弱电网中LLCL型并网逆变器的谐振分析与抑制策略研究

RESEARCH ON RESONANCE ANALYSIS AND SUPPRESSION STRATEGY OF GRID-CONNECTED INVERTER WITH LLCL FILTER IN WEAK GRID

针对弱电网中多个LLCL型并网逆变器并联运行的谐振问题,提出一种混合阻尼控制策略。在建立多LLCL型并网逆变器的数学模型基础上,分析多机并联谐振的产生机理,得出电网阻抗和LLCL滤波器参数变化是产生谐振的关键因素,将影响系统并网运行的稳定性。为此,在不改变LLCL型并网逆变器拓扑结构的前提下,将所提控制策略应用到弱电网多机并联系统中。仿真与实验结果表明,该控制策略能有效地抑制系统谐振,降低并网电流和电压的谐波含量,提高在弱电网条件下多机并联运行的稳定性。

To solve the resonance problem of multiple parallel grid-connected inverters with LLCL filter in weak grid,a hybrid damping control strategy is proposed in this paper. Based on the mathematical model of multiple grid-connected inverters with LLCL filter,the mechanism of multi-inverter parallel resonance is analyzed. And the conclusion can be conducted that the key factors of resonance are the change of grid impedance and LLCL filter parameters,which will affect the stability of the system grid-connected operation.Therefore,on the premise of not changing the topology of LLCL-filter-based grid-connected inverter,the proposed control strategy is applied to the multi-inverter paralleled weak grid system. Simulation and experimental results show that the proposed control strategy can effectively suppress the system resonance,reduce the harmonic content of the grid-connected current and voltage,and improve the stability of multi-inverter parallel operation under weak grid conditions.