Control scheme based on capacitor voltage second-order complex-vector feedforward for LCL-filtered inverter

Abstract

For an inverter with LCL filter, voltage at the point of common coupling (PCC) is equivalent to the filter capacitor voltage in practical applications. However, the PCC voltage background harmonics will cause the distortion of grid current. Some problems exist in the traditional methods for harmonics suppression, such as insufficient phase margin, increasing design complexity and computation burden. Thus, a scheme of second-order complex-vector feedforward (SOCVF) of capacitor voltage is proposed in this article. First, based on the vectorial principle, the active unit vectors of capacitor voltage were calculated. Then, its fundamental component was obtained by the SOCVF-function. Furthermore, the references of the grid current were obtained with the instantaneous power theory. Hence, the proposed scheme helps effectively dampen the LCL resonance to make the system stable, and works well at suppressing the injected grid current distortion simultaneously. Simulation and experimental results validated the effectiveness of the proposed scheme.