A New grid synchronisation scheme for a three-phase PV system using self-tuning filtering approach

This study presents a new control scheme for synchronisation of a photovoltaic (PV) system to a three-phase grid employing self-tuning concept. The proposed synchronisation approach is developed to mitigate load current harmonics, to extract maximum PV power and inject it into the grid. Maximum PV power is extracted using an incremental conductance-based algorithm for estimating the reference DC-link voltage of a voltage source inverter and a proportional–integral controller for regulating the actual DC-link voltage. In the proposed self-tuning filter (STF) algorithm, only a single module of STF is required to extract the fundamental components of load current and grid voltage thus reducing system size, complexity and overall response time. Simulation of the proposed system is carried out using MATLAB/Simulink followed by experimentation on a prototype of grid connected PV system developed in the authors' laboratory. The efficacy of the proposed STF control scheme is compared with a recently reported algorithm called improved linear sinusoidal tracer (ILST) and dual second-order generalised integrator (DSOGI). From the comparison with DSOGI and ILST, it is observed that the STF-based control scheme provides faster response and reduces total harmonic distortion of the grid current despite the distorted and unbalanced grid condition.