风电机组低压穿越中的电力电子技术（上）

为了降低大规模风电并网对电力系统的影响．世界各国的电网运营商相继制定新的并网准则对并网风电场的输出特性作出严格规定,并网导则中的一项重要内容是要求风电场具有低压穿越（LVRT）能力。电力电子技术是提高风电场低电压穿越能力的重要手段,对于变速风电机组,电力电子设备已成为其标准配置,在低电压穿越过程中起到至关重要的作用;对...     

双馈电机风电场低电压穿越方案的研究

风电场并网准则对低电压穿越提出了明确的要求。对DFIG而言在电网电压严重跌落时,投入Crowbar可使DFIG短时不脱网运行。但是Crowbar的投入会使风电场吸收大量的无功功率,加重了电网的无功负担。采用STAT-COM可对风电场进行无功补偿,使其满足LVRT动态无功支撑的要求。因此,采用"单机机组安装转子Crowbar+风电场配备STATCOM"方案,可以很好满足双馈电机风电场的LVRT要求。     

风电机组的低压穿越改造

摘要：随着风电的快速发展及近年来频繁出现的风机脱网事故,要求并网风电机组具备低电压穿越功能：本文对不同机型的低压穿越技术方案进行分析,阐述风电场低压穿越改造的具体措施。     

双馈变流器不平衡控制的正负序分离方法比较研究

风电场并网导则要求风电机组在对称和不对称跌落下均具有低电压穿越能力,目前常用的几种不对称控制算法需要准确分离正负序分量。本文讨论了导数法、T/4延时法、移相90°全通滤波器法和陷波器法四种正负序分离方法的原理及优缺点,并对此四种方法在输入带高斯噪声、低次谐波、频率偏移时的分离效果进行了仿真比较研究。     

风力发电机、变流器及其低电压穿越概述

风力发电技术发展很快,单机容量不断增大,风电在电网中所占的比重也越来越大。讨论了几种典型的风力发电系统,包括失速型风电系统、双馈和直驱型变速恒频风电系统,并在此基础上,根据齿轮箱结构和发电机不同,讨论了其他类型的风电系统,分析了各自的优缺点。说明了常用的风电变流器拓扑,多电平变流器将得到更多的应用;为适应新的电阚规则对并网风电低电压穿趣与无功支持功能的要求,风电机组必须采取应对措施,对相关技术进行了分析和讨论。从风电系统发电机、变流器和低电压穿越能力等方面进行了论述,并介绍了不同风电公司的相关产品与技术。     

直驱变流器高压穿越控制策略研究

近年来风电机组的大规模并网带来的问题越来越受到关注,因电网电压骤升引起的事故逐年增加,因此风电机组的高电压穿越技术越来越受到重视。介绍一种直驱并网变流器的高电压穿越控制策略,通过提高变流器的无功调节能力和直流DBR电路配合控制的方法,当高电压发生时,变流器的电网检测模块检测到过压后,变流器进入HVRT模式,根据电压升高的水平向电网提供无功支持,直流母线泄放电路进行直流母线电压稳压控制,完成变流器暂态过程过渡,进入稳态。此方案可以在已有的低压穿越硬件基础上完成,经济易行,非常适合对已运行风电场的升级改造。     

基于非实时OS的毫秒级定时在LVRT测控系统中的实现

风电机组运行过程中,由于电网故障等原因,会出现瞬时电压跌落现象。本文研发了低电压穿越（LVRT）测控系统,监控测试风机的抗干扰性,提出一种在非实时系统中的高精度毫秒级定时方案,使用OS自带的定时函数嵌套调用实现精确定时的方法,解决了LVRT实时控制系统中高精度定时和资源占用率之间的矛盾,满足35kV/6MVA固定式电压跌落发生装置模拟电网的电压跌落与恢复精度,实现对电压跌落实时控制,同时实现了对电压跌落与恢复时风电机组运行状态的实时监测。该测控系统性能达到国际先进水平,已在风机电组低电压穿越测试中投入使用。     

基于风电场并网时风力发电机组的选取

随着环境污染的日益严重,雾霾等恶劣天气现象不断出现,清洁能源的开发利用显得尤为重要。而风能作为清洁能源具有成本低,可再生,永不枯竭的优点,风能的利用对于缓解环境污染等问题起到了积极的作用。如今我们国家风力发电技术正在迅猛的发展,也达到了较高的水平,伴随着技术的进步风电机组的装机容量一直在增加,风电在电网中所占的分量也不断增大。众所周知风能在利用时存在间歇性和随机性的问题,当许多大装机容量的风力发电机组并入电网时对电网的安全稳定运行也会带来重大的影响。比较突出的问题是风电场以及接近风电场的区域电力网会出现电力网的电压下降,更严重的是可能会导致电压崩溃造成严重的后果。因此风电场在并网时对于并网风电机组存在一定的要求,本文就并网发电机组的选取以及各机组特点进行分析介绍,使风电场在选取并网风电机具有参考价值。这样对于发展风能这个清洁能源,缓解环境污染带来的各种危害具有一定的作用。     

