近年来，随着风电等可再生能源发电的迅速发展，风电机组及其电力电子控制与交/直流电网间动态相互作用导致的新型次/超同步振荡问题引发了广泛关注。我国新疆哈密和冀北沽源等大规模风电并网系统均发生过严重的次/超同步振荡事件，危及电力设备的安全乃至系统整体的安全稳定运行。大规模风电并网系统设备类型众多、拓扑结构复杂、模型维数极高、运行方式多变，具有多时间尺度动态耦合特性，给系统的稳定分析带来极大的挑战。风电次/超同步振荡与常规同步发电机轴系扭振相关的次同步振荡在产生机理及稳定特性等方面均有显著区别，因此亟需针对此类新型振荡问题展开深入研究。为此，本文从高维系统建模、振荡稳定性分析与振荡安全域构建三方面入手，提出大规模风电次/超同步振荡问题研究的新理论和新方法。系统级建模方面，提出了刻画大规模风电并网系统次/超同步动态的阻抗网络模型，建立了网络的传递函数矩阵。模型构造灵活，可高效重构，且易于扩展，适合拓扑变化频繁、具有频率耦合效应的风电并网系统。阻抗网络模型能够反映复杂电网结构及其内部动态，为精确评估系统的次/超同步振荡特性分析奠定了模型基础。振荡稳定性分析方面，提出了频域模式分析方法，建立了参与因子、灵敏度等频域量化指标，可以获取系统的全部振荡模式，明确振荡的影响范围、振荡电流的空间分布规律和引发振荡的关键设备，从而全面反映风电次/超同步振荡特性。进一步，基于量化指标提出了阻抗网络的聚合判据和次同步相量测量装置的配置方法，为网络的空间聚合和测量装置的最优选址提供了理论依据。振荡安全域研究方面，提出了基于聚合阻抗模型和预测-校正技术的风电次/超同步振荡安全域构建方法，在确保安全域精度的条件下，显著提高了安全域构建效率。进一步，采用超平面对安全域边界点进行拟合，并基于边界表达式建立了系统运行状态的评价指标，可以获得系统在不同工况下的安全裕度，为系统运行方式的优化提供了重要指导。工程应用方面，基于所提出的建模和分析方法，开发了次/超同步振荡稳定性分析软件，并用于实际大规模风电并网系统，分析结果得到了电磁暂态仿真验证，为系统的安全稳定运行提供了有力支撑。
In recent years, renewable energy power generation, such as wind power has developed rapidly. The new sub/super-synchronous oscillation (SSO) issues caused by the interactions between wind turbine generators with power electronic control and AC/DC power grid have attracted wide attention. Serious SSO events have occurred in Hami, Northwest China and Guyuan of North China. They threatened the safety of equipment, and influenced the safety and stability of power systems.There are various types of components in large-scale wind power integrated power systems with variable operating conditions and multi-time scale dynamic couplings. Furthermore, the system topology is complex and the model dimension is high. These characteristics bring great challenges to the stability analysis of such systems. SSOs caused by wind power differ from those caused by conventional synchronous generators in mechanism and oscillation characteristics. Therefore, it is urgent to carry out in-depth research on this new type of oscillation. Thus, this paper proposes a new analysis method and theory, in terms of the modelling of high-dimension system, the analysis of oscillation characteristics and the construction of security region for SSOs. In the researches of system modeling, the impedance network model (INM) is proposed to describe the sub-/super-synchronous dynamics of large-scale wind power integrated power systems. The transfer function matrix of the network is established. The INM can be established and reconstructed efficiently. It can also be expanded easily. Thus it is suitable for wind power integrated power systems with variable operating conditions and multi-scale couplings. The INM reflects the complex topology of the system and its internal dynamics, which can be used for analyzing the oscillation characteristics of the system accurately. In the researches of oscillation characteristic analysis, the frequency-domain modal analysis method is proposed. The quantitative indexes such as participation factor and sensitivity are established. Based on the indexes, the affected area of the oscillation, the distribution of oscillation currents and the dominant components which cause the oscillation can be identified, thus fully reflecting the oscillation characteristics of SSOs. Furthermore, the aggregation criterion of INM and the configuration method of sub-synchronous phasor measurement devices are proposed based on the above quantitative indexes, which provide a theoretical basis for the spatial aggregation of INM and the optimal location of measurement devices.In the researches of security region (SR) analysis, the SR for SSOs caused by wind power is constructed based on the aggregated impedance and the predictor-corrector technique. The efficiency of SR construction is significantly improved via the proposed method with no loss of accuracy. Moreover, the boundary points of SR are fitted via the hyperplane, and the evaluation index of operating condition is built based on the analytical expression of boundary. Thus the safety margin of the system under different operating conditions are obtained, which provides useful guidance on the optimization of system operation mode.In the researches of engineering application, the software for SSO stability analysis is developed according to the proposed modeling and analysis method. The software has been used in the actual large-scale wind power integrated power system. The results have been verified by electromagnetic transient simulation, which are useful for the safe and stable operation of the system.
