Single-Stage SECS Interfaced With Grid Using ISOGI-FLL-Based Control Algorithm

This paper proposes an improved second-order generalized integrator with frequency-locked loop (ISOGI-FLL) based control scheme for a grid-connected solar photovoltaic (PV) array fed voltage source converter (VSC) to mitigate the power quality problems. The steepest descent algorithm based maximum power point tracking is used to achieve the crest power from a solar PV array to improve solar power generation (SPG) into the grid as well as to maintain dc bus voltage of the VSC. The ISOGI-FLL-based control scheme is very effective for grid currents balancing and harmonics mitigation, at a variation of SPG and unity power factor operation. Simulated results are demonstrated using MATLAB/Simulink for load unbalancing and variation in solar insolation. The effectiveness of the proposed algorithm is demonstrated based on comparative performance with conventional algorithms. Test results of a developed prototype show satisfactory performance for different operating conditions like grid currents balancing, photovoltaic-distribution static compensator (PV-DSTATCOM) mode, and DSTATCOM-PV mode at variable solar insolation. Moreover, total harmonic distortions of grid voltages–currents are achieved within the limit of the IEEE-519 standard.