Multi-resonant FLL-based control algorithm for grid interfaced multi-functional solar energy conversion system

This study presents a single-stage solar energy conversion system tied to a three-phase grid using a multiple second-order generalised integrator frequency locked loop (MSOGI-FLL)-based control algorithm to improve power quality of the distribution system with DSTATCOM (Distribution Static Compensator) capabilities. The estimated perturb and observe algorithm is used for maximum power point tracking to obtain maximum power from a solar photovoltaic (PV) array. The MSOGI-based control algorithm is used for load balancing, harmonics elimination, and power factor correction and delivering active power to the grid. The MSOGI-FLL has advantages of adaptive nature with frequency variation and better harmonics filtering capabilities when compared with conventional algorithms, which is demonstrated with frequency domain analysis. The comparative performance of amplitude extraction capabilities with conventional algorithms is also demonstrated. This system configuration is simulated in MATLAB®/Simulink. The proposed control algorithm is verified on a developed prototype for various conditions like variable solar insolation level, load balancing, reactive power compensation, PV to DSTATCOM mode, and DSTATCOM to PV mode. The total harmonic distortions of grid voltages and currents are found well within the limits of an IEEE-519 standard.