A Normalized Adaptive Filter for Enhanced Optimal Operation of Grid-Interfaced PV System

This article presents a grid-connected single-stage photovoltaic (PV) system using an adaptive normalized notch filter (ANNF). An unknown time-varying fundamental frequency is precisely estimated from a normalized notch filter and consequently, the fundamental load component is extracted using this algorithm. The convergence of the algorithm is independent of both amplitude and the frequency of the fundamental component, and therefore, this algorithm is robust to these changes in the load current. The adaptive estimation of fundamental load current with perturbations on load/grid side system is well analyzed. The ANNF based control strategy is not only efficient in fundamental extraction, however, it also achieves the objectives of supplying real power to the grid, grid currents balancing, and power factor correction. Moreover, this algorithm is robust to harmonic/ distorted/ unbalanced grid voltages caused at far radial ends in the weak distribution network. Elaborated simulation results are presented to show the effectiveness of the strategy. A prototype is developed to validate this control strategy at various perturbations. Under all operating conditions, test results are found satisfactory.