This work introduces a novel damped fifth-order generalized integrator (DFOGI) based control algorithm for grid-integrated solar photovoltaic (PV) system. Moreover, for GMPPT (Global Maximum Power Point Tracking), HPO (Human Psychology Optimisation) algorithm is used. Here, a three-phase three wire, single-stage topology of grid-integrated partially shaded PV array is implemented. Global maximum power peak searching behavior of HPO algorithm is very rapid and accurate, which gives a satisfactory steady-state and dynamic performances, even in rapid solar irradiance change condition. The prime objective of proposed DFOGI control is to accurately transfer the solar power to the grid at unity power factor, even when grid suffers from abnormal and adverse conditions. During these conditions, on the grid side, the power quality is maintained, where the proposed control technique provides power factor correction, and harmonics mitigation. The proposed techniques are modeled, and their performances are verified experimentally on a developed prototype, in solar insolation variation conditions, as well as in different grid disturbances such as over and under-voltage, phase imbalance, harmonics distortion in the grid voltage etc. Test results have met the objectives of the proposed work and parameters are under the permissible limit, according to the IEEE-519 standard. © 2019 Institution of Engineering and Technology. All rights reserved.