부산대학교 도서관

For the grid-connected inverter, phase-locked loop is generally adopted to obtain the voltage phase information in order to make the grid current be synchronized with the grid voltage. In the meantime, the grid-voltage-feedforward scheme is usually employed to improve the grid current quality. However, both of these two factors may cause negative impacts on the stability in weak grid. In this article, we focus on the LCL -type grid-connected inverter and aim to investigate the reasons for instability and optimize. In view of the existence of dual unstable factors, a synthesis-admittance-phasor scheme is proposed to analyze the influence mechanism of multiple admittances. And considering the attenuation effect of the bandpass link, the design goal of the bandpass link is determined according to the phase margin requirements, and the design process is further given. The results show that the grid-connected inverter with the optimally designed bandpass link can still work stably even against the wide grid-impedance variation.