A new control scheme for parallel-connected inverters taking into account the effect of line impedance is presented. The system presented here consists of two single-phase inverters connected in parallel. The control technique is based on instantaneous average current-sharing control that requires interconnections among inverters for information sharing. A generalized model of a single-phase parallel-connected inverter system is derived. The model incorporates the detail of the control loops that use a proportional-resonant controller, but not the switching action. The voltage- and current-controller design and parameters selection process are discussed. Adaptive gain scheduling is introduced to the controller to improve the current and power sharing for a condition, where the line impedance is different among the inverters. The simulation results show that the adaptive gain-scheduling approaches introduced improve the performance of conventional controller in terms of current and power sharing between inverters under difference line impedance condition. The experiments validate the proposed system performance.
Ahmed, K. H., Roslan , A. M., Finney , S. J., & Williams, B. W. (2011). Improved Instantaneous Average Current-Sharing Control Scheme for Parallel-Connected Inverter Considering Line Impedance Impact in Microgrid Networks. IEEE transactions on power electronics, 26(3), 702-716. https://doi.org/10.1109/TPEL.2010.2102775