Microgrids are attracting a great deal of attention as integrated renewable energy resource can benefit both the utility and the customers. The droop-control method is popular for the microgrid stable operation as it avoids circulating currents among the converters without using any critical communication between them. The distributed generators should have high speed to follow the reference given by the droop controller, otherwise the system will fluctuate and even black out. Renewable energy powered Distributed Generators (DGs) are mostly inverter-interfaced and controlled by PI controllers. The Particle Swarm Optimization (PSO) was used to optimize the PI parameters with the objective of high tracking speed of the Inverter-interfaced DGs. Simulation studies in Matlab demonstrate the effectiveness of the optimized control parameters.