Rethinking Band-Pass Filter on Frequency Coupling Effect in Single-Phase Voltage Source Inverter

Frequency coupling effect (FCE) commonly exists in single-phase converters, introducing complexity to the analysis and synthesis of single-phase inverter systems. Although the band-pass filter (BPF) has been widely used in controllers for filtering harmonic and damping improvement, this paper rethinks the effect of the BPF on FCE in single-phase inverters. The study reveals that the output impedance of the inverter equipped with a BPF remains almost unchanged, whether accounting for FCE or not, even under weak grid conditions. That is to say, when the BPF is applied, the output impedance without considering FCE can be used for accurate stability analysis and controller design. Furthermore, it is identified that a significant expansion in the stability regions of the single-phase inverter compared to control schemes without the BPF. Both simulations and experiments verify the effectiveness of the theoretical analysis results.