基于谐波阻抗特性的风电次同步振荡分析

近年来,随着风力发电并网容量增加,电力电子技术被广泛使用,从而引发了新型次同步振荡问题。为应对该问题,提出了一种基于谐波阻抗特性的风电次同步振荡分析方法。通过IEEE第一标准模型对该方法的准确性和有效性进行了验证。文章建立了直驱风电场时域仿真系统,对机侧和网侧换流器进行详细建模仿真,并通过谐波阻抗特性对其进行分析,避免公式的推导和计算。结果表明,风机电力电子换流器在振荡频率下呈现较小的负值,即换流器表现为具有电容性的负阻抗,换流器呈现的电容性阻抗与交流电网的电感形成谐振回路,故系统存在次同步振荡的威胁。

Analysis of Sub-Synchronous Oscillation in Wind Farm According to Harmonic Impedance Characteristics

Recently， capacity of grid-connected wind power has increased， and power electronics technology has been widely used， causing new sub-synchronous oscillation problems. In order to cope with the problem， this paper proposes a method for analyzing the resonance characteristics of wind farms on the basis of impedance measurement. The effectiveness of the method is validated through the first IEEE benchmark model. A time-domain simulation model including direct-driven PMSGs and power electronic converters is established and it is analyzed on the basis of harmonic impedance measurement， which avoids complex formula derivations and calculations. The results show that the converter behaves as capacitive with negative impedance. The capacitive impedance of the converter forms a resonant loop with the inductance of the AC grid and causes unstable sub-synchronous oscillation.