考虑电网阻抗变化的LLCL并网逆变器谐振抑制策略

弱电网条件下,并网逆变器的正常工作会受到电网背景谐波及电网阻抗动态变化的影响,并网电流出现谐波谐振现象.为此,提出一种LLCL并网逆变器谐振抑制新策略.该策略在加权电流控制和电网电压前馈控制的基础上,引入电容电流反馈环节,保留了传统电网电压前馈控制方法中消除电网电压产生畸变影响并网电流的优点.通过对新反馈环节中反馈系数的设置,实现谐振尖峰的有效抑制,同时使并网逆变器的稳定性不受电网阻抗的影响,提高了LLCL并网逆变器的稳定性,降低了并网电流的谐波含量.最后,搭建仿真和实验平台,验证了谐振抑制新策略的有效性.

Resonance suppression strategy of LLCL grid-connected inverter considering change of power network impedance

Under the condition of weak grid, the normal operation of the grid-connected inverter will be affected by the background harmonics of the grid and the dynamic changes of the grid impedance, resulting harmonic resonance occurring in the grid-connected current. Therefore, a new resonant suppression strategy for LLCL grid-connected inverters is proposed. Based on the weighted average current control and grid voltage feedforward control, the strategy introduces the capacitive current feedback link, which preserves the advantages of eliminating the influence of grid voltage on the grid-connected current in the traditional grid voltage feedforward control method.By setting the feedback coefficient in the new feedback link, the resonance peak can be effectively suppressed, and at the same time, the stability of the grid-connected inverter is not affected by the grid impedance, which improves the stability of the LLCL grid-connected inverter and reduces the harmonic content of the grid-connected current. Finally, the effectiveness of the new strategy of resonance suppression is verified by building the simulation and experimental platform.