Nonlinear Controller Allowing the Use of a Small-Size DC-Link Capacitor in Grid-Feeding Converters

In this article, we propose an instantaneous complex power control (ICPC) for a grid-tied voltage-source converter, which has two important features: it allows injecting currents with low distortion to the grid, and it allows to significantly reduce the value of the dc link capacitor, which can potentially increase the reliability of the system and decrease its cost (considering different capacitor technologies). The proposal is based on finding the exact active power reference that the controller requires to keep the mean value of the energy in the dc link constant at all times. This means that, even when the loading conditions change, the mean value of the dc link voltage remains unchanged, allowing the reduction of the value of dc link capacitor. The proposed control scheme is validated both through simulations and experimental results.