直驱风电场和串补之间的次同步振荡风险

随着电网规模的持续扩大，串补长距离输电系统引发的次同步振荡现象频现。因此，如何探析串补输电系统失稳的深层原因是当前系统稳定性分析发展方向之一。本文基于开环模式谐振理论，提出了一种串补输电线路引发次同步振荡的开环模式谐振分析方法，文章首先建立了直驱风电场外接串补输电线路的小信号模型，并通过开环模式谐振分析方法研究了串补线路和直驱风电场之间的动态交互作用。结果表明串补主导的开环次同步振荡模式与风电场主导的开环次同步振荡模式在复平面靠近时，系统的闭环稳定性将会下降，并运用残差指标成功预测了开环模式谐振条件下闭环模式的位置，而改变风机参数或调整串补度可以规避动态交互的发生。本文通过算例系统验证了上述理论分析的正确性，证明直驱风电场通过串补输电线路进行输电时存在一定的失稳风险，能在一定程度上为串补输电系统的参数整定提供借鉴。

Sub-synchronous oscillation risk between PMSG farm and series complement

With the continuous expansion of power grid scale, the phenomenon of subsynchronous oscillation caused by series compensated long-distance transmission system occurs frequently. Therefore, how to analyze the deep causes of series compensated transmission system instability is one of the development directions of system stability analysis. Based on the open-loop mode resonance theory, an open-loop mode resonance analysis method of subsynchronous oscillation caused by series compensated transmission line is proposed in this paper. Firstly, the small signal model of external series compensated transmission line of PMSG farm is established, and the dynamic interaction between series compensated line and direct drive wind farm is studied by open-loop mode resonance analysis method. The results show that when the open-loop subsynchronous oscillation mode dominated by series compensation and the open-loop subsynchronous oscillation mode dominated by wind farm are close in complex plane, the closed-loop stability of the system will decline, and the position of the closed-loop mode under the resonance condition of the open-loop mode is successfully predicted by using the residual index. Changing the PMSG parameters or adjusting the series compensation can avoid the occurrence of dynamic interaction. This paper systematically verifies the correctness of the above theoretical analysis through an example, and proves that there is a certain risk of instability when the PMSG farm transmits power through the series compensated transmission line, which can provide reference for the parameter setting of the series compensated transmission system to a certain extent.