a new control strategy to parallel operation of three-phase three-wire inverter and three-phase four-wire inverter

in this paper, parallel operation of three-phase three-wire inverter and three-phase fourwire inverter in the presence of unbalanced and nonlinear loads is investigated. the proposed control method has two current internal and voltage external control loops. current internal loop has a proportional-resonant controller. the voltage external loop has two parts including voltage controller and load current sharing. in the current sharing part, first output of voltage controller is broken to harmonic and then is shared between the inverters with the new strategy: 1) supply of zero sequence load current by four-leg inverter and sharing the rest of orders evenly between two inverters. 2) supply harmonic orders of load current by four-leg inverter and sharing load current positive orders evenly between the inverters. the proposed system is capable to feed balanced, unbalanced and nonlinear loads and provides proper sinusoidal voltage at both ends of the loads by exact sharing of power between parallel inverters. the simulation results show the proper functioning of the proposed system.