并网逆变器整体序阻抗建模方法及其稳定性分析

Overall Sequence Impedance Model of Grid-connected Inverter and Its Stability Analysis

在高比例新能源电力系统中,并网逆变器与电网的动态交互作用使得系统谐波谐振问题凸显且日趋复杂。以三相平衡系统为研究对象,研究abc坐标系下考虑正负序频率耦合以及逆变器与电网阻抗交互影响的并网系统整体序阻抗建模方法,以避免行列式计算,并率先提出并网系统整体阻抗测量方法;进而在整体阻抗模型基础上,提出一种频域阻抗稳定性判据和振荡频率预测方法,可建立频域阻抗判据与并网系统物理环节的联系,以大幅降低频域阻抗判据误判的风险;最后,通过MATLAB/Simulink仿真扫频验证了系统整体阻抗模型的正确性,并通过RTLAB硬件在环实验证明其可用于新能源并网系统的稳定性判断,并具有谐振频率预测精度高的优点。

In a high-proportion new energy power system,the dynamic interaction between the inverter and the grid makes the system harmonic resonance problem prominent and increasingly complex.This paper takes the three-phase balanced system as the research object,studies the overall sequence impedance modeling method of the grid-connected system considering the positive and negative sequence frequency coupling and the interaction between the inverter and the grid impedance under the abc coordinate system,so as to avoid the determinant calculation.This paper pioneers the overall impedance measurement method of the grid-connected system.Furthermore,on the basis of the overall impedance model,a frequency-domain impedance stability criterion and an oscillation frequency prediction method are proposed,which can establish the connection between the frequency-domain impedance criterion and the physical links of the grid-connected system,in order to greatly reduce the risks of misjudgment.Finally,the correctness of the overall impedance model of the system is verified by frequency sweeping through MATLAB/Simulink simulation.RTLAB hardware-in-the-loop experiments proves that it can be used to judge the stability of grid-connected systems,and has the advantage of high accuracy of resonant frequency prediction.