Modified Third Order Filter Based Solar Grid Interfaced System to Improve Power Quality Issues under Grid Voltage Distortion

This paper presents a modified third order filter (MTOF) for solar PV system with double stage topology under abnormal grid voltage conditions. MTOF elicits the fundamental component of the nonlinear load current, free from DC offset, inorder to obtain the reference magnitude of the grid current. Under unbalanced grid voltage conditions, it maintains sinusoidal unit templates using the estimated positive sequence voltages of the grid. These unit templates ensure balanced and sinusoidal grid current throughout the balanced and unbalanced grid voltages conditions. The peak power extraction from the solar photovoltaic array is achieved using an incremental conductance (INC) technique. The MTOF based control is simulated in MATLAB/Simulink. Moreover, it is tested using an experimental setup. The hardware results show the efficacy of the filter during the steady state and dynamic conditions such as imbalance in load and change in level of radiation. The harmonic distortions of the grid currents are complying to the IEEE-519 standards.