含双馈风电场的电力系统低频振荡模态分析

Modal Analysis of the Low-frequency Oscillation of Power Systems With DFIG-based Wind Farms

大规模风电场接入电网可能增加区域间和局部区域低频振荡和风电机组轴系扭振的风险。研究了含双馈风电场的电力系统低频振荡特性;在考虑风力机传动链、变桨控制和双馈发电机动态模型及其控制策略的情况下,建立含双馈风电场的电力系统小信号稳定性分析的详细模型;采用模态分析方法,分析了IEEE两区域四机的双馈风电系统低频振荡模态,并通过时域仿真验证了模型和模态分析的正确性。针对风电接入潮流不变和改变两种情况,研究了风电场不同运行工况、接入容量以及是否参与无功调度对系统区域间、局部振荡模态以及风电机组轴系振荡模态的影响。结果表明,含双馈风电场的系统低频振荡特性不仅受风电场运行控制及其容量大小的影响,而且与接入系统潮流变化情况密切相关,采用同步电机协调控制方式使得系统潮流不变时将有助于改善系统区域间振荡模态的阻尼。

The grid integration of large scale wind power may increase the risks of inter-area low frequency, local power oscillations and the shaft torsion oscillation of the wind turbine. The paper studied the influence of the integration of doubly fed induction generator （DFIG）-based wind farms integration on the low frequency oscillation characteristics of the power system. In order to do small signal stability analysis, a detailed mathematical model was established by considering the effects of wind turbine drive drain, variable pitch control, dynamic models and control strategy of DFIG. By using modal analysis method low-frequency oscillation modes in an IEEE two-area four-machine power system with DFIG-based wind farm were investigated, and the results of the time-domain simulation demonstrated the validity and effectiveness of the model and the corresponding analysis. In the two cases of the constant and variable power flow, the characteristics of local oscillation modes, inter-area oscillation modes, and shaft torsional vibration modes were respectively analyzed under variable operational conditions, including different operation points, different integrated capacity of wind power and whether wind farm participates in reactive power dispatching. The results show that low-frequency oscillation characteristics are closely related to the variation of the power flow, the control strategy and the capacity of wind farm. A suitable coordinated control scheme of synchronous generators could improve the oscillation damping in the condition of constant power flow.