Advanced Power Sharing Scheme under Unbalanced and Nonlinear Loads in an Islanding Microgrid



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Active, unbalanced, and harmonic power sharing inaccurately between distributed generators (DGs) and voltage quality problems are critical issues under unbalanced and nonlinear loads in the micro grids. Thus, an advanced power sharing scheme with unbalanced and harmonic loads in islanding micro grid is presented to eradicate power sharing problems and reduce unbalanced voltage and harmonics distortion. The hierarchical control structure comprises primary and secondary levels. For improving voltage quality, a secondary controller is designed to manage compensation of unbalanced and harmonic voltage at point common coupling (PCC). The Primary controller consists of distributed generators local controllers. The local controllers mainly include power droop for sharing active and reactive power among DGs without communication, voltage and current controllers, and virtual impedance control loop. Virtual impedance loop for positive and negative sequences of fundamental and harmonic components is used to achieve better power sharing of reactive, unbalance and harmonic powers. The design procedure of the hierarchical control structure is discussed in detail. The proposed approach is able to operate in islanded micro grids for voltage quality enhancement. Effectiveness of the hierarchical power sharing scheme is presented on MATLAB/Simulation and the simulation results of the proposed method are provided to demonstrate that PCC voltage distortion decreased from 9.47% to 4.62% while reactive, unbalanced, and harmonic powers is shared proportionally among DGs after compensation.



Microgrid, Power sharing, Distribution generation, Virtual impedance, Droop control, Harmonic distortion