自适应陷波滤波器的并网逆变器相位超前补偿方法

Phase lead compensation method of grid-connected inverter with adaptive notch filter

逆变侧电流反馈控制的LCL型并网逆变器广泛地应用于实际中,然而在数字控制下,控制延时改变了系统的相位特性,进而影响系统的稳定性。为此,提出了一种基于自适应陷波滤波器(adaptive notch filter,ANF)的相位超前补偿方法。首先,利用陷波器的相位超前环节对控制延时产生的相位滞后进行补偿,从而避免系统相位在谐振频率处穿越-180°,改善了系统的稳定性并增强其对弱电网的鲁棒性。其次,采用ANF算法对系统的谐振频率进行估计,并根据估计值动态调整陷波频率,扩大了谐振频率稳定区间,进一步提高了系统对LCL参数波动的适应能力。最后,对所提方法进行实验验证,结果表明:基于ANF补偿方案的并网逆变器稳定性良好,且相比传统的陷波方案,该方案对电网阻抗及LCL参数波动具有更好的鲁棒性,更利于LCL并网逆变器在弱电网工况下的控制。

The LCL-type grid-connected inverter with inverter-side feedback is widely used in practical applications.However,the system stability can be affected by the digital control delay which changes the system phase-frequency characteristics.Therefore,this paper proposes a phase lead compensation based on an adaptive notch filter(ANF).Firstly,the phase lag caused by the control delay is compensated by the phase lead of the notch filter,which avoids the system phase crossing-180°at the resonance frequency;thus,the system stability and its robustness to weak grids are improved.Secondly,the system resonance frequency is estimated by the ANF algorithm,and the notch frequency is dynamically adjusted according to the estimated value;hence,the stability range of the resonance frequency is extended,which enhances the adaptability of the system to LCL parameters variations.Finally,the proposed method is verified by experiments,and the results show that the grid-connected inverter based on the ANF scheme has good stability.Moreover,compared with the traditional notch scheme,the proposed scheme has better robustness to the grid impedance and the LCL parameters variations;thus,it is more conducive to the control of LCL-type grid-connected inverters in weak grids.