浅谈风电场并网运行安全管理措施

随着风力发电行业的快速发展,近年来并网投运发电的风电机组不断增加,如何确保并网发电的风电机组安全稳定运行成为政府监管机构、电网企业以及风电企业的关注重点,文章结合风电机组安全管理现状,介绍风电场并网运行的一些安全管理措施。     

双 ＰＷＭ 变换器式风电机组低电压穿越控制策略研究

风电机组运用了浆距角的控制原理,在低电压穿越状况下可以促使转动链受力而自动做出调整。为了促使风电机组低电压穿越的运行稳定,文章研究分析了风电机组低电压穿越时的特征和运行能力。电机侧变换器采用PI控制,电网侧变换器利用直流侧的控制得到给定值,最终促使电流实现闭环控制保持直流侧电压的平稳,仿真结果验证了本文内容的有效性与正确性。     

Steady as she blows [wind power, energy storage]

Power electronics and exotic energy storage devices are making wind power steady enough to compete with conventional electricity sources. Systems based on advanced power electronics and energy storage devices are massaging and managing power flows from wind turbines, enabling them to contribute to electricity grids without putting those grids at risk. Not only are the technologies making wind power more palatable to grid operators, they are even making it possible for engineers to finally harness wind energy's tremendous potential in wind-swept, remote locales. This article discusses the power electronic and energy storage technologies used in wind power.     

Current Source Inverter Based Grid Connected Hybrid PV-Wind Power Generation Unit

ABSTRACT

This paper presents a current source inverter (CSI)-based hybrid power generation system, which uses wind turbine and photovoltaic cells (PVs). A permanent magnet synchronous generator (PMSG) is connected to the CSI using a diode rectifier and a buck converter that is used to control the speed of the rotor. Another buck converter is used to control the maximum power point tracking of PVs. The operation of proposed system is studied under normal and grid voltage dip conditions. According to new grid codes, most power generating units are supposed to remain connected to the grid during voltage sag conditions and inject reactive current to grid as defined by grid codes. The CSI has fault current limiting capability that makes it appropriate to use in grid-connected applications and during voltage sag conditions in particular. The proposed system tracks the maximum power point of wind turbine and PVs under normal mode and injects required reactive current to the grid during voltage drop. However, incorporation of CSI with the inherent behaviour of wind turbine and PVs causes fault current to be within the tolerable range for power electronic devices. Simulations are carried out by using PSCAD/EMTDC software to verify the proposed system.     

Kraftwerkseigenschaften von Windenergieanlagen hinsichtlich Kurzschlussverhalten, Engpass- und Blindleistungsmanagement sowie Spannungsregelung

The increasing number of wind turbines will lead to new demands for transmission and distribution system control in the years to come. In order to ensure a smooth integration of wind energy into an electrical energy system structure, wind farms will have to possess power plant properties and be able to provide ancillary services. The ENERCON concept offers solutions not only for critical situations, such as short-circuits and bottlenecks in the grid, but also for normal operation, such as reactive power management or voltage control. Wind farms will essentially function in a manner similar to conventional power plants and moreover offer additional advantages in the distribution grid.     

Low Voltage Ride Through of Wind Farms With Cage Generators: STATCOM Versus SVC

This paper analyzes the extent to which the low voltage ride through (LVRT) capability of wind farms using squirrel cage generators can be enhanced by the use of a STATCOM, compared to the thyristor controlled static var compensator (SVC). The transient stability margin is proposed as the indicator of LVRT capability. A simplified analytical approach based on torque-slip characteristics is first proposed to quantify the effect of the STATCOM and the SVC on the transient stability margin. Results from experiments with a STATCOM and a 7.5 kW induction machine emulating a wind turbine are used to validate the suggested analytical approach. Further verifications based on detailed time-domain simulations are also provided. Calculations, simulations and measurements confirm how the increased STATCOM rating can provide an increased transient stability margin and thus enhanced LVRT capability. Compared to the SVC, the STATCOM gives a larger contribution to the transient margin as indicated by both calculations and simulations. The inaccuracies introduced by neglecting the flux transients in the suggested approach are discussed and found reasonable for an estimation method when considering the simplicity compared to detailed time-domain simulation studies. A method for estimating the required rating of different compensation devices to ensure stability after a fault is suggested based on the same approach.     

A Review of the State of the Art of Power Electronics for Wind Turbines

This paper reviews the power electronic applications for wind energy systems. Various wind turbine systems with different generators and power electronic converters are described, and different technical features are compared. The electrical topologies of wind farms with different wind turbines are summarized and the possible uses of power electronic converters with wind farms are shown. Finally, the possible methods of using the power electronic technology for improving wind turbine performance in power systems to meet the main grid connection requirements are discussed.      

电压骤降下双馈电机撬棒投切时刻对电网的无功功率影响

风力发电机规模和单机容量不断增大,电网对风力发电机之类的可再生能源并网有着极其严格的要求,其中最具挑战性的要求是低电压穿越,即在电网出现跌落时,要求风机在一定时间内不得脱网,直至发电机发出一定的无功功率帮助电网恢复。本文研究在电网出现大幅跌落时,通过控制撬棒投切的不同时刻,来讨论是否其投切时刻影响着系统从电网吸收的无功功功率,最终通过合理的投切时刻来最大程度上减少系统从电网吸收的无功功率,帮助电网更好的恢复。