【作者】 王磊；

【导师】 贾宏杰；

【作者基本信息】 天津大学 ， 电力系统及其自动化， 2012， 博士

【摘要】 针对近来风电机组连锁脱网事故频发的问题，本文从双馈风电机组（Doubly-fed Induction Generator，DFIG）的本身特性出发，研究连锁脱网事故的诱因和改善措施。为分析基于双馈风电机组风电场的特性，首先在DIgSILENT/PowerFactory（Digital SImuLation and Electrical NeTwork）平台中建立了DFIG详细仿真模型；然后提出了一种附加阻尼控制策略，以抑制风电场并网而导致的大电网阻尼降低问题；进一步，研究通过增加无功补偿装置以及对DFIG实施无功协调控制策略来提高电力系统小扰动稳定性的方法。本文主要工作如下：（1）建立了双馈风电机组的小扰动动态分析模型，深入探讨了风电场与大电网联络紧密程度、风电场出力、风电场连接方式对系统小扰动稳定性的影响，以揭示双馈风电机组连锁脱网事故的机理。通过单机-无穷大系统和新英格兰39节点系统接入风电场的仿真算例，示例并分析风电场脱网的可能诱因。（2）在深入理论研究基础上，提出了一种植于双馈风电机组变频器上的附加阻尼控制策略。该附加控制部分类似于传统发电机的PSS（Power SystemStabilizer）附加阻尼器，它可在不增加附属控制装置情况下，通过变频器附加控制来增加系统阻尼。利用风电场并网到四机两区域系统和十机四区域系统的算例分析，表明该附加阻尼控制策略能够有效提高电力系统的阻尼，从而改善系统的小扰动稳定性。（3）通过对风电场脱网事故的现场分析发现，在故障发展过程中，未脱网风机会从系统吸收大量无功。为防止在故障中，因无功需求激增而导致风电场电压的进一步波动，本文提出通过增加并联静止同步补偿器来稳定系统电压的补偿方案。依据风电场无功功率输出特性，在风电场出口安装无功补偿装置，并对补偿装置的容量进行优化配置，达到优化无功输出及稳定系统运行的目的。利用四机两区域系统算例，通过特征值分析发现，通过增加无功补偿装置能够有效改善系统的稳定性，有利于抑制脱网事故。（4）为了取代昂贵的无功补偿装置，提出了通过改善双馈风电机组自身控制策略来提高风电场出口电压，并减少吸收无功功率的实现思路，即通过变频器自身控制来改善风力发电机动态特性以提高系统稳定性。利用单台双馈风电机组和大规模风电场等不同场景，通过仿真验证了所提方法的有效性。更多还原

【Abstract】 For the recent wind turbine cascading trip-off, the paper starts from theunderlying mechanism of DFIG (Doubly-fed Induction Generator) to study thetrip-off causes and seek improvement measures. In order to analyze the characteristicsof wind farm, firstly, the detailed simulation models of DFIG are established inDIgSILENT/PowerFactory (Digital SImuLation and Electrical NeTwork). Secondly,additional control strategy is proposed for DFIG converter, to inhibit weak dampingof power system integrated with wind farm. Finally, Var compensation device and Varcoordinated control strategy is proposed, to improve Small Signal Stability of powersystem. The main work of this paper is as follows:(1) A Small Signal dynamic model of DFIG is established. And then furtherdiscussion on the tightness of integration, the output of wind farm, and the connectionschemes of wind farm impact on the Small Signal Stability of power system arecarried out to reveal the nature of cascading trip-off from grid. Through singlemachine infinite system and New England39system, the incentives of wind farmtrip-off from grid are analyzed.(2) A Supplementary Damping Control System (SDCS) is proposed, and is addedinto the DFIG converter. The SDCS is similar to the PSS (Power System Stabilizer)of conventional generator, which can improve the system damping by convertercontroller, without any other additional device. Simulations based on Four-machineTwo-area and Ten-machine Four-area systems are carried out, and the results revealthat the proposed control strategy can improve the power system damping and thenimprove the Small Signal Stability of power system.(3) The actual analysis of trip-off phenomenon shows that wind turbine requires alarge amount of reactive power during the development of trip-off. In order to preventfurther fluctuations of voltage during trip-off, due to the surge of reactive powerdemand, STATCOM (Static Synchronous Compensator) is proposed to stabilize thesystem voltage. According to the reactive power characteristics of wind farm, Varcompensation device is installed at PCC (Point of Common Coupling). By analyzingthe eigenvalues of Four-machine Two-area integrated with wind farm, the STATCOMcan improve the stability of power system and inhibit cascading trip-off. (4) Var coordinated control strategy is proposed, instead of expensive reactivecompensation devices, to improve the voltage of PCC and reduce the absorption ofreactive power. The proposed converter controller can improve the dynamiccharacteristics of wind turbine, to improve the stability of power system. Single DFIGand large scale wind farm are analyzed, to verify the proposed Var coordinatedcontrol strategy.更多还原