Study of multi-objective photovoltaic grid connected system using SOGI-FLL and NL-SOGI-FLL-APF based DQ hysteresis method

This study reports on the results of an experimental investigation into a multi-objective nonlinear oscillator-based frequency-locked loop with an advanced pre-filter in a three-phase photovoltaic grid interface employing direct and quadrature hysteresis control for a distribution system. A reference voltage generation approach is also used to obtain the most power out of the solar array. In various case studies, including reactive and real power balance between load, grid, and photovoltaic systems under uncertain and varying solar power conditions, the proposed nonlinear second-order generalized integrator-based frequency-locked loop with an advanced filter performance is compared to a second-order generalized integrator-based frequency-locked loop. The proposed control enabled more stable operation and appropriate synchronization when grid voltages were distorted by the combined action of dc offset and harmonics. According to experiments, the suggested control achieves grid synchronization more correctly under abrupt changes in grid conditions and disturbances. The findings of an experimental laboratory prototype are confirmed using power quality indices for harmonic distortion assessment of source currents, as defined by the IEEE-519 guidelines.