Current Quality Improvement of Fuel Cell Power Conditioning System Connected to Weak Network

In grid-connected inverters, the quality of the grid-injected current is seriously affected by the point of common coupling (PCC) voltage harmonics. In general, to solve the problem, an impedance deformation method based on feedforward of the PCC voltage is applied to the grid-tied inverter. However, using this method causes a 90-degree phase delay in the output impedance of the inverter, which phase delay challenges the compatibility of the weak grid-tied inverter. This paper proposes a new virtual impedance shaping method based on frequency segmentation to solve this problem and improve the injection current quality of the fuel cell power optimization system connected to the weak network with an LCL filter. Different coefficients are employed in the proposed method the fuel cell power conditioning system connected to the weak grid output impedance in various frequency bands. Primary principles, theoretical analysis, design parameters, and application evaluation are investigated in detail. In the proposed design because of the fuel cell-based grid-connected inverter is capable of simultaneously targeting points of common coupling voltage harmonics and is compatible with a wide range of weak grid impedance. Finally, the simulation of the fuel cell power conditioning system connected to a weak grid has been conducted in the Simulink/MATLAB environment. The results obtained from the theoretical analysis and simulation confirm the efficiency and optimal performance of the proposed method in injecting fuel cell power into the grid and improving the quality of injected current along with stability for the weak network.