风电机群电网故障下不脱网可控对策及对电网暂态同步稳定影响研究

This proposal aims to investigate the basic theories and key technologies of ride-through operation of large-scale typical wind turbines with high penetrations, as well as transient synchronizing control of power network under transient grid fault conditions, i.e., symmetrical/asymmetrical and high/low voltage faults. The typical wind turbines are based on doubly fed induction generators and fully rated converters, respectively. The impacts of transient grid faults on the typical wind turbines and their various fault behaviors on the power network with large-scale wind powers are identified and analyzed in detail. The ride-through control strategies of wind turbines are presented to enhance the transient synchronizing stability of power system with highly-penetrated wind power. The specific research contents contain transient modeling of faulted network, typical wind turbines and their grid- / machine-side converters in terms of positive- / negative-sequence components in natural and forced electromagnetic quantities; mutual influence and interdependence between transient fault network and typical wind turbines; transient control strategies of typical wind turbines to realize their ride-through operations during network faults; transient synchronizing control theory of wind turbines as well as the optimization methodology of their active/reactive outputs and ramp characteristics under faulted network conditions. The achievements of this proposal will change the backward situation in China in terms of investigating controllable ride-through operation of large-scale highly-penetrated wind turbines, especially the transient synchronizing control of power network under the conditions of transient grid faults. These research results will be in advanced level compared with foreign wind power generation technology in theory, and will provide theoretical support and reference to solve the issues on large amounts of wind turbines’ grid disconnections in China at present. Further, the accomplishment of this proposal is to contribute to the reinforcement of security and stability of power network with highly-penetrated wind turbines and will promote larger scale of development and utilization of wind power in China in the future.

本项目研究电网暂态故障（对称、不对称暂态高、低电压）下大规模集中并网典型风电机群（双馈型、全功率型）的不脱网可控运行及电网暂态同步稳定控制的基础理论和关键技术，包括暂态故障对风电机组及风电机群故障行为对含大规模风电电力系统的影响评估；电网故障下增强含大规模风电电力系统暂态同步稳定的风电机群不脱网可控对策研究。具体研究：包括故障电网、典型风机、变流器在内的完整风电机组暂态模型；故障电网与风电机群间的相互影响与依存关系；电网故障下典型风电机群不脱网运行的暂态控制策略；电网故障下风电机群的暂态同步控制理论及有功、无功出力与爬坡特性优化方法。本项目的研究将改变我国尚未对大规模集中并网风电在电网暂态故障下的不脱网可控运行及电网暂态同步稳定控制研究的落后局面，使理论成果领先国际风电技术研究水平，为解决我国风电大面积脱网提供支撑，增强含大规模风电电力系统的安全稳定运行能力，推动我国风电规模化开发与利用。

大规模集中开发、远距离输送是目前我国开发利用风电的主要方式。随着风电渗透率的不断提升，主要风电基地并网点电网强度变弱，风机群与电网之间的耦合特征日渐凸显。现有风机暂态故障穿越控制基于强电网背景的单机穿越理论而设计，因而在新的电网环境下面临严峻挑战。本项目着眼于风机群协同穿越这一目标，根据故障穿越过程中各阶段的主要扰动形式，研究探索弱电网下风机与电网之间、多风机之间动态耦合所引起的应力和稳定问题。本项目：.1.分析了故障发生后双馈风机在电流控制时间尺度内的电流暂态应力问题。建立了含故障网络计及机网耦合的双馈风机暂态应力分析模型；分析了网络阻抗和控制参数对单机暂态穿越行为的影响；进而分析了风机间相互作用下的电流暂态分布应力。.2.分析了故障恢复阶段机网耦合带来的风机端暂态过电压问题。建立了计及机网耦合反映故障恢复风机端电压幅值动态的数学模型，提出了风机端电压控制动态惯量的表达式，分析了控制器参数、电网强度等因素与动态惯量大小之间的关系。基于得到的端电压控制惯量，分析了机网耦合下故障恢复过电压产生的机理以及端电压控制惯量大小与过电压幅值间的联系机理。.3.分析了故障持续期间机网三型和四型风电机组低频振荡失稳的问题。建立了电网故障期间包括高阻抗交流电网在内的并网风机完整小扰动模型，分析了机网相互作用贡献的负阻尼特征，剖析了控制参数、电流指令以及机电运行点对系统阻尼的影响机理。.结合项目研究，培养已毕业硕士2名，在读博士生4名。已发表IEEE Transaction论文7篇（SCI收录，含2篇已录用），EI论文7篇，获国家发明专利授权4项，获省部级奖励2项。作为弱电网条件下暂态故障穿越方面的探索性研究，本研究工作有助于理解风机与电网之间、风机与风机间的耦合机理及其对故障穿越期间电磁应力和稳定性的影响，是大型风电场精细建模、特别是考虑电力系统暂态稳定性的建模分析工作的基础，同时也对优化风机群在弱电网下的暂态故障穿越控制策略具有工程指导意义。