Improved reactive power sharing among photovoltaic inverters using Thévenin's impedance based approach

摘要

Unity power factor injection from rooftop photovoltaics (PVs) in residential distribution systems are creating voltage magnitude problems. One way to deal with this is to ensure reactive power sharing from PV inverters. However, the conventional droop based strategies lead to uneven reactive power contribution penalizing the PV inverters towards the end of the radial feeder. Instead, this paper proposes Thévenin's impedance based approach for higher degree of fairness in reactive power sharing among inverters. An iterative method is used to determine the Thévenin's equivalent impedance and hence the amount of reactive current injection from the inverter. The convergence property is verified using basics of circuit theory such as Thévenin's theorem and its dual Norton's theorem. Simulation results shows the efficacy of the proposed approach in a radial feeder with two inverters.