电网故障下全功率风电场内部机组的暂态稳定性分析

Transient stability analysis of wind turbines with a full-scale converter under grid fault

全功率风电场中机组并网运行的稳定性往往与网侧变流器的控制和并网阻抗有关,因而风电场中机组的失稳并不是同时发生的。为揭示风电场中机组的位置与其暂态稳定性的关系以及机组间稳定性的相互影响,建立了基于锁相环的多风电机组非线性降阶模型。基于等面积法的思想,分析了不同运行条件下风电场内部不同机组的暂态稳定裕度以及场内线路阻抗对稳定性的影响。通过Matlab/Simulink时域仿真,进行了定量分析和验证。结果表明,风电场内馈线阻抗将减少输出电流流经该阻抗所联接机组的暂态稳定域,而对输出电流不流经该阻抗的其他机组的暂态稳定性影响很小。阻抗上流过的电流越大,其对稳定裕度的缩减也越明显,因而,随着链接机组台数增多,不能简单忽略场内阻抗对稳定性的影响。此外,在相同条件下,有功出力大的机组将更易失稳。

The stability of grid-connected operation of full-scale wind turbines in wind farms is often related to the control of the grid-side converter of the turbine and the impedance between grid and the turbine. Therefore, the instability of wind turbines in a wind farm does not always occur at the same time. In order to reveal the relationship between the location of wind turbines and their transient stability, as well as the interaction on stability between wind turbines, a nonlinear reduced order model of multi wind turbines based on phase-locked loop is established. Based on the theory of equal-area-principle, the transient stability margin of different turbines in the wind farm under different operating conditions and the influence of line impedance on the stability are then analyzed. Through Matlab/Simulink time domain simulation, quantitative analysis and verification are carried out. The results show that the feeder impedance in the wind farm will reduce the transient stability region of the connected turbines whose output current flow through the impedance,and has little effect on the transient stability of other turbines whose output current does not flow through the impedance.The greater the current flowing through the impedance is, the smaller the stability margin. Therefore, with the increase of the number of turbines linked on a feeder line, the impact of the internal impedance of a wind farm on stability cannot be simply ignored. In addition, the larger output of a wind turbine, the easier it is for it to become unstable under the same conditions.