Design and implementation of an LCL grid‐connected inverter based on capacitive current fractional proportional–integral feedback strategy

Abstract

The capacitive current feedback active damping strategy has a limited damping region. When the grid-side impedance is large, the digital control inductor–capacitor–inductor (LCL) grid-connected inverter system with grid-side current loop control and capacitive current feedback active damping cannot run stably. To address this issue, this study proposes an improved capacitive current feedback active damping strategy, namely the capacitive current fractional proportional–integral feedback strategy (CCFPIFS), which increases the upper-frequency limit of the system damping region and approaches to the Nyquist sampling frequency. Furthermore, this study analyses the constraints of fractional-order proportional–integral controller parameters to ensure the stability of the system. The simulation analysis is performed by Simulink. The experimental results are consistent with theoretical expectations. Consequently, the proposed CCFPIFS can not only achieve better control performance and improve the robustness of the LCL grid-connected inverter system, but also improve the output power quality of the system. This damping strategy can make the LCL grid-connected inverter system work stably under the environment of high grid impedance.