Modelling of low-voltage grids with high PV share and Q(U)-control

Abstract

: Climate challenges foster the integration of rooftop photovoltaic (PV) appliances. The associated inverters are often equipped with local Q ( U ) control to mitigate the voltage limit violations in low-voltage feeders. Their presence strongly modifies the behaviour of low-voltage grids. The common lumped model of the latter, which is used for load flow analysis in medium-voltage level, cannot describe their new behaviour. In this study, two lumped models of low-voltage grids are analysed and compared: the common or simplified one that does not consider the effect of the grid itself and the inverters ’ different working points in the Q ( U ) characteristic; and the exact one. Power flow simulations are performed in low-and medium-voltage test grids for maximal PV production. Results reveal high errors of the simplified lumped model that lead to incorrect power flow in medium-voltage grid.