Pll for Single Phase Grid Connected Inverters

In grid connected applications the synchronization of output signals of the converters to be connected with grid parameters frequency and phase is of great importance. Different methods based on Fourier transforms, zero-crossing detection, Kalman filters, phase-locked loops (PLL) and others are used for this synchronization. This paper presents a new PLL for synchronization of the output current of single-phase grid connected inverters with the utility grid voltage. It is based on trigonometric transformations sine and cosine functions in a phase detector block. The proposed method’s simplicity and efficiency are proved by means of computer simulations and experimental analysis. The practical realization of the PLL is based on analog and digital programmable devices. Simulation and experimental results show good agreement with the results obtained by the theoretical analysis. Advantage of the proposed PLL is its insensibility to changes of the amplitude of the input signal after the synchronization has been achieved with its frequency and phase. Also, in the proposed PLL, the settling time both at a step change of frequency and phase is decreased. KeywordsDDS, FPAA, single-phase inverter, phase detector, phase locked-loop, utility grid, VCO