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 grid-connected 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.
关键词
频率耦合/单相并网逆变器/锁相环/输出阻抗/稳定性
Key words
frequency coupling/single-phase grid-connected inverter/phase-locked loop/output impedance/stability analysis
维普
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