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Abstract

Nowadays, the use of grid-integrated inverter proton exchange membrane fuel cell (PEMFC) systems is becoming more prevalent due to their efficiency and favorable environmental effects. Switching the grid-connected inverters causes high-frequency harmonics, which are eliminated using LCL filters. These filters are susceptible to instability when their resonant frequency is affected by changes in network impedance. Active damping methods are used to weaken the resonance of LCL filters. However, the grid-connected inverter is prone to be unstable under grid impedance variations due to the negative equivalent resistance resulting by digital control delays. As a solution to this problem, the capacitor-current proportional-integral (PI) positive feedback active damping approach is suggested in this study. It can provide a positive equivalent resistance almost within the Nyquist frequency, i.e., the entire controllable frequency range. As a result of the proposed method, the grid-connected inverter achieves strong stability against grid impedance variations. In this study, a PEMFC stack is used to produce and inject power into the weak grid using the proposed controller. MATLAB/Simulink simulation results are presented to verify the validity of the proposed method. The simulation results show that the proposed method is stable against changes in grid impedance and PEMFC parameters, and provides a good performance.

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