For effective parallel operation with existing systems, it makes sense for grid-connected systems to fulfil the requirements placed on converters in accordance with VDE-AR-N 4105 as precisely as possible. This also includes static voltage support, which makes it possible to counteract the voltage increase caused by feed-in and to significantly increase the absorption capacity of distribution grids for decentralised energy systems. This motivates the investigations published here in the “Fuchstal-leuchtet” and “Verteilnetz 2030+” projects as to whether grid-forming systems are also capable of implementing the static voltage support methods in accordance with VDE-AR-N 4105. This is a major challenge, particularly due to the fact that grid-forming systems directly influence the voltage. In a previous work, the ability of a grid-forming inverter to realise a Q(V) characteristic curve in a laboratory environment in parallel operation with a grid-following inverter has already been demonstrated. In this work, the dynamic interactions of the two inverters are considered. This includes different start-up time constants of the Q(V) control and varying positions of the inverters in the grid. In addition, the reaction to rapid voltage changes is analysed.
Garn et al. (Sun,) studied this question.