抑制谐波谐振的并网逆变器机侧电流反馈的CVFAD设计方法

Design method for CVFAD of grid-connected inverter inverter-side current feedback with harmonic resonance suppression

LCL型并网逆变器机侧电流反馈控制较并网电流反馈控制具有更高的稳定性。但受数字控制延时的影响,系统的稳定性取决于谐振频率与采样频率的比值。且谐振频率附近存在一个谐波放大频域,在弱电网工况下易引发谐波谐振现象。而传统机侧电流反馈的双环控制方法受带宽限制,无法达到理想的稳定分界频率。针对该问题,提出一种电容电压有源阻尼的新型控制方法。该方法采用电容电压反馈内环提升系统阻尼效果,通过附加电容电压反馈回路使得系统开环零点重新配置,达到消除反向谐振峰的目的。理论分析表明,所提方法拓宽了系统稳定区间,不仅消除了谐波放大频域,且在电网阻抗宽范围变化时,系统始终具有较高的鲁棒性和控制性能。最后,通过仿真和实验验证了理论分析的正确性和所提方法的有效性。

LCL-type grid-connected inverter inverter-side current feedback control has higher stability than grid-connected current feedback control.However,its stability is dependent on the ratio of the resonant frequency to the sampling frequency because of the influence of digital control delay.Additionally,there exists a harmonic amplification frequency domain near the resonant frequency.This can lead to harmonic resonance phenomena,particularly in weak grid conditions.The traditional dual-loop control method with inverter-side current feedback is limited by its bandwidth and cannot achieve the desired stable dividing frequency.To address this problem,a new control method of capacitor voltage active damping is proposed.The method adopts a capacitor voltage feedback inner loop to enhance the damping effect of the system,and the additional capacitor voltage feedback loop reconfigures the system open-loop zero point to achieve the purpose of eliminating the reverse resonance peak.Theoretical analysis shows that the proposed method widens the system stability interval.It not only eliminates the harmonic amplification frequency domain but also maintains high robustness and control performance even with wide variations in grid impedance.Finally,the correctness of the theoretical analysis and the effectiveness of the method are verified by simulation and experiment.