光伏并网系统的谐波谐振评估与安全防控

Study on Harmonic Resonance of Photovoltaic Grid-Connected System

随着大量新能源发电接入电力系统,光伏并网系统中光伏逆变器输出阻抗与电网侧等效阻抗在并网交点处的等效阻抗和出现极小值,此时电网电流迅速增大引发系统的谐振问题,因此有必要构建光伏逆变器参数的稳定域从而对系统是否发生谐波谐振进行评估和预警。对此,为了研究光伏逆变器与电网中谐波谐振交互影响的问题,提出了一种新型模态分析法,建立了光伏谐波源的诺顿等效模型并推导出逆变器的等效输出阻抗公式,基于Gerschgorin圆盘定理求解状态矩阵的最优相似变换模型,以此构建出光伏逆变器参数的安全域并与传统的逐点法进行对比,算例仿真结果表明了该方法在计算准确性和计算效率方面的优越性。

Under the background of new energy power system,the fundamental reason for the harmonic resonance of photovoltaic grid-connected system is that the equivalent impedance sum between the output impedance of photovoltaic inverter and the grid side appears minimum at the grid-connected intersection point.At this time,the rapid increase of grid current causes the system resonance problem.Therefore,it is necessary to construct the stability domain of photovoltaic inverter parameters so as to evaluate and early warning whether the system has harmonic resonance.In this paper,a new modal analysis method is proposed to analyze the interaction between the photovoltaic inverter and the harmonic resonance in the power grid.Then,the Norton equivalent model of the photovoltaic harmonic source is established and the equivalent output impedance formula of the inverter is derived.The optimal similarity transformation of the state matrix is carried out based on Gerschgorin′s disk theorem.Compared with the traditional point-by-point method,the safety domain of photovoltaic inverter parameters is constructed,and the advantages of the proposed method in computational accuracy and efficiency are proved.