Response of low voltage grids with connected prosumers to a voltage dip

Abstract

The increasing penetration of rooftop PV-systems modifies the reactive power flow through the distribution transformer. Additionally, the dynamic behaviour of the low voltage grid is mainly defined by the dynamics of the PV-systems and load devices. This paper studies the reactive power response of low voltage grids with connected prosumers to a voltage dip provoked by a three-phase fault in the superordinate grid. A detailed prosumer and PV-system model is used to analyse the reactive power contribution of a low voltage grid in stabilizing the situation during and after the fault. Three scenarios are considered: without PV-systems; with PV-systems; and with PV-systems upgraded with dynamic voltage support. Results show that, compared to the case without PV-systems, the integration of PV-systems increases the Q-flow from the medium into the low voltage grid and the voltages in low voltage grid. If PV-systems are upgraded with dynamic voltage support, the low voltage grid behaviour changes during the voltage dip: it produces reactive power thus supporting the voltage recovery process of the superordinate grid, but simultaneously, it has lower voltages. Furthermore, the post-fault stabilization process in low voltage grid is significantly delayed in this case.