In this paper, a robust adaptive direct power controller (RADPC) is designed for voltage source inverters (VSIs) in grid-connected photovoltaic (PV) systems. The proposed scheme is designed to ensure the robustness of three-phase grid connected PV systems against both parametric uncertainties and external disturbances. The dynamical model of grid-connected PV systems is developed in terms of power (active and reactive) equations where parametric uncertainties are captured by considering all parameters as unknown and measurement noises are considered as external disturbances. The proposed scheme directly controls the active and reactive power injection into the grid using the estimated values of parameters. The proposed RADPC also ensures the desired tracking of the DC-link voltage. Simulation studies are conducted to validate the performance of the proposed scheme and simulation results have revealed that the proposed scheme outperforms the existing sliding mode controller (ESMC).