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 fourwireinverter in the presence of unbalanced and nonlinear loads is investigated. Theproposed control method has two current internal and voltage external control loops.Current internal loop has a proportional-resonant controller. The voltage external loophas two parts including voltage controller and load current sharing. In the currentsharing part, first output of voltage controller is broken to harmonic and then is sharedbetween the inverters with the new strategy: 1) Supply of zero sequence load currentby 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 currentpositive orders evenly between the inverters. The proposed system is capable to feedbalanced, unbalanced and nonlinear loads and provides proper sinusoidal voltage atboth ends of the loads by exact sharing of power between parallel inverters. Thesimulation results show the proper functioning of the proposed system.

Keywords:

Four-leg inverter , Parallel inverter , Harmonic current sharing , Total Harmonic Distortion