考虑交直流谐波耦合的并网逆变器建模与分析

Modeling and analysis of grid-connected inverter considering AC and DC harmonic coupling

可再生能源的大规模开发利用使得逆变器在电网中的比例越来越高,逆变器与电网间谐波交互作用也愈加频繁和复杂。针对传统的建模方法无法体现逆变器与电网间谐波交互耦合的问题,文中基于谐波状态空间(HSS)理论对三相并网逆变器进行建模,该模型将交直流侧的多个频次谐波考虑在内,具有较高的精度。基于HSS模型推导出输入到输出的谐波传递函数矩阵,建立逆变器交直流谐波耦合导纳幅值图,探究交直流谐波耦合关系。然后,提出了一种适用于闭环控制系统的三相并网逆变器小信号HSS建模方法,通过计算特征值对系统稳定性进行评估以及对振荡频率进行预测。最后与MATLAB/Simulink仿真结果进行对比,验证了所建立HSS模型的准确性和系统稳定性分析的正确性。

The large-scale development and utilization of renewable energy has made the proportion of inverters in the power grid higher and higher,and the harmonic interaction between the inverter and the power grid has become more frequent and complex.Aiming at the problem that the traditional modeling method cannot reflect the inter-harmonic interaction coupling between the inverter and the power grid,the three-phase grid-connected inverter is modeled based on the harmonic state space(HSS)theory.This model takes into account the multiple frequency harmonics on the AC and DC sides,and has high accuracy.Based on the HSS model,the input-to-output harmonic transfer function matrix is derived,the AC/DC harmonic coupling admittance amplitude diagram of the inverter is established,and the AC/DC harmonic coupling relationship is explored.Then,a small-signal HSS modeling method for three-phase grid-connected inverters suitable for closed-loop control systems is proposed,which evaluates the stability of the system and predicts the oscillation frequency by calculating eigenvalues.Finally,the accuracy of the established HSS model and the correctness of the system stability analysis are verified by comparing with the simulation results of MATLAB/Simulink.