A method of controlling the grid-side current of a single-phase grid-connected converter having an
LCL filter connected between the output of the converter and the grid. The method includes measuring a
grid voltage (vS) and at least one
signal in a group of signals consisting of a grid-side current (i0), a converter-side current (i1) and a
capacitor voltage (vC0). The method includes estimating the fundamental component (vS,1) of the
grid voltage (vS), forming a grid-side current reference (i0*), a converter-side current reference (i1*) and a
capacitor voltage reference (vC0*) for the grid-side current of the
LCL filter using the fundamental component of the
grid voltage (vS,1), forming estimates for the non-measured signals in said group of signals, forming a grid-side current difference term (ĩ0), a converter-side current difference term (ĩ1) and a
capacitor voltage difference term ({tilde over (v)}C0) from the differences between the references and measured / estimated values of said signals, forming an injection term for damping the
resonance of the
LCL filter by using an active damping injection mechanism (ADI), in which the grid-side current difference term (ĩ0), the converter-side current difference term (ĩ1) and the
capacitor voltage difference term ({tilde over (v)}C0) are used, forming an estimate of
harmonic distortion term ({
circumflex over (φ)}) using the grid-side current difference term (ĩ0), and controlling the output voltage (e) of the converter on the basis of the grid voltage, formed injection term and formed estimate of the
harmonic distortion term ({
circumflex over (φ)}) to produce a grid side (i0) current corresponding to the current reference.