LCL型并网逆变器谐振频率稳定域研究

Research on the Resonance Frequency Stable Region of LCL-type Grid-Connected Inverter

由于LCL网络可能带来的谐振现象,LCL滤波器的设计以及LCL型并网逆变器的稳定控制一直是2个极大的挑战。对此,利用系统开环频率特性和奈奎斯特稳定判据,分析了LCL型并网逆变器基于逆变器侧电流反馈的数字单环控制系统的稳定性,并得出了LCL滤波器的谐振频率在低于1/6采样频率时,系统无需附加额外阻尼即可稳定运行,且对网侧电感变化具有较好的鲁棒性,而在高于1/6采样频率时,系统在无附加阻尼条件下无法稳定的结论。这为LCL滤波器谐振频率范围的设计提供了指导,使得系统可以在无需附加阻尼的情况下获得较好的稳定性和鲁棒性。最后以LCL型三相三电平并网逆变器为例,进行了仿真分析和实验验证,结果证明了理论分析的正确性。

Due to the resonance phenomenon LCL network may bring,the design of LCL filter and the stable control of LCL-type grid-connected inverter have been both great challenges.For this,it analyzes the stability of inverter-side current feedback digital single-loop control system for LCL-type grid-connected inverter with the use of open-loop frequency characteristic and Nyquist stability criterion.It comes out that when the resonance frequency of the LCL filter is less than 1/6 of the sampling frequency,the system can operate stably with no need for adding extra damping and be of a good robustness with the variation of grid-side inductance,when the resonance frequency is higher than 1/6of the sampling frequency,the system cannot operate stably without adding damping.This provides the guidance for LCL filter resonance frequency range design,making the system have better stability and robustness with no need for adding extra damping.At last,in the case of LCL type three-phase three-level grid-connected inverter,simulation analysis and experiment verification is carried out,and the results prove the correctness of theoretical analysis.