计及频率耦合的单相并网逆变器阻抗建模及稳定性分析

Impedance modeling and stability analysis of single‑phase grid‑connected inverter considering frequency coupling

随着可再生能源渗透率的提高,电力电子变流器与大电网间的相互作用引发的振荡事故频发。为了研究新能源并网引发的振荡特征,本文通过实信号与复向量的联系解释了计及锁向环(phase⁃locked loop,PLL)影响时单相并网逆变器产生单频率扰动电压输入,双频率扰动电流输出的原因,并进一步解释了弱电网下产生频率耦合现象的机理,建立了自导纳和互导纳模型,进而推导出逆变器等效输出导纳,最后通过MATLAB/Simulink搭建模型进行仿真,验证了自导纳和互导纳模型的正确性,且最终给出的逆变器等效输出阻抗可根据奈奎斯特稳定判据准确判断系统稳定程度。

With the permeability increase of renewable energy,the interaction between power electronic converters and power grid causes oscillation accidents frequently.In order to study the characteristics of oscillation induced by gridconnected new energy sources,this paper explains the mechanism that a single-frequency disturbance voltage as input to a single-phase inverter considering the PLL effect leads to double-frequency disturbance current as output,through the relationship of real number signal and complex vector.The mechanism of frequency coupling in weak power grid is further explained.The models of self-admittance and mutual-admittance are established,and the equivalent output admittance of inverter is then derived.Finally,the correctness of the self-admittance and mutual-admittance models are verified by MATLAB/Simulink.The equivalent output impedance of inverter can be utilized to judge the stability of an interconnected system according to the Nyquist stability criterion.