Harmonic Voltage Reduction by using Droop Controller in Inverters Parallel Operation

Microgrid technology makes possible coordination and effective use of different energy resources for supplying loads. In order to have synchronous operation between inverter resources during the occurrence of islanding condition, the use of droop controller structure would be beneficial. In this paper, the conventional droop controller is modified to divide proportional power between resources and cause accurate voltage setting in output resources. By providing a model for connected inverter to the nonlinear load, a harmonic droop controller has been designed. By droop controller related to each harmonic, the harmonic voltages are calculated and add to the reference voltage. Therefore the quality of the output voltage is improved. Then the inverter voltage control loop would be modified with resistance impedance in the presence of non-linear loads, so that, in combination with harmonic droop controller, THD of output voltage considerably reduced. Simulation results show the ability of suggested method in reduction of harmonic voltages in inverters parallel operation.