Modified LMS synchronization technique for distributed energy resources with DC-offset and harmonic elimination capabilities.

Grid synchronization techniques are needed to improve the distribution system's power quality with the Shunt Active Power Filter (SAPF). The traditional synchronization technique or the Phase Locked Loop (PLL) works well under ideal grid conditions; however, its performance deteriorates under non-ideal grid conditions. In this paper, a new scheme has been proposed to function as PLL. The Modified Least Mean Square (MLMS)-PLL has been proposed for tracking the phase angle under non-ideal grid conditions such as phase shift, frequency deviation, harmonics in the signal, DC offset and combinations of these grid voltage issues. The proposed method has added the advantage of DC-offset estimation and perfect synchronization template generation over conventional PLL. The MLMS-PLL algorithm precisely estimates phase, amplitude and frequency information and generates a synchronizing signal under abnormal grid conditions. The designed algorithm is extensively tested and shows advantages such as least steady-state error, faster dynamics and DC-offset rejection capability. Experimental findings of the proposed synchronizing technique show the effectiveness of the proposed technique and experimental results are also compared with other modern synchronization techniques. The application of MLMS-PLL for synchronization, reactive power compensation and harmonic elimination in a grid-tied PV system has been validated in the experimental prototype.