电网强度视角下的新能源电力系统鲁棒稳定分析

Robust Stability Analysis for Renewable Energy Power Systems From the Perspective of Grid Strength

电网强度对以新能源主体的新型电力系统稳定性至关重要,然而,新能源电力电子设备的动态外特性难以详细建模,亟需从理论层面回答电网强度与系统鲁棒稳定之间的关系问题。该文研究异构新能源多馈入系统的电网强度作用机理并提出基于广义短路比的鲁棒稳定判据。首先,考虑设备导纳(阻抗)矩阵可能包含右半平面(right half plane,RHP)零点(极点),分析了单馈入系统短路比与系统互补灵敏度峰值之间的联系。其次,将异构多机系统小干扰模型分为同构多机系统(标称系统)及其乘性不确定性(摄动)的组合,对系统鲁棒稳定判据解耦和简化,所得结果表明最弱单馈入系统的互补灵敏度与最大单机摄动决定多机系统鲁棒稳定性。据此提出基于广义短路比的鲁棒稳定判据,即异构系统的鲁棒稳定性由标称同构系统的广义短路比与互补灵敏度峰值共同决定。最后,仿真算例说明所提方法的有效性。

Grid strength is very important to the stability of new power systems based on renewable energy sources.However,it is difficult to model the dynamic external characteristics of renewable energy power electronic equipment in detail.It is urgent to study the relationship between grid strength and system robustness from a theoretical level.This paper studied the mechanism of power grid strength of multi-infeed systems with heterogeneous power electronic and proposed a generalized short-circuit ratio based robust stability criterion.First,considering that the device admittance or impedance matrix may contain right half plane(RHP)zeros or poles,the relationship between the short-circuit ratio of the single infeed system and the peak of the system's complementary sensitivity was analyzed.Secondly,the heterogeneous multi-machine system small signal stability model was divided into a combination of a homogeneous multi-machine system(nominal system)and its multiplicative uncertainty(perturbation).By decoupling and simplifying the robust stability criterion of the system,the results show that the complementary sensitivity of the weakest single infeed system and the maximum single-machine perturbation determine the robust stability of the multi-machine system.Consequently,the generalized short-circuit ratio based robust stability criterion was proposed for the homogeneous system,where the heterogeneous system robust stability was determined by the generalized short-circuit ratio and the complementary sensitivity of the corresponding nominal system.Finally,a simulation example illustrated the effectiveness of the proposed method.