A novel digital phase-locked-loop for single-phase grid-connected power generation systems

A novel digital phase-locked-loop (DPLL) method is proposed for single-phase grid-connected power generation systems in this paper. It consists of a grid voltage feed-forward network and a fictious instantaneous power feedback correction network. The fundamental signal of the grid voltage is extracted by a digital Butterworth filter to generate a unity sine reference signal for the feed-forward network, while only the signs of fictious instantaneous active and reactive powers are used to revise the phase shift of the unity sine reference signal by means of a real-time variable step-size control in the feedback phase correction network. The method is validated to have good dynamic and static performances through MATLAB simulations and experiments with a grid-connected photovoltaic (PV) power generation system under different conditions.