechanical damping in the drive train, and an evaluation of the single mass mechanical model.     

Modeling,control, and simulation of dual rotor wind turbine generator system

A new wind turbine generator system (WTGS) is introduced, and its mathematical model, blade pitch control scheme, and nonlinear simulation software for the performance prediction are presented. The notable feature of WTGS is that it consists of two rotor systems positioned horizontally at upwind and downwind locations, and a generator installed vertically inside the tower. In this paper, this new WTGS is treated as a constrained multi-body system, and the equations of motion are obtained by using the multi-body dynamics approach. Aerodynamic forces and torques generated from each of rotor blades are calculated using the blade element theory. Various pitch control schemes depending on the wind speed and the main rotor's rotational speed are implemented. A relatively simple model for the load torque is obtained by using the test data of the doubly fed induction generator adopted in the new WTGS. Finally, FORTRAN and Matlab/Simulink-based hybrid simulation software is developed and used to predict and analyze the performance of the WTGS.     

Transient and dynamic control of a variable speed wind turbine with synchronous generator

In this article, a controller for dynamic and transient control of a variable speed wind turbine with a full‐scale converter‐connected high‐speed synchronous generator is presented. First, the phenomenon of drive train oscillations in wind turbines with full‐scale converter‐connected generators is discussed. Based on this discussion, a controller is presented that dampens these oscillations without impacting on the power that the wind turbine injects into the grid. Since wind turbines are increasingly demanded to take over power system stabilizing and control tasks, the presented wind turbine design is further enhanced to support the grid in transient grid events. A controller is designed that allows the wind turbine to ride through transient grid faults. Since such faults often cause power system oscillations, another controller is added that enables the turbine to participate in the damping of such oscillations. It is concluded that the controllers presented keep the wind turbine stable under any operating conditions, and that they are capable of adding substantial damping to the power system. Copyright © 2007 John Wiley & Sons, Ltd.     

Wind turbine generator systems. The supply chain in China: Status and problems

Wind turbine generator systems (WTGS) manufacture is booming in China. The key to success of the wind turbine generator industry is to construct the supply chain. However few papers focus on the supply chain. In China, many enterprises have started to manufacture the wind turbine generator system and the components. The supply chain of the wind turbine generator system is not well established in China. Many key components of WTGS still need to be imported, such as the principal axis bearing and electrical control systems. We review the status of wind turbine generator system manufacturing and analyze the problems of the supply chain in China. We analyze the problems about the supply chain from a macroscopic view. The aims of this paper are to let more scholars and experts know the status of the WTGS supply chain and to do something for building a successful industry in China.     

Regulation of WTG dynamic response to parameter variations of analytic wind stochasticity

Although variable‐speed operation can reduce the impact of transient wind gusts and subsequent component fatigue, this is still an unknown factor that must now be quantified. Reduction in drive‐train stresses caused by fatigue loads in high wind turbulence is fundamental to realizing both output power leveling and long service life for a wind turbine generator (WTG). This paper presents an evolutionary controller comprising a linear quadratic Gaussian (LQG) and neurocontroller acting in tandem to effect optimal performance under high turbulence intensities, for a variable‐speed, fixed‐pitch WTG. The control objectives are maximum energy conversion and reduction in mechanical stresses on the system components. The proposed paradigm utilizes generator torque in controlling the rotor speed in relation to the highly turbulent wind speed, thereby ensuring the extracted aerodynamic power is maintained at a constant value, while shaft moments are regulated. The performance of the proposed controller is compared with that of the LQG and it is found that the former is more efficient in maintaining rated power, minimizing shaft torque variations, and shows robustness to parameter variations. Copyright © 2007 John Wiley & Sons, Ltd.     

大型失速型风力发电机动态特性研究

通过分析主动失速型机组的来流风速、气动、机械传动与发电机等部件的机理,建立了机组各主要部件的子系统模型(如气动模型、传动模型、发电机暂态模型、补偿电容模型、电网模型和控制系统模型等),近而得到了全系统的动态非线性模型。通过对机组全系统动态机理模型的数字仿真,得到机组在特定来流工况条件下的动态特性。所建立的模型和仿真结果为今后研究风电场与电网之间的相互影响提供了理论基础。     

风力发电机组塔架仿真和分析

简单介绍了风力发电机组塔架的类型和风力发电机组塔架设计的重要性。分别在某种参考风速及其风向改变90°和180°条件下,运用风力发电机组设计软件Bladed for Windows对风力发电机组塔架风载荷进行了仿真分析。最后,结合仿真结果和实际情况分析了叶片安装角、风轮锥角、风轮仰角、悬距、塔架气动阻力系数和塔架线密度等对塔架风载荷的影响。为风力发电机组的塔架设计提供了参考。     

低运行工况下直驱风电场电流内环主导的次同步振荡特性研究

针对低运行工况下直驱风电场接入弱电网出现的次同步振荡(sub-synchronous oscillation,SSO)问题,搭建直驱风电场、汽轮发电机组联网线性化模型,基于特征值分析法,识别系统中存在的振荡模式,分析电网强度、电流内环控制参数和并网数量对SSO模式的影响.基于净阻尼分析法,分析直驱风电场与汽轮发电机组的...     

1.5MW低风速风力发电机组主传动系统设计及动力学分析

低风速风力发电机组具有广阔的市场前景,其主传动系统的设计和分析是整个风机研发的关键技术之一。通过对风机各种传动系统结构形式的分析、对比和优化,设计了适于1.5 MW低风速风力发电机组的最佳传动方案,即内置式主轴、二级行星加一级平行轴齿轮传动的结构形式。采用多体动力学软件SIMPACK建立了该风机主传动系统的精确模型,找出系统的固有频率及激振源,并进行共振分析;对共振危险点进行时域仿真,根据仿真结果研究振动对风机系统的影响。最后根据系统的动态特性分析结果,验证所设计的主传动系统的可靠性。     

风气互补发电系统与电力系统相互影响的研究

为研究风气互补发电系统对电网的影响,首先搭建了由风电机组、燃气轮机、电网线路、静止无功补偿器、电力系统稳定器和大型水力发电机组成的仿真系统,并对该系统的负载侧和电网线路中部节点进行了稳定性分析。仿真结果表明,电网在加载了风气互补系统后运行能保持稳定,并能在发生短时故障后恢复到原来状态。该文为进一步研究风气互补系统与电网的相互影响提供了良好的模型基础。