基于频域阻抗的新能源并网振荡风险评估方法

Risk Assessment Method for the Oscillation of Renewable Energy Grid-connected System Based on Frequency Domain Impedance

随着新能源装机规模不断增加,如何评估由其引发的系统次/超同步振荡风险是目前电网运行高度关注的重要问题。提出了一种基于频域阻抗的新能源并网振荡风险评估方法,首先利用系统各元件频域导纳模型形成网络节点导纳矩阵,实现对新能源场站并网点系统侧网络等效阻抗的计算,能准确反映电网结构特性以及网内其他设备的动态特性,然后结合新能源场站阻抗特性,通过阻抗分析评估新能源场站并网振荡风险。该方法采用电路节点分析法,算法易于实现,能够适应系统结构和运行方式变化,充分反映网侧动态元件的影响,可利用电网同步相量测量装置提供的结构和潮流数据对系统内新能源场站并网振荡风险进行评估分析。以某地区实际电力系统为研究对象,利用所提方法展开了次同步振荡风险评估,同时基于特征值法和时域仿真验证了评估结果的准确性和评估方法的有效性。

With the increasing installed capacity of renewable energy,how to assess the risk of sub/sup-synchronous os-cillation in power system caused by it is currently a critical concern for grid operation.This paper proposes a risk assessment method for the oscillation of renewable energy grid-connected system based on frequency domain impedance.Firstly,the frequency domain admittance model of each component in the system is used to form a network node admit-tance matrix so as to calculate the equivalent impedance of the network at the system side of the grid connection point of the renewable energy station,which can accurately reflect the structural characteristics of the power grid and the dynamic characteristics of other equipment in the grid.Combined with the impedance characteristics of the renewable energy sta-tion,the oscillation risk of the grid-connected renewable energy station is evaluated by impedance analysis.The nodal analysis is utilized in the method,which is easy to implement algorithmically and can adapt to the changes of system structure and operation mode,thus the influence of dynamic components on the grid side can also be fully reflected.The data of topological structure and power flow provided by the phasor measurement unit(PMU)can be used to evaluate the oscillation risk of grid-connected renewable energy stations in the system.Taking an actual power system in a certain area as the research object,we perform the risk assessment of subsynchronous oscillation by using the proposed method.The correctness of the assessment results and the effectiveness of the assessment method are verified based on the eigenvalue method and time domain simulation.