In this paper, we consider the problem of overvoltage arising in PV residential microgrids due to excessive power injection into the grid by the PV generators. We propose a decentralized optimal integral controller to curtail excess active power in order to avoid overvoltage. Considering the voltage and active power constraints, we show that the proposed controller leads to maximum power injection into the grid. We discuss the objective of fair power curtailment and show that it is in contrast with our objective of maximum power transfer. Finally, we present the performance of the controller through simulation studies.