近年来，对于新能源的开发利用，尤其是风能，已经受到世界各国越来越多的关注。迄今为止，大规模风电并网后对电力系统安全稳定运行的影响，特别是对电力系统小干扰稳定性的影响研究主要都是围绕双馈型风力发电机(Doubly-fed induction generator, DFIG)。和DFIG相比，直驱永磁型同步风力发电机(Permanent magnet synchronous generator, PMSG)具有发电效率高，无齿轮箱，维护成本低，可控性强等优点，将会成为风电发展的主流方向。本文针对大规模直驱永磁型风电场并网后对电力系统的小干扰稳定性问题进行了详细、深入的研究和探讨，主要成果归纳如下：经过大量的文献阅读，对不同类型风机的动态建模和并网后对电力系统的小干扰稳定性影响的研究概况进行了总结。在此基础之上，建立了直驱永磁型风电场的实用简化模型。在直驱永磁型同步风力发电机的建模中，引入了转子磁链定向控制策略；在发电机侧变频器的建模中，采用了定子电压定向控制策略，实现有功功率和无功功率的输出控制；在电网侧变频器的建模中，采用了电网电压定向控制策略，实现直流母线电压和并网无功功率的控制；在风电场的建模中，采用了风机等值的方法，建立了直驱永磁型风电场的等效模型。在特定风速条件下，以IEEE3机9节点系统和IEEE16机68节点系统为算例，考虑风电场取代系统中的同步发电机和风电场直接接入系统两种接入方式，分析研究大规模直驱永磁型风电场并网后对电力系统的小干扰稳定性的影响。在此基础之上，分析双馈型风电场和直驱永磁型风电场同时接入电网对电力系统的小干扰稳定性的影响，以及风电场之间的相互作用。考虑风速间歇、波动性，以IEEE16机68节点系统为算例，考虑风速的威布尔分布，运用蒙特卡罗模拟方法，从概率分析的角度出发探讨风电间歇、波动性对电力系统的机电振荡模式的影响；此外，假设风速线性变化，分析风电场出力渐变对电力系统的小干扰稳定性的影响。
In recent years, many countries around the world are increasingly concerned about the development and utilization of renewable energy resources, especially for the wind power. So far, much existing work corresponding to the impacts of grid-connected wind farm on the dynamic behavior of the power system mainly focused on the doubly-fed induction generator (DFIG) which is currently widely used in wind farms. Comparing with DFIG, the direct-driven permanent magnet synchronous generator (PMSG) is considered as an important alternative in the future development of wind power due to its higher generation efficiency, gearless structure, lower maintenance cost and higher operation reliability. This thesis will discuss the impacts of grid-connected wind farm of PMSG type on power system small signal stability elaborately and systematically. The main achievements are summarized as follows:After a comprehensive literature survey, the reviews on the dynamic modeling of different wind generators and small signal stability analysis of power system with high penetration of wind farm are summarized. Then, a practical simplified model of wind farm of PMSG type is derived. The rotor-flux-oriented control strategy is applied in the modeling of PMSG. As for the modeling of PMSG generator-side converter, based on the generator-voltage-oriented control strategy, the control of active power output and reactive power output can be realized. The grid-voltage-oriented control strategy is applied in the modeling of PMSG grid-side converter to realize the control of DC-link voltage and the reactive power regulation. The modeling of wind farm is to assume an equivalent wind generator.Under specific wind conditions, the small signal stability and the damping characteristics of power system with large-scale grid-connected wind farm of PMSG type are systematically studied in this thesis. Two simulation scenarios involving replacing synchronous generator with wind farm of PMSG type and direct connection to the power grid based on the IEEE 3-generator-9-bus test system and IEEE 16-generator-68-bus test system as benchmark are carried out to assess the effects of wind farm of PMSG type on power system small signal stability. Furthermore, the impacts of large-scale wind power on power system small signal stability with integration of wind farm of DFIG type and the wind farm of PMSG type simultaneously are studied, and the interaction effects between wind farms are analyzed elaborately.According to the characteristics of wind speed intermittency and fluctuation, the IEEE 16-generator-68-bus test system is conducted as benchmark to study the impacts of wind generation intermittency and fluctuation on small signal stability. Based on the Weibull distribution of wind speed, the Monte Carlo simulation technique based probabilistic small signal stability analysis is applied to explore and exploit the impact on the electromechanical oscillations. Furthermore, based on the linear variation of wind speed, the relationship between the change of wind power output and the small signal stability is studied deeply as well.
