基于改进复转矩系数法的风电场并网引发电力系统次同步振荡研究

Study on Sub-Synchronous Oscillations of Power Systems Caused by Grid-Connected Wind Farms Based on the Improved Complex Torque Coefficients Method

针对并网风电场与同步机组之间的动态交互作用引发的电力系统轴系次同步振荡问题,建立了多输入多输出闭环互联系统模型,将系统划分为同步机子系统和风电场子系统。在指出传统复转矩系数法局限性的基础上,提出一种基于特征值灵敏度的改进复转矩系数法,兼顾考虑了风电场并网引入的稳态潮流变化影响和动态交互作用影响。最后,通过对示例系统的仿真分析验证了所提出方法在含并网风电场的单机和多机电力系统次同步振荡稳定性研究中的有效性,从阻尼机理角度对同步机轴系与双馈风电场之间的近似强模式谐振现象做出了解释,并分析了风机换流器控制环节参数、输电系统负荷大小及风火发电机之间动态交互作用对同步机轴系与风机控制系统之间近似强模式谐振的影响。

To examine the torsional sub-synchronous oscillations of power system systems caused by the dynamic interactions between grid-connected wind farms and synchronous units, this paper establishes a multi-input and multi-output closed-loop interconnect system model, which divides the system into synchronous machine subsystem and wind farm subsystem. On the basis of pointing out the defects of the traditional complex torque coefficients method, an improved complex torque coefficients method based on eigenvalue sensitivity is proposed. The effects of the variation of steady-state flow and dynamic interactions introduced by integration of wind farms are considered. Finally, the effectiveness of the proposed method in a single-machine and a multi-machine power system with grid-connected wind farms is verified by simulation analysis. From the perspective of damping mechanism, the near strong modal resonance phenomenon between the synchronous machine shaft system and the DFIG wind farm is explained. The influence of the control parameters of the VSC, the load of the transmission system and the level of the dynamic interactions on the near strong modal resonance between the shaft system of synchronous generators and control system of the wind farms are analyzed.