Estimation of voltage parameters for grid-connected inverters

The power quality of grid-connected inverters depends much on voltage parameters estimated by phase-locked loops. This paper proposes a robust technique for fast and accurate estimation of fundamental parameters of single-phase grid voltage under harmonics. The proposed technique bases on the least squares method using Levenberg-Marquardt algorithm to estimate the parameters of grid voltage. This does not base on interdependent loops offering stability and easy estimating process. It can also reject the negative effects caused by the presence of the dc offset as well as the harmonics. The simulation results in MATLAB/Simulink validated the robustness and accuracy of the proposed technique compared to the phase locked-loop basing on a second-order generalized integrator (QSG-SOGI